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zODIAC A digital companion to Night Sky
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Find your zodiac symbol
e 21 to July 22
Jun t 2 us o 3 t2 2
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ly Ju Se
pte m be r 23 Oc to tob er 22
Libr a
t 23 Augus to 22 ber m e t S ep
o Virg
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Can cer
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ini
Decem ber 22 to January 19
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Marc h2 1 to April 19
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2 er 2 Novemb to 1 er 2 Decemb
s riu Sagitta
Ophiuchus The 13th constellation
20
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What is the zodiac? A starry band
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Arie s
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Look up into the sky on a clear night and you will see thousands of twinkling stars. Keep looking and you may be able to detect constellations, or patterns, in the sky. Click on a button to discover more about the constellations of the zodiac!
What is the zodiac? [A starry band] It takes Earth a year to orbit the Sun. During this time, it appears from Earth as if the Sun is moving along a path on the celestial sphere. We call this path the ecliptic. The 12 major constellations that the Sun passes through each
year form a band known as the zodiac. The zodiac constellations share their names with star signs, which are used to make horoscopes. The dates when the Sun is in a zodiac constellation are different from those given to star signs.
Horoscopes What sign are you?
Seeing the zodiac Stargazing
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Constellations video
Chinese dragon The ancient Chinese divided the zodiac band into 28 mansions, or regions. Seven of these mansions were ruled by the Azure Dragon of the East.
Direction of the sky’s daily rotation
Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpius
Sagittarius
Capricornus
Aquarius
Pisces
Seeing the zodiac [Stargazing] If you can get far away from city lights on a clear, moonless night, the zodiac constellations are easy to see. Even in a city, some stars will be visible if you stand away from the brightest lights. Avoid looking at lights—even flashlights—for at least ten minutes, and your “night vision” will improve. To find out where and when each constellation can be seen, check the Internet for up-to-date star maps for your location. Cancer [The Crab]
Leo [The Lion]
Aries [The Ram] Aries is small, fairly dim, and most easily seen in December. The best way to find it is by locating the constellation of Triangulum, a small triangle of stars. Aries is between Triangulum and the horizon.
Virgo [The Virgin]
Libra [The Scales]
Cancer can be a tricky constellation to find, but March is the best month to search for it. On a dark night, you can just see the Beehive, a globular cluster, which is the Crab’s head. Leo is easily seen on April nights. The bright star Regulus marks the Lion’s front paws.
Virgo is best seen in May. Spica, the brightest star in the constellation, represents an ear of corn that the Virgin is holding.
Capricornus [The Sea Goat]
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Taurus [The Bull]
Gemini [The Twins]
Best seen in January, Taurus is easy to spot because of its V shape. The reddish star Aldebaran is one of the Bull’s eyes.
Gemini is most easily seen in February. The two bright stars Castor and Pollux (which has a slight orange tinge) mark the heads of the Twins.
Scorpius [The Scorpion]
Sagittarius [The Archer]
A difficult constellation to make out, Libra is best seen in June. The star Zubeneschamali has a faint green color.
Aquarius [The Water Carrier]
The best month to spot Scorpius is July. To find this dim constellation, look for the bright red star Antares, which marks the head of the Scorpion.
Best seen in August, Sagittarius is crossed by the Milky Way, which is easy to see if the night is really dark.
Pisces [The Two Fish]
Capricornus is easiest to see in September; it can be identified by the bright double star at the western end, called Algiedi (the Kid).
The three stars of the water jug, shown here at top center, are the easiest part of Aquarius to identify. Aquarius is best seen in October.
Best seen in November, Pisces is close to a large square of bright stars that is part of the constellation Pegasus, the Flying Horse. One of these four stars lies between the Two Fish.
Horoscopes [What sign are you?] Some people, called astrologers, believe that the positions the Sun, Moon, stars, and planets are in when you are born can influence your personality. Astrologers make horoscopes—charts that map these cosmic bodies. They have divided
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the calendar into 12 star signs, named after the zodiac constellations. The 12 signs are grouped into 4 elements: fire, water, earth, and air. Each sign is related to a basic personality type. Look up your birth date to discover your sign.
Key Fire sign
Earth sign
Water sign
Air sign
The elements Friendly groups January
Capricorn
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Aries
February Aquarius
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Scorpio
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Sagittarius
Capricorn
The elements [Friendly groups] Astrologers divide the 12 zodiac star signs into 4 elements, or groups: fire, water, earth, and air. Each element represents a different aspect of personality. Fire represents spirit and energy; water, emotion and nurturing; earth, material things and security; and air, intellect and
Fire
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communication. Astrologers believe that people of the same element share basic character traits and are likely to get along with one another. So Leos have a lot in common with fellow fire people Arians and Sagittarians, and Cancers form easy friendships with Scorpios and Pisceans.
water
Earth
Air
Aries/Leo/Sagittarius
Cancer/Scorpio/Pisces
Taurus/Virgo/Capricorn
Gemini/Libra/Aquarius
Fire people are bright and strong, and they like to take control. They are the energy boosters of the zodiac.
Deeply emotional water people are in tune with their environments. They are caring and sensitive.
Earth people are the rocks of the zodiac: They are practical, reasonable, and hardworking.
If you need something said or written, ask an air sign: Air people are the communicators of the zodiac.
celestial sphere
noun
The imaginary sphere on which the stars seem to be projected, with Earth at the center of the sphere. In ancient times, the sky was often pictured as a sphere that rotated from east to west once every 24 hours. Since all astronomical bodies (except for the members of the solar system) are so far away from Earth that they appear fixed, or unmoving, in the sky, the idea of the sky as a sphere around Earth remains a useful one for astronomers. The celestial sphere’s apparent rotation is produced by the rotation of Earth on its axis; if Earth’s North and South Poles are projected out toward the celestial sphere, they become the points around which the sphere seems to rotate.
constellation
noun
Any one of many divisions of the sky described by astronomers, or the patterns of stars within these divisions as seen from Earth. Many constellations were named by the ancient Greeks after objects, animals, or mythological heroes. There are 88 constellations recognized by astronomers today, including Lyra (the Lyre), Ursa Major (the Great Bear), and Orion (the Hunter). Of these, 12 are zodiac constellatons—star patterns that the Sun passes through each year. The Sun also passes through Ophiuchus (the Serpent Bearer), although this constellation is not included in the zodiac.
ecliptic
noun
The path that the Sun appears to trace around the sky, or celestial sphere, each year. Twelve of the constellations around the ecliptic make up the zodiac. The Sun also passes through a thirteenth constellation, Ophiuchus.
horoscope
noun
A chart showing the positions of the Sun, Moon, stars, and planets at the time of a certain event, such as a person’s birth. Some people believe that a horoscope can be used to learn about a person’s character and predict events in his or her future.
zodiac
noun
The 12 ancient constellations that the Sun passes through as it moves along its path each year. The constellations are: Aries, the Ram; Taurus, the Bull; Gemini, the Twins; Cancer, the Crab; Leo, the Lion; Virgo, the Virgin; Libra, the Scales; Scorpius, the Scorpion; Sagittarius, the Archer; Capricornus, the Sea Goat; Aquarius, the Water Carrier; and Pisces, the Two Fish. Originally, all the constellations of the zodiac represented animals or people. In fact, the word zodiac comes from the Greek word zoidiakos, meaning “circle of living things.” Libra was for centuries a part of Scorpius called Chelae (the Claws), but it was made a separate zodiacal constellation in about 50 bce.
Aries [The Ram]
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Aries is a faint constellation that is hard to identify in the night sky. Two thousand years ago, it was the location of the vernal equinox, the point at which the Sun moves from the southern half of the celestial sphere to the northern one each year. This point has now moved on and is currently in Pisces, but Aries is still known as the first sign of the zodiac. In Greek mythology, a ram with a golden fleece carried a girl named Helle across the sea. Helle fell off and drowned, and the channel became known as the Hellespont, or the Sea of Helle. The ram was sacrificed, and its fleece later featured in the tale of Jason and the Argonauts. This is the ram that the constellation Aries represents. The Sun is in Aries from late April until the middle of May.
PERSEUS Hamal Aries is identified with the Greek god Zeus. The brightest star in Aries is Hamal; there are at least eight ancient Greek temples that were built to align with the rising or setting of this star. Hamal is 66 light-years from Earth.
TRIANGULUM
Hamal
Sheratan This supergiant star, whose name means “the two signs,” is extremely rich in metals, with three times the normal amount of iron.
ARIES ECL
TAURUS
IPT
Sheratan Mesarthim
PISCES
IC
Mesarthim This is a double star; its two components are almost the same color and brightness.
CETUS
The star
Sheratan
is about
ARIES
times larger than our Sun
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Aries is a ram.
So you’re an Arian? Find out what Arians are like.
[ ] Aries
Taurus
Gemini
Cancer
Aries gallery Leo
Virgo
Libra
Scorpius
Mira Ram 90° N to 60° S December, after sunset 39 Hamal, Sheratan, 41 Arietis, Mesarthim NGC 695, NGC 697, NGC 772, NGC 972, NGC 1156
Sagittarius
Capricornus
Aquarius
Pisces
Aries gallery
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NGC 695 is another galaxy bearing the marks of a past encounter, which changed the pattern of its spiral arms and triggered bursts of star formation.
This is a view of Aries with the main stars artificially brightened so that the shape of the constellation can be easily seen.
When galaxies pass one another, their shapes twist and shift as a result of their tangling gravitational fields. The enlarged spiral arm of Arp 78 is evidence of a past encounter, which also caused the births of the many clusters of young stars there.
Stars are born deep within vast clouds of dust and gas, called nebulae. The edges of this nebula are marked by clouds of dust, made long ago in the extended atmospheres of supergiant stars.
March 21–April 19 Like their symbol, the ram, Arians are energetic and determined. They put their hearts into all that they do, and they dislike hesitation and delays. Arians act on impulse and don’t always look before they leap.
Learning
Parties
Fast-thinking Arians are quick on their feet when it comes to grasping new ideas. But they can be less patient with others who are a little slower.
“Play hard and work hard” is the Aries motto. Arians like to be the life and soul of the party, and they brim over with enthusiasm.
Opinions
Sports
Famous Arians:
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Maya Angelou April 4
Leonardo da Vinci April 15
Lady Gaga March 28
Emma Watson April 15
Naturally talkative, Arians have no trouble expressing their opinions. They’re quick to stick up for themselves if they feel bullied or ignored.
Competition—bring it on! Arians love to excel, which may make them good at sports. This is a great way for them to use up excess energy.
Action!
Ego
Fast and furious— that’s how Arians like it! They love to start things off and get the ball rolling, but sometimes they can find finishing something to be a drag.
Arians like to be first. Superconfident, they love being the center of attention. They can easily take over, so they sometimes need to be reminded to think about other people, too.
Double star A double star is two stars that look as if they are close to each other in the sky when viewed from Earth. There are three types of double stars. Binary stars are stars that are bound together by gravity. They can be visual binaries, in which the two distinct stars can be viewed through a telescope, or nonvisual binaries, in which the stars are not individually visible but astronomers can deduce that they are both present, based on the behavior of the binary star. The third type of double star is the optical double. In this case, the two stars are actually far apart, but because they appear in a line when viewed from Earth, they look like they are close together. Sirius, the Dog Star, is the brightest star in the sky. If you look at Sirius through a powerful telescope, you will see that there is a white dwarf (called Sirius B) orbiting a main-sequence star (Sirius A). This means that Sirius is a visual binary. Algiedi, or Alpha Capricorni, in the constellation Capricornus, is an optical double. It is made up of two stars, Prima Giedi and Secunda Giedi, which are over 500 light-years apart.
This is an artist’s impression of the Kepler-35 planetary system. The two stars of Kepler-35 orbit each other every 21 days.
the percentage of stars in the Milky Way that are not single stars
Supergiant star Supergiants, the brightest known stars, generally have absolute brightnesses 10,000 times that of the Sun. The brightest supergiants are sometimes known as hypergiants. Supergiants are stars with masses typically ranging from 10 to 100 times the mass of the Sun, and radii from 20 to 1,000 times the radius of the Sun. Because of their enormous size, supergiants have relatively short life spans. There are different colored supergiants, from blue (extremely hot) to red (relatively cool). Several stars familiar to the naked eye are supergiants, including Antares (Alpha Scorpii), Betelgeuse (Alpha Orionis), Canopus (Alpha Carinae), Deneb (Alpha Cygni), and Rigel (Beta Orionis).
The Tarantula Nebula has a cluster of bright blue supergiant stars at its heart.
(30,000–50,000°C):
the surface temperature
of a blue supergiant
celestial sphere
noun
The imaginary sphere on which the stars seem to be projected, with Earth at the center of the sphere. In ancient times, the sky was often pictured as a sphere that rotated from east to west once every 24 hours. Since all astronomical bodies (except for the members of the solar system) are so far away from Earth that they appear fixed, or unmoving, in the sky, the idea of the sky as a sphere around Earth remains a useful one for astronomers. The celestial sphere’s apparent rotation is produced by the rotation of Earth on its axis; if Earth’s North and South Poles are projected out toward the celestial sphere, they become the points around which the sphere seems to rotate.
equinox
noun
One of the two points of intersection between the ecliptic (the Sun’s apparent annual path) and the celestial equator (the equator of the celestial sphere); also, the two moments in each year when the Sun is exactly over the Equator, and day and night are therefore of equal length. In the Northern Hemisphere, the vernal, or spring, equinox occurs about March 21, and the autumnal equinox occurs about September 23. In the Southern Hemisphere, these dates are reversed.
Taurus [The Bull] Taurus, the Bull, is one of the oldest recorded constellations. The ancient Greeks decided that it depicted the god Zeus, who took the form of a bull to kidnap Europa, a Phoenician princess. Only the head and part of the body of the bull are shown in the constellation. The constellation contains two well-known star clusters, plus a number of other notable objects, including a unique variable nebula and the Crab Nebula, which was produced by a supernova seen in 1054 ce. The Taurid meteors appear from the direction of Taurus each year around November 4. The Sun is in Taurus from the middle of May until late June.
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The Pleiades (M45) Known as the Seven Sisters, the Pleiades is a cluster of at least 100 stars. It is by far the brightest cluster in the sky.
Alnath
PLEIADES
TAURUS
NGC 1746
M45
M1
Crab Nebula (M1)
NGC 1647
This, the most studied of all nebulae, is a living museum of stars in all stages of development.
ECLIP
Aldebaran
HYADES
TIC
ORION
Aldebaran
The Hyades, a V-shaped cluster of over
PERSEUS
AURIGA
A bright, reddish variable star, 65 light-years from Earth, Aldebaran sometimes MONOCEROS represents the eye of the Bull.
ERIDANUS stars, is located behind Aldebaran, the Bull’s eye TAURUS
The symbol for Taurus is a bull.
So you’re a Taurean? Find out what Taureans are like. Aries
[] Taurus
Gemini
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Crab Nebula video
Cancer
CANIS MAJOR
LEPUS
Taurus gallery Leo
Virgo
Libra
Scorpius
Bull 90° N to 65° S January, after sunset 17 Aldebaran, Alnath, Alcyone, Zeta Tauri M1, M45, NGC 1647, NGC 1746, NGC 2259
Sagittarius
Capricornus
Aquarius
Pisces
Taurus gallery
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The Crab Nebula, M1, is an expanding mass of dust and gas left behind by a supernova explosion. A regular pulsing radio signal from within it is due to a type of fast-spinning star called a pulsar.
The Pleiades (M45) is one of the open clusters closest to Earth. It looks slightly hazy because it is passing through a dust cloud.
Cool stars and warm cosmic dust glow brightly at infrared wavelengths—waves in the light spectrum that are longer than those of visible light. This is the star cluster NGC 2259 in infrared light. Since infrared light passes through some dust clouds that block visible starlight, it makes some stars that are otherwise invisible visible to us in this image.
Aldebaran, here seen through Saturn’s ring system, is one of the brightest stars in the sky. It is a red giant about 45 times the diameter of the Sun.
April 20–May 20 Represented by Venus, the planet of love, Taureans follow their hearts. They are solid and dependable, and they like everything to be just so. Consequently, they can find it hard to cope with insecurity and change.
Creativity
Jealousy
Artistic and practical, Taureans are good at making things with their hands. The sense of touch—how things feel—is very important to them. They are often musical, too.
Taureans have strong feelings; once you win their friendship, it’s yours forever. However, this also means that they can be possessive, and jealous of your other friendships.
Friends
Change
Famous Taureans:
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David Beckham May 2
Ella Fitzgerald William Shakespeare
April 25
Adele May 5
April 23
If your best friend is a Taurean, you know you can rely on him or her. This is the most dependable sign in the zodiac. A Taurean is loyal and affectionate and won’t let you down.
Taureans love routine. They like everything to be familiar, and they can get thrown off balance if things become complicated or plans change.
Persistence
Luxury
Hardworking and determined, Taureans see things through to the bitter end. They stick to things when others give up, and they like to make sure that every last detail is right.
Taureans like their comforts. They spoil themselves at every opportunity. Good food, pretty things— Taureans just can’t get enough. They want nothing but the best.
Star cluster Star clusters are groups of stars. They are held together by gravity. Astronomers believe that about 1 in every 100,000 stars is in a cluster. All of the stars in a cluster were born together and move through space at the same speed. Astronomers compare the brightness and color of the stars in a cluster and this tells them how old the cluster might be. There are two types of star clusters— open clusters and globular clusters. They are found in different parts of the Milky Way galaxy and other galaxies, and they have different types of orbit. Open clusters live along the thin, flat disk of the Milky Way. They orbit close to its center in nearly circular paths. Globular clusters live in an outer halo around the Milky Way; their paths around the central point of the galaxy are large ovals. This image shows an open cluster of stars within the Soul Nebula.
the age of
some globular clusters
Supernova A type 1 supernova is a star that explodes. When it does so, it suddenly increases in brightness by a factor of many billions; within a few weeks, it slowly fades. As a star nears the end of its life, it keeps shining by burning increasingly heavy elements. Eventually, the star’s core is turned into iron, triggering its final, explosive collapse. The star blasts apart, tossing heavy elements into space. In many cases, a neutron star or a pulsar (a rapidly spinning neutron star) is left behind after the explosion. In our galaxy, the Milky Way, a supernova may be observed by the naked eye only once every few hundred years. In 1054, Chinese astronomers observed the “guest star” that created the Crab Nebula, visible in Taurus. European astronomers Tycho Brahe and Johannes Kepler observed supernovae in, respectively, 1572 and 1604. In 1987, a supernova in the Tarantula Nebula of the Large Magellanic Cloud was easily visible from the Southern Hemisphere.
During a supernova explosion,
elements are blasted into space at speeds of This shows the remains of a supernova called RCW 86, which was witnessed and described by the Chinese in 185 ce.
miles (1,600 km) per second
meteor
noun
The streak of light—also called a shooting or falling star— produced by the vaporization of debris entering Earth’s atmosphere from space. While still in space, the debris is known as a meteoroid. A large and abnormally bright meteor is called a fireball, and an exploding fireball is called a bolide. Larger meteors may not be completely vaporized; particles called meteorites may crash onto Earth’s surface and form craters.
variable star
noun
A star that varies in brightness, color, or magnetic field strength. There are two types of variable star: eclipsing variables and physical variables. An eclipsing variable is a binary star whose brightness changes when one of its orbiting components passes in front of the other, blocking some of the stars’ combined light from reaching Earth. Physical variables are single stars that change in brightness, for various reasons; for example, they may expand and contract.
Gemini [The Twins] Gemini is thought to represent a pair of people— or of gods, peacocks, gazelles, or even sprouting plants. According to Greek legend, the twins are not twins at all, but the half brothers Castor and Pollux, the sons of Leda, queen of Sparta. Castor’s father was human, while Pollux was the son of Zeus. The Greeks seem to have been the first to regard Gemini as a constellation that protected sailors, associating it with Saint Elmo’s fire, an electrical glow that sometimes appears on ships in stormy weather. Every year around December 14, the Geminid meteors stream from the direction of this constellation, often making the most spectacular display of the year. The Sun is in Gemini from late June to late July.
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LYNX Castor
AURIGA
Many stars are double, and some are triple or quadruple, but Castor is the brightest example of a six-in-one star, which is very rare. Two stars are in orbit around each other, both orbited by a third. And all three of these stars are themselves doubles.
GEMINI
Castor Pollux
M35 galaxy This galaxy is an open cluster—that is, its components are widely separated. It is fairly bright and contains several hundred stars.
IC
ECLIPT
NGC 2392
ORION
Eskimo Nebula
Alhena
This planetary nebula, also known as NGC 2392, is about 3,000 light-years from Earth.
CANIS MINOR
The Gemini star HYDRA
is approximately 220,000 times the size of our Sun
Aries
Taurus
[ ] Gemini
Cancer
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Gemini gallery Leo
Virgo
MONOCEROS
Procyon Gemini
The symbol for Gemini is twins.
So you’re a Gemini? Find out what Geminis are like.
TAUR
M35
Libra
Scorpius
Twins 90° N to 60° S January to February, after sunset 30 Pollux, Castor, Alhena, Tejat Posterior M35, Eskimo Nebula
Sagittarius
Capricornus
Aquarius
Pisces
Gemini gallery
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M35 is a scattered group of stars known as an open cluster. It contains several hundred stars and, from Earth, lies in the opposite direction from the center of the Milky Way galaxy.
M44
Pollux
Castor
Mars
Procyon
The Eskimo Nebula, or NGC 2392, is a planetary nebula that is unusual in several ways: It has a much brighter central star than other such nebula do; it has two shells, one inside the other; and it has unique orange streaks in its outer shell. The Eskimo Nebula got its name because it looks a little like a face in a fur-lined hood.
This image shows a whole range of astronomical objects, including the globular star cluster M44, bright stars Procyon, Castor, and Pollux, and Earth’s neighboring planet Mars.
May 21–June 20 Like their sign, the twins, Geminis have two sides to their personalities. They are outgoing, talkative, and fun loving. But they also have a serious, thoughtful side. Geminis keep you guessing, but at least life is never boring!
Travel
The grass is always greener on the other side if you’re a Gemini. Geminis love to travel, and they are always eager to see new places and meet new people.
Communication
Geminis love to talk. They love words, and they are witty and amusing. They are good at expressing themselves in writing, too.
What’s new?
Friends
Famous Geminis:
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Morgan Freeman June 1
Marilyn Monroe Rafael Nadal
June 1
Anne Frank June 12
June 3
Smart Geminis find it easy to understand new ideas and pick up skills. They are always up for a challenge, but because they love variety, they can easily get bored.
As expert communicators, Geminis make friends easily. They are kind and loving, but they can have short attention spans. They may be better at talking than listening.
Sports
Career
Geminis love to play games. With their agility, flexibility, and quick reaction times, they are particularly good at sports such as basketball, tennis, and volleyball.
Any job that involves communication will suit a Gemini. Since they are excellent at languages, Geminis love work that involves foreign travel. Naturally persuasive, they are also good at selling things.
Nebula A nebula is a vast cloud of dust and gases. Even though a few bright nebulae can be seen with the naked eye, astronomers use telescopes to study them. Nebulae are classified into three general types—diffuse nebulae, planetary nebulae, and nebulae formed by supernovae, or exploding stars. Diffuse nebulae, the most common type of nebula, look like ragged clouds. Hot stars within a diffuse nebula make its dust and gases glow, and some glow very brightly. These bright nebulae are called emission nebulae. The hot gases in emission nebulae glow with colors. In photographs, these nebulae often look red, because they are very rich in hydrogen, which gives off red light. Some planetary nebulae are circular in shape. Although they are not actually planets, they are called planetary because they look like planets when seen through a low-powered telescope. A planetary nebula shines because of the star at its center. The star is old, and its hot core is exposed. The nebula forms as the star’s outer layers of gas spew outward. A star that explodes so forcefully that it is almost completely destroyed is called a supernova. The explosion hurls out threadlike filaments of hot gas that had once made up the atmosphere of the star, and a nebula forms. An example of a nebula formed by a supernova is the Crab Nebula.
The Rosette Nebula, a star-forming region more than 5,000 light-years away, is in the constellation Monoceros.
Open cluster An open cluster is a group of stars held loosely together by gravity. Most contain between 100 and 1,000 stars. Open clusters are quite small; most are only 30 light-years across. Astronomers have found open clusters exclusively in spiral and irregular galaxies, which are areas of active star formation. Open clusters are younger than globular clusters. The oldest are about 100 million years old, and most are much younger. Their stars all formed from the same giant molecular cloud or nebula. They also contain 100 times more heavy elements than are found in globular clusters. These came from generations of stars that died long ago. One of the nearest and most important open clusters is the Hyades. Astronomers have used several methods to measure this cluster’s distance from Earth and have found that it lies about 160 light-years away. They now use this knowledge to calculate other distances across the galaxy. We can easily see the Hyades in the night sky— it lies in the constellation Taurus. Nearby appears another important cluster, the Pleiades, also called the Seven Sisters. This cluster is 424 light-years from Earth and contains between 250 and 500 stars.
More than the number The Pleiades is an open cluster of stars in the constellation Taurus.
of open clusters
discovered in the Milky Way
orbit noun The path that a comet, planet, or other satellite follows around another object due to gravity. Earth, along with all of the other planets in our solar system, moves in an orbit around the Sun. Similarly, the Moon moves in an orbit around the Earth. verb To move in an orbit around another object.
Saint Elmo’s fire
noun
A faint glow that is sometimes seen around airplane wings or tall, sharply pointed structures, such as ship masts or church spires, during a storm. The corona, or glow, is caused by the extreme buildup of electricity during the storm. It is often accompanied by hissing or crackling sounds. Many sailors used to think that Saint Elmo’s fire was a symbol of Saint Erasmus, their patron saint.
Cancer [The Crab] Cancer is the faintest and hardest-to-see zodiac constellation. It represents a crab that attacked the ancient hero Hercules when he was fighting the many-headed monster Hydra (Hercules crushed the crab underfoot). The constellation was known to the ancient Greeks as the Gates of Men, the doors through which souls came to enter the bodies of newborn infants. The ancient Egyptians called it the Power of Darkness, and associated it with Anubis, the jackalheaded god who weighed the hearts of the recently dead. Cancer gives its name to the northern tropic, which is the latitude at which the Sun is overhead on or around June 21. In the Northern Hemisphere, this is the longest day of the year and is also called the summer solstice. The Sun is in Cancer from late July to mid-August.
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LYNX The Beehive (M44) Also called Praesepe, this cluster of over 1,000 stars was known to the ancient Chinese as the Gas from Piled-up Corpses. It is about 577 light-years from us.
Ca
CANCER
LEO
Pollux
Altarf This orange giant star is about 300 light-years away and is the brightest star in Cancer. Its name means “the eye of the lion.” M44
M67 cluster Another star cluster, M67 is more closely packed than the Beehive and is about four times further away.
ECL
IPTI
C
Regulus
M67
With an estimate age of
CANIS MINOR
Altarf
years, M67 is one of the oldest
open clusters in our galaxy
P cancer
The symbol for Cancer is a crab.
SEXTANS
So you’re a Cancer? Find out what Cancers are like. Aries
Taurus
Gemini
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Giant star video
[] Cancer
Cancer gallery Leo
Virgo
Libra
Scorpius
Crab 90° N to 60° S February to May, after sunset 31 Altarf, Asellus Australis, Acubens, Asellus Borealis, Tegmine, Nahn, Kwan Kei M44, M67
HYDRA
Sagittarius
Capricornus
Aquarius
MONOCE
Pisces
Cancer gallery
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This is an artist’s impression of the view of a young planetary system from a nearby part of the Universe. From this angle you would be able to see the Beehive cluster in the background.
Constellations hardly seem to move over a span of 1,000 years, but comets such as this one pass through them in a few days. C/2001 Q4 (NEAT) passed through Cancer in May 2004.
The Beehive is one of the open star clusters closest to Earth, about 577 light-years away. It is one of the few clusters identified by the ancient Greeks. Most of its more than 1,000 stars are small, dim red dwarfs, the most common stars in the Universe.
This is a closer view of C/2001 Q4 (NEAT), with the Beehive cluster behind it. The blueness of the comet’s gas tail and the whiteness of its dust tail are now visible.
June 21–July 22 Feelings run deep for those born under the sign of the crab. Cancers can be moody and changeable, but they are always fiercely protective of the ones they love. They are imaginative, creative, and careful.
Security
Career
Home and family are top priorities for Cancers. They like to play it safe, and they will retreat into their shells at the first hint of discomfort or danger.
Cancers are great at bringing others out of their shells. They do well with jobs in human resources and training, and they may also be drawn to the medical field.
Friends
Sports
Famous Cancers:
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Nelson Mandela July 18
Tom Cruise
Selena Gomez
Meryl Streep
July 22
June 22
July 3
Naturally shy and retiring, Cancers are slow to make friends. They are fiercely loyal but don’t react well to criticism, and they can lash out if they feel attacked.
Cancers make good team players, because they consider their teams to be family. This sign loves water sports such as swimming, and they enjoy relaxing near water.
Hidden depths
The past
Cancers are hard to get to know. They hide their soft, sensitive interiors behind outer shells that can seem uncaring. They may appear more confident than they actually feel.
Sentimental by nature, Cancers cling to the past. Mementos and letters are prize possessions. When times change, they can find it hard to let go.
Giant star There are two main kinds of giant star: main-sequence stars with a diameter of 5 to 50 times that of our Sun, and stars that increase in size toward the ends of their lives. Of the main-sequence stars, blue giants are the hottest. They have surface temperatures of around 54,000°F (30,000°C) and shine incredibly brightly. Alcyone in the constellation Taurus is a blue giant. Orange giants, such as Altarf in the constellation Cancer, have a surface temperature of around 7,200°F (4,000°C), slightly cooler than the Sun. As a star nears the end of its life, it starts to run out of fuel at its core. It keeps on shining by burning hydrogen in shells around the core. This causes it to brighten and swell in size. As it expands, its surface cools and starts to glow red. The star is now known as a red giant. This image shows the remains of a giant star that exploded.
The red giant Aldebaran
in the constellation Taurus is
times brighter
than the Sun
latitude
noun
Any one of the many imaginary lines drawn around Earth from east to west that lie above or below the Equator. Each line, or latitude, marks a fixed distance from, and runs parallel to, the Equator. The Equator circles Earth halfway between the North and South Poles and is the longest line of latitude. It divides Earth into the Northern Hemisphere and the Southern Hemisphere. If you are standing on the Equator, your latitude is zero. If you are close to the North Pole, your latitude is nearly 90 degrees north. If you are close to the South Pole, your latitude is nearly 90 degrees south.
light-year
noun
A unit equal to the distance that light can travel in one Earth year in empty space. A light-year is equivalent to approximately 5.9 trillion miles (9.5 trillion km).
Tropic of Cancer
noun
The imaginary line that marks the northernmost edge of the tropics (very hot, damp regions of Earth, found near the Equator) and the northernmost latitude reached by the overhead Sun. It is 23.5 degrees north of the Equator and runs through Mexico, the Bahamas, Egypt, Saudi Arabia, India, and southern China. At the Tropic of Cancer, the Sun is directly overhead at noon on about June 21—the beginning of summer in the Northern Hemisphere and the beginning of winter in the Southern Hemisphere.
Leo[The Lion]
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Leo, the Lion, is one of the few constellations that looks anything like the animal it is supposed to represent. This lion was slain by the mythical hero Hercules. It is a fairly easy constellation to find, with many bright stars. We look to Leo to glimpse the Leonid meteor shower, which is visible around November 17. It is a very variable meteor shower, often with only a handful of meteors per hour, but occasionally as many as 30 per second can be seen. One of the stars in Leo, Wolf 359, is the third closest to the Sun, but since it is a dim red dwarf, it is too faint to see with the naked eye. The Sun passes through Leo from mid-August to mid-September.
LYNX LEO MINOR
URSA MAJOR Algieba Known as the lion’s forehead, Algieba is a double star composed of two yellow giants. The larger star has at least one planet.
THE SICKLE
LEO
Regulus The brightest star in the constellation is called Regulus, which means “little king.”
Denebola
Algieba
NGC 2903
M65
M66
M96
IC
IPT
M105
Regulus
ECL
M95
R Leonis
A planet orbiting the star
A variable star, distant (about 370 light-years away) but very bright, R Leonis goes through a series of changes in brightness and color over a 315-day cycle.
HYDRA
SEXTANS NGC 3521
VIRGO CRATER
has a mass about
LEO Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
22 times the mass of Earth
The symbol for Leo is a lion.
CORVUS
So you’re a Leo? Find out what Leos are like. Aries
Taurus
Gemini
Leo gallery Cancer
[ ] Leo
Virgo
Libra
Scorpius
Sagittarius
Lion 90° N to 65° S February to June, after sunset 12 Regulus, Algieba, Denebola, Zosma, Ras Elased, Chort, Al Jabhah, Subra M65, M66, M95, M96, M105, NGC 2903 NGC 3370, NGC 3521, NGC 3628
Capricornus
Aquarius
Pisces
Leo gallery
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The Leo Triplet consists of three galaxies: NGC 3628 (left), M65 (top right), and M66 (bottom right). All three are spiral galaxies.
M66 is a large galaxy that, like our own galaxy, has spiral arms bright with stars, with dark dust lanes running between them. M66’s shape was distorted when, billions of years ago, it collided with another galaxy, its now close neighbor NGC 3628.
NGC 3370, the Silverado galaxy, is similar in structure and size to our own galaxy: It is spiral, has a comparable mass, and (like the Milky Way) is about 100,000 light-years across.
NGC 2903 is a galaxy about 30 million light-years from Earth. It is called a barred spiral galaxy because it contains a central bar of stars. Around two-thirds of all spiral galaxies are barred.
Regulus (Alpha Leonis) is actually two pairs of stars. Three are stars of average size and brightness, like the Sun, while the fourth is a tiny, highly dense white dwarf.
M65 is a spiral galaxy that has undergone an unusual burst of star formation, probably due to a collision with one or both of its neighbors in the distant past.
July 23–August 22 Like the lion, Leos can think of themselves as the kings of the zodiac! They adore attention, so many Leos are natural leaders. Or they end up on the stage—many actors and actresses are Leos!
Performing
Friends
Theater, stand-up comedy, politics, and other activities that involve being onstage or having an audience all appeal to Leos.
Leos are sociable and make loyal friends. They will defend and stick by their pals through thick and thin.
Studying
Fine details
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Famous Leos:
Alfred Hitchcock August 13
Henry Ford July 30
Madonna August 16
Jennifer Lopez July 24
Hardworking and intelligent, Leos can be good in business. They definitely prefer being the boss to working in junior positions.
Leos love to know every little detail of what’s happening around them, and they will read every line of a contract (as everyone should!) so that they don’t miss anything.
Fashion
Ego
Because they like to stand out, Leos are often the first to wear the latest fashions or pick the most outlandish styles!
Leos can have big egos, so celebrity Leos have to try not to let their fame go to their heads!
Meteor shower Meteors, or shooting stars, are pieces of space debris that burn up as they pass through Earth’s atmosphere. On any given night, dozens of small meteors shoot across the sky. When 15 or more meteors per hour appear to come from the same point in space, they are called a meteor shower.
A meteor shower occurs when Earth passes through the path of a comet. Bits of comet debris create streaks of light in the night sky as they burn up in Earth’s atmosphere. There are certain points in Earth’s orbit of the Sun at which the planet passes through greater than normal amounts of debris. This means that some meteor showers occur at the same time each year. Meteor showers are often named after the constellation that they appear to come from. So Perseids seem to originate in the constellation Perseus, and Leonids seem to originate in the constellation Leo. Within the zodiac, Virginids appear from the direction of Virgo around March 20, Taurids appear from Taurus around November 4, and Geminids come from Gemini around December 14. The Leonid meteor shower is normally visible around November 17. Sometimes the displays can be really spectacular. During the Leonid showers of 1833, 1867, and 1966, a single observer could see over 10,000 meteors in just one hour.
Leonids enter Earth’s atmosphere at
This long-exposure photograph of the night sky was taken during a Leonid meteor shower.
per second
Red dwarf A red dwarf is a type of star, with a mass between 8 and 50 percent that of our Sun. Red dwarfs are dim and red because they are relatively small and cool. A typical red dwarf has a surface temperature of about 5,400°F (3,000°C). That may seem very hot, but for a star it is quite cool. It also means that red dwarfs last a long time, maybe as long as 1 trillion years, compared to around 10 billion years for a star like the Sun. Red dwarfs are by far the most common stars in our galaxy. The best-known red dwarf is Proxima Centauri, a tiny companion star to Alpha Centauri— the brightest star in the constellation Centaurus. Proxima Centauri is about the same distance from Earth as Alpha Centauri is, but because it is so dim, it can be seen only through a telescope. In fact, no red dwarfs can be viewed from Earth by the naked eye. This is an artist’s impression of a red dwarf.
the number of years
that a red dwarf star may last
planet
noun
A ball-shaped body in space that moves in orbit around a star such as the Sun. A planet has no light of its own—it reflects the light of the star that it is orbiting. There are eight primary planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
variable star
noun
A star that varies in brightness, color, or magnetic field strength. There are two types of variable star: eclipsing variables and physical variables. An eclipsing variable is a binary star whose brightness changes when one of its orbiting components passes in front of the other, blocking some of the stars’ combined light from reaching Earth. Physical variables are single stars that change in brightness, for various reasons; for example, they may expand and contract.
BOREALIS
Virgo [The Virgin]
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Virgo, the virgin, is the largest of the zodiac constellations. The Sun takes more than a month to pass through it, from the middle of September until early November. According to ancient Greek mythology, Virgo represents the goddess of justice; her scales of justice are represented by the nearby constellation Libra. Many other early stargazers also identified the constellation as a woman, often with an ear of corn in her hand to show her connection to fertility and growth.
Arcturus M87 galaxy This galaxy is 53 million light-years away. Unlike our own spiralshaped Milky Way, the M87 galaxy is roughly spherical in shape.
Porrima
Galaxies are bound together by gravity into clusters, or groups. Virgo contains the enormous and distant Virgo cluster, which is over 50 million light-years away and contains at least 3,000 member galaxies.
COMA BERENICES
VIRGO
SERPENS CAPUT
TIC
E
Spica
M104
CRA
CORVUS LIBRA HYDRA
Virgo
Virgo gallery Leo
[ ] Virgo
CENTAURUS
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Virgo is the virgin.
Cancer
3C 273
IP CL
Spica
—a large fraction of the known universe
Gemini
M61
Porrima
A bright double star, one of whose components is itself a double, Porrima lies about 39 light-years from Earth.
shines across 3 billion light-years
Taurus
M60
LEO
M86 M87 M58 M59 M49
The quasar
Aries
M89
BOOTES
The brightest star in Virgo, and the 15th brightest in the night sky, Spica is a blue giant.
So you’re a Virgo? Find out what Virgos are like.
M84
M90
Libra
Scorpius
Virgin 80° N to 80° S May, after sunset 2 Spica, Porrima, Vindemiatrix, Heze, Auva, Zavijava, Syrma M49, M58, M59, M60, M61, M84, M86, M87, M89, M90, M104
Sagittarius
Capricornus
Aquarius
Pisces
Virgo gallery
In this image, the faint green dots are asteroids a few hundred million miles from Earth. The four galaxies, all members of the Virgo cluster, are a trillion trillion times more distant.
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M84 is a lenticular (armless spiral) galaxy in the Virgo cluster. Scientists believe that there is a supermassive black hole in this galaxy’s nucleus.
This galaxy, IC 3418, has a star-filled tail, formed when the galaxy passed through a gas cloud in the Virgo cluster.
M104, the Sombrero galaxy, is an unusual spiral galaxy, with a bright central area far larger than normal and a thick, dark ring of dust around it. It is 28 million light-years from Earth.
An enormous jet of subatomic matter, powered by a black hole, emerges from the M87 galaxy. This galaxy is a strong source of radio waves and X-rays.
Famous Virgos:
August 23–September 22 Virgos are known for being serious, thoughtful, and focused. They like to take a step back and analyze a situation thoroughly before making a decision. Their great powers of detection make them particularly good at solving mysteries.
Friends
Fine details
You won’t find a better friend than a Virgo. Gentle and sympathetic, Virgos love taking care of others and are always willing to help out.
With an eye for detail, Virgos take great pains to follow through on everything they start. Having high standards helps Virgos get excellent results.
Pickiness
Health
Virgos worry a lot, since they tend to be hard on themselves— perhaps too hard! They can be quick to point out other people’s faults, too.
Virgos are neat and healthy, and they like everything around them to be tidy and well organized, too. They look after themselves and don’t eat a lot of junk food.
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Michael Jackson August 29
Roald Dahl September 13
Shyness
Outdoors
Beyoncé Knowles September 4
Virgos don’t express themselves easily, and they prefer to be in a supporting role rather than in the limelight. They can find it hard to be assertive or ask others for help.
Virgos love nature and outdoor activities. They like animals, and they play outdoor sports to stay fit and healthy rather than to win.
Quasar A quasi-stellar object—quasar for short— is an object in space that looks starlike from Earth but is actually much brighter than an ordinary star. In fact, a quasar is so bright that it can be seen from Earth even if it lies billions of light-years away, at the very edge of the visible Universe.
Astronomers believe that a quasar is a giant black hole in the center of a galaxy, surrounded by stars. These stars spiral inward toward the black hole, drawn by its force of gravity. As each star approaches the black hole, its gaseous body is torn apart by powerful gravitational forces and it emits a great burst of energy. This is the bright light that is visible from Earth.
These two quasars are located about 4.6 billion light-years from Earth.
Some quasars are times brighter than the Sun
Virgo cluster The Virgo cluster is the group of galaxies nearest to the Milky Way. It takes up a patch of sky in the constellation Virgo. Within this cluster, there may be as many as 3,000 member galaxies, held together by gravity. There are many types of galaxy in the Virgo cluster, including spiral, eliptical, and irregular galaxies. One of the largest members of the cluster is the giant elliptical galaxy M87, which is a powerful source of infrared radiation, radio waves, and X-rays. The Virgo cluster lies within an even larger structure: the Virgo supercluster, which is thought to have more than 1 million member galaxies.
This image shows several galaxies of the Virgo cluster.
the diameter of the
Virgo cluster, in light-years
galaxy
noun
A huge group of stars, planets, gas, and dust, held loosely together by gravity. Galaxies are present throughout the known Universe; they vary in size from dwarfs that contain 10 million stars to giants of over 100 trillion stars. Galaxies are usually in the shape of a spiral, an elliptical ball, or an irregular cloud. Everything in a galaxy moves around a center. Our own galaxy is called the Milky Way.
gravity
noun
The force that pulls things toward massive objects such as planets and stars. The strength of the force of gravity between objects depends on two things: the mass of the objects and the distance between them. Gravity is the force that pulls things toward the center of Earth and keeps them from floating away. It makes objects fall and gives them weight. It keeps the Moon in orbit around Earth, it keeps the planets in orbit around the Sun, and it pulls stars into galaxies. Gravity is universal.
BOOTES
Libra [The Scales] Libra, the Scales, is a dim constellation and the only one in the zodiac that does not represent a living creature. This is true as of the first century bce, when the ancient Romans changed its name from Claws of the Scorpion to Libra. This means that Libra is the newest sign of the zodiac. In China, the constellation was originally thought of as a crocodile or dragon, but it later became the scales there as well. According to some historians, the annual regulation of merchants’ weights (a process that would have required the use of accurate scales) took place in China when the Sun entered Libra. The Sun is in Libra from late October until late November.
SERPENS CAPUT
Zubeneschamali Also known as Beta Librae, Zubeneschamali is the brightest star in Libra. It has an unusual greenish glow.
VIRGO Zubeneschamali
LIBRA 48 Librae All stars spin, but 48 Librae is exceptional: It rotates so rapidly that rings of gas are frequently flung off it into space.
PTIC
ECLI
Zubenelakribi
The Latin word
HOME
Zubenelgenubi
NGC 5897
This is an eclipsing binary star—its light appears dimmer if one component star is passing between Earth and the other star.
HYDRA
Antares
gives us the abbreviation
lb for “pound”
SCORPIUS
LUPUS
CENTAURUS
Libra Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Libra is scales.
So you’re a Libra? Find out what Libras are like. Aries
Taurus
Gemini
Cancer
Libra gallery Leo
Virgo
[ ] Libra
Scorpius
ARA
Scales 65° N to 90° S June, after sunset 29 Zubenelgenubi, Zubeneschamali, Zubenelakrab, Zubenelakribi, Brachium, 48 Librae Gliese 581
Sagittarius
Capricornus
Aquarius
Pisces
Libra gallery
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Gliese 581 itself (center) is a much cooler and dimmer star than the Sun. This means that to support life, any Earth-like worlds would need to be much closer to it than Earth is to our Sun.
Of the hundreds of planets known to orbit other stars, very few are thought to be capable of supporting life. Yet Gliese 581, a red dwarf star just 20 light-years from Earth in the constellation Libra, has at least six planets, two of which may be habitable. This is an artist’s impression of how one of these habitable planets might appear, with Gliese 581 in the distance.
This shows our Moon, with the Libran star Zubenelgenubi and a companion star in the distance. The Moon looks red because this photograph was taken during a lunar eclipse.
Famous Libras:
September 23–October 22 Libra is symbolized by a pair of scales; fittingly, Libras have a natural sense of justice. They like to weigh things carefully, and they come across as cool, calm, and collected. Their ability to see both sides of every argument can make them indecisive, though.
Popularity
Pampering
Libras tend to be very popular. Sympathetic and good at listening, they are experts at both making and keeping friends.
Libras love to treat themselves and are not very good at self-denial. A Libra can never get enough candy or ice cream!
Peace
Fashion
Libras are natural peacemakers. They like to solve problems and resolve arguments. Since they dislike conflict, they want everyone to get along.
Blessed with great taste, Libras have no problems picking out clothes that they will look good in. They are always chic and up to date.
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Bruce Springsteen September 23
Eleanor Roosevelt October 11
Career
Friends
Mahatma Gandhi October 2
With their built-in sense of justice, Libras make great lawyers and judges. Diplomatic and tactful, they can rise to top positions if they enter politics.
Libras are very sociable. They love the company of others and hate spending time alone. Luckily, their natural charm means that they are rarely alone for long.
Sun
noun
The star at the center of our solar system. All of the planets in the solar system revolve around the Sun. Like the other stars in the night sky, the Sun is a huge ball of extremely hot gases that shines with its own light and gives off its own heat. Its light and heat sustain all life on Earth. The Sun was formed with the rest of the solar system about 4.5 billion years ago; it is expected to last another 5 billion years in its current state. Its core temperature is about 28,800,000°F (16,000,000°C).
Scorpius [The Scorpion] Behind the stars of Scorpius lies a dense part of the Milky Way that contains a wide range of astronomical objects, including many star clusters. Remarkably, the constellation’s bright stars do form the shape of a scorpion. According to legend, this is the scorpion that killed the hunter Orion—and the constellation Orion does indeed leave the sky just as Scorpius is rising, as if in retreat. Scorpius was once a far larger constellation, because Libra used to be included in it; the stars used for Libra were part of the Scorpion’s claws. In ancient China, the bright stars of Scorpius formed part of the constellation of the Azure (blue) dragon. The Sun is in Scorpius from late November to mid-December.
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SERPENS CAPUT
Xi Scorpii A multiple star with five components, Xi Scorpii is about 90 light-years away.
Antares
Xi Scorpii
SERPENS CAUDA
This star is known as the rival of Mars, because both it and the planet have a reddish tinge. It is a variable supergiant star with a period around five years; it is about 900 times the Sun’s diameter.
OPHIUCHUS ECLIPTIC M80
Antares
M7 cluster This bright cluster of stars is visible with the naked eye; its brightest stars look as if they are connected in lines. It is about 800 lightyears away.
The star Antares is
LUPUS
NGC 6383
Shaula
NGC 6231
times larger than
SCORPIUS
M6
M7
LIBRA
M4
A large, bright cluster of about 120 stars, NGC 6231 is visible with the naked eye and is about 6,000 light-years from us.
NGC 6322
our Sun
NGC 6388
NGC 6124
NGC 6231 NGC 6178
NORMA
ARA TELESCOPIUM Scorpius Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Scorpius is a scorpion.
So you’re a Scorpio? Find out what Scorpios are like. Aries
Taurus
Gemini
Cancer
Scorpius gallery Leo
Virgo
Libra
[ ] Scorpius
Sagittarius
Scorpion 40° N to 90° S April to September, after sunset 33 Antares, Shaula, Sargas, Dschubba, Wei, Girtab, Acrab, Lesath, Alniyat, Iclil, Jabbah, Xi Scorpii M4, M6, M7, M63, M80, NGC 6231, NGC 6383
CIRCINUS
Capricornus
Aquarius
Pisces
Scorpius gallery
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When globular clusters were first studied in the 18th century, they were thought to be featureless, cloudy structures. M4 was the first to reveal that they are all made of closely packed stars.
Fewer than 100 light-years across and containing several hundred thousand stars, M80 may be the most densely star-filled globular cluster in our galaxy.
Jabbah, or Nu Scorpii, is a close association of at least five and perhaps as many as seven stars. This large area of the sky (about 60 times the size of the Full Moon) is shown in infrared light, revealing the twists and veils of dust clouds.
Until the 18th century, astronomers recorded few clusters, but the bright and easily found M7 is an exception: It was first mentioned as long ago as 130 ce.
Famous Scorpios:
October 23–November 21 A Scorpio has hidden depths—beneath a cool, calm exterior beats a passionate heart. Scorpios may not say much, but there’s a lot going on under the surface. Determined and capable, they can transform their lives and the lives of others.
Secrets
Leadership
Scorpios are deeply private people. They keep to themselves and rarely give up their secrets. Sometimes it’s hard to know exactly what a Scorpio is thinking.
Determined, smart, and resourceful, Scorpios make great leaders. They notice what is going on around them and take time to support their staff.
High energy
Intellect
Christopher Columbus October 31
Pablo Picasso
Scorpios are intense and driven. Whatever they are interested in—whether it’s sports, music, or science—they give it their all.
Scorpios have sharp brains. They use their powers of reason to get to the heart of any matter. They won’t rest until they get the truth, so they make good detectives.
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October 25
Hillary Clinton October 26
Criticism
Trust
The sting in the tail of a Scorpio is his or her blistering tongue, which can sometimes lash out. Scorpios make tough enemies when they think it’s necessary.
Trust doesn’t always come easily to Scorpios. They need their friends to be loyal. Scorpios make deep, long-lasting friendships.
Antares The bright red star Antares, also known as Alpha Scorpii, is in the constellation Scorpius in the Milky Way galaxy. It is a cool, low-density supergiant, with a radius 800 times that of our Sun. To put this in perspective, if Antares was placed in the Sun’s position in space, its surface would extend well past the orbit of Mars! Antares is cooler than many other stars. Its surface temperature of about 5,800°F (3,200°C) is only slightly more than half the temperature of the Sun. But because Antares is so large, with a vast surface area from which light can escape, it shines very brightly in the night sky. Like all red giants and supergiants, Antares is coming to the end of its life. When it runs out of fuel, it will collapse under its own weight, triggering an enormous supernova explosion and resulting in either a tiny neutron star or a black hole. Luckily, Earth is far enough away from Antares for this event to be of no danger to us. Antares has a small greenish companion, Antares B, which is visible only through a telescope.
The red supergiant star Antares is surrounded by yellow glowing dust.
the number
of times brighter
than our Sun Antares is
Supergiant star Supergiants, the brightest known stars, generally have absolute brightnesses 10,000 times that of the Sun. The brightest supergiants are sometimes known as hypergiants. Supergiants are stars with masses typically ranging from 10 to 100 times the mass of the Sun, and radii from 20 to 1,000 times the radius of the Sun. Because of their enormous size, supergiants have relatively short life spans. There are different colored supergiants, from blue (extremely hot) to red (relatively cool). Several stars familiar to the naked eye are supergiants, including Antares (Alpha Scorpii), Betelgeuse (Alpha Orionis), Canopus (Alpha Carinae), Deneb (Alpha Cygni), and Rigel (Beta Orionis).
The Tarantula Nebula has a cluster of bright blue supergiant stars at its heart.
(30,000–50,000°C):
the surface temperature
of a blue supergiant
Milky Way The galaxy that includes our Sun, the Earth, and the rest of its solar system, along with billions of stars, gas and dust clouds, and other objects, is called the Milky Way. The solar system is just one very tiny part of the Milky Way galaxy, which in turn is just one very tiny part of a Universe that contains billions of galaxies. The nighttime summer sky shows the edge of the Milky Way galaxy as a band of faint light arching across the sky from horizon to horizon—the combined light of millions of stars. This band is broadest and brightest in the constellation Sagittarius, and thinner and fainter in the constellation Cygnus. Ancient people saw the band of light as a river of milk or a road joining the Earth with the heavens.
A laser beams from the fourth telescope of the European Southern Observatory’s Very Large Telescope (VLT) directly at the center of the Milky Way.
The total mass of the Milky Way is about the mass of the Sun
Seen edge on from space, the Milky Way galaxy is shaped like a gigantic disk with a bulge at its center, with most of its stars, gas, and dust near its central plane. The central nucleus of the galaxy, which lies in the direction of Sagittarius, is about 10,000 light-years thick. The disk flattens toward its edge: In the vicinity of the Sun, it is about 3,000 light-years thick.
multiple star
noun
A system of two or more stars that appear to the naked eye as a single star. The star Castor in the constellation Gemini is actually made up of six stars—three binary systems orbiting one another. However, if you look at Castor without a telescope, it appears to be a single star.
Sagittarius [The Archer] Sagittarius is one of the night sky’s two centaurs—a creature from ancient Greek mythology with the upper body of a man and the lower body of a horse (the other is Centaurus). It is one of the oldest identified constellations, though what it represents has varied from a herdsman to a swan, a horse, or a tiger. Our galaxy, the Milky Way, passes through Sagittarius. In fact, the center of the Milky Way, where the galaxy is brightest, lies within the constellation. Sagittarius contains star clusters and many nebulae, which are cloudlike masses of dust or gas, some glowing and some dark. The Sun is in Sagittarius from the middle of December until the middle of January.
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AQUARIUS AQUILA
Trifid Nebula (M20) Named after the triple lanes of cosmic dust that lie across it, this is actually a pair of side-byside nebulae.
SERPENS CAUDA
SCUTUM NGC 6818 NGC 6822
Lagoon Nebula (M8)
M17 M18
NGC 6716
This emission nebula has a dark lane down its center, composed of clouds of sooty dust.
M24
M25 M75
M21
ECLIPT
IC
M20 M28
M22
Kaus Australis
Nunki
The brightest star in the constellation is Kaus Australis, which means “the southern part of the archer’s bow.”
M23
M8
THE TEAPOT M55
M54
SAGITTARIUS NGC 6723
Scientists think that the radio wave source
Rukbat
M69
M70
Kaus Australis
CORONA AUSTRALIS
Arkab
is the location of a superhuge
TELESCOPIUM
black hole at the center of the Milky Way
ARA
sagittarius
The symbol for Sagittarius is an archer.
So you’re a Sagittarian? Find out what Sagittarians are like. Aries
Taurus
Gemini
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Black hole video
Cancer
Sagittarius gallery
PAVO
Leo
Virgo
Libra
Scorpius
Archer 55° N to 90° S August, after sunset 15 Kaus Australis, Nunki, Ascella, Kaus Media, Kaus Borealis, Rukbat, Arkab M8, M17, M18, M20, M21, M22, M23, M24, M25, M28, M55, NGC 6559
[ ] Sagittarius
Capricornus
Aquarius
Pisces
Sagittarius gallery
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In M8, the Lagoon Nebula, both the collapsing clouds that occur before star formation and the clouds of matter thrown off by newborn stars indicate that this is the birthplace of many stars.
M25 is an open cluster about 2,000 light-years from Earth. It contains a Cepheid variable, a type of star used by astronomers to gauge the distances of objects in the local Universe.
M17, the Omega (or Swan) Nebula, is a thin mass of glowing gas that stretches through over 40 light-years of space. The intense radiation from an embedded cluster of hot young stars provides the power for this interstellar light show.
NGC 6559’s glow is due to the heating of hydrogen gas by newly formed stars; the dark areas are clouds of sooty dust, produced by ancient stars.
November 22–December 21
Famous Sagittarians:
Sagittarius, the archer, is the extrovert of the zodiac. Sagittarians are almost always optimistic, enthusiastic, and sunny. They’re bundles of energy who love to travel. Because they tend to be restless, they may be impatient and are easily bored.
Debate
Adventure
Sagittarians find it easy to express their ideas and don’t mind a good argument. They can summarize other people’s views and are good at moderating debates.
Sagittarians are thrill seekers who are always on the lookout for adventure. They love outdoor sports and activities, and they are good with horses and dogs.
Travel
Honesty
Sagittarians have journeys to take. They adore travel and are the sign most likely to settle in foreign countries—at least for a while, until they get the urge to move again.
Sagittarians love to speak their minds and can be tactless. They are extremely honest, and they don’t always think before they speak, which can offend others.
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Walt Disney December 5
Britney Spears December 2
Jay-Z December 4
Freedom
Differences
Sagittarians value their freedom. They hate routine and will soon get restless if they feel trapped. Sagittarians hate to be tied down.
Curious and open minded, Sagittarians are attracted to people who stand out from the crowd. They often choose friends with backgrounds different from their own.
Black hole A black hole is a region in space with very strong gravity. Not even light can escape its pull. This means that black holes are invisible to the naked eye. A black hole is formed when an enormous star collapses at the end of its life. There are huge forces at play within a star: The immense inward pull of gravity from the star’s core is counterbalanced by the tremendous outward push of heat energy that is produced as atoms collide and fuse at the core. However, when the star runs out of fuel, it starts to cool and contract. Smaller stars, the size of our Sun, collapse to form objects called white dwarfs. Larger stars collapse into neutron stars. But massive stars collapse completely, becoming even smaller and denser than neutron stars. They have gravitational fields so strong that even light cannot escape them. These collapsed stars become black holes. No black hole has ever been photographed, but astronomers think that one may look like this.
the distance from the nearest black hole to Earth
Cosmic dust Cosmic dust (also known as stardust or space dust) is made up of various elements—such as carbon, oxygen, and iron—that have combined to form small particles of solid material floating around in space. Cosmic dust is made in stars, then blown off by a slow wind or a huge star explosion. Some of the dust is then recycled: It is drawn into giant swirling clouds of gas and dust, called nebulae, where some of it is consumed as the next generation of stars is born. Particles of cosmic dust can also stick together to form clusters, which in turn stick together to form rocks. Gravity pulls the rocks together, and they can eventually become planets.
Cosmic dust and gases mix together in the Fox Fur Nebula.
the amount of cosmic dust that falls to Earth each year
emission nebula
noun
A vast cloud of dust and gases that contains hot stars that make it glow, sometimes very brightly. In photographs, these nebulae often look red because they are very rich in hydrogen, which gives off red light when it is energized. The Great Nebula in the constellation Orion is an emission nebula. It can be seen by the naked eye, appearing as a fuzzy patch of light below the three stars in Orion’s belt. The Lagoon Nebula in the constellation Sagittarius is another emission nebula.
radio wave
noun
A type of energy that makes up part of the electromagnetic spectrum. These waves of energy have the longest wavelengths in the spectrum. They can be generated artificially: When you turn on a radio, it receives broadcast radio waves and converts them into sound. There are also natural sources of radio waves in space. Planets, comets, nebulae, stars, and galaxies can all emit radio waves. Astronomers have developed radio telescopes to study these sources.
Capricornus [The Sea Goat] Many ancient civilizations saw Capricornus as we do today—representing a creature that is half goat, half fish. Images of the constellation in this form date back as far as the 12th century bce. Despite its great age, Capricornus is not an impressive constellation—it is small, dim, and hard to find. But it was important to the ancient Greeks, who called it the Gate of the Gods and regarded it as the portal through which souls traveled from Earth to heaven. The latitude at which the Sun is overhead on or around December 21 is called the Tropic of Capricorn. In the Northern Hemisphere, this is the shortest day of the year, called the winter solstice. The Sun is in Capricornus from late January until mid-February.
The planet
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EQUULEUS
Algiedi Some stars look close together only because they happen to lie in the same direction from Earth. Algiedi, or Alpha Capricorni, is one of these optical doubles.
AQUILA
AQUARIUS Algiedi
Dabih Also known as Beta Capricorni, this true binary star is about 340 light-years from us.
Dabih ECL
M30 cluster This cluster of stars has a densely packed core, with thin extensions that can look eerily handlike in some viewing conditions.
IPTI
C
CAPRICORNUS
M30
PISCIS AUSTRINUS MICROSCOPIUM Fomalhaut
was in Capricornus when
SAGITTARIUS
it was first discovered in 1846
capricornus
GRUS
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Capricornus is a sea goat.
So you’re a Capricorn? Find out what Capricorn are like. Aries
Taurus
Gemini
Cancer
Capricornus gallery Leo
Virgo
Libra
Scorpius
Sea goat 60° N to 90° S September, after sunset 40 Algiedi, Dabih, Nashira, Deneb M30, NGC 6907
Sagittarius
[ ] Capricornus
Aquarius
Pisces
Capricornus gallery
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M30 is a globular cluster about 30,000 light-years away. Its core has collapsed, making it one of the densest regions in the galaxy.
Algiedi (from the Arabic word meaning “billy goat”) is a multiple star system. The bright pair of stars is called Prima Giedi, and the dimmer star at the upper right is Secunda Giedi. Prima and Secunda are very far apart but happen to lie in a similar direction, so they appear to be close to each other.
When viewed from farther away, M30’s compact shape is more obviously visible. It is possible that the cluster once belonged to another galaxy.
Famous Capricorns:
December 22–January 19 Considered the most serious sign of the zodiac, Capricorns are hard workers. They don’t mind jumping into tasks, because they are self-disciplined and careful. Capricorns put great effort into achieving their goals and almost always get results.
Feelings
In charge
Capricorns can find it difficult to express their feelings or form friendships. But a Capricorn friend is a friend for life—he or she won’t let you down.
A Capricorn likes to be the boss. Steady and responsible, they make good managers. But their quick and easy grasp of any subject can come across as arrogance.
Plans
Self-reliance
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Cautious by nature, Capricorns are good at planning. They think ahead to anticipate problems before they arise.
Capricorns are independent and naturally selfsufficient. Because they are good with their hands, they would do well if marooned on a desert island!
Martin Luther King, Jr. January 15
Stephen Hawking January 8
Endurance
Career
Betty White January 17
Capricorns are tough. When times are hard, they cope with whatever life throws at them. A goatlike stubbornness helps them accomplish their goals.
Working for the good of a community often motivates Capricorns. They make good teachers and social workers, and they can rise to high levels in their professions.
Tropic of Capricorn
noun
The imaginary line that marks the southernmost edge of the tropics (very hot, damp regions of Earth, found near the Equator) and the southernmost latitude reached by the overhead Sun. It is 23.5 degrees south of the Equator and runs through Australia, Chile, southern Brazil, and northern South Africa. At the Tropic of Capricorn, the Sun is directly overhead at noon on about December 21—the beginning of winter in the Northern Hemisphere and the beginning of summer in the Southern Hemisphere.
Aquarius [The Water Carrier] Aquarius is one of the oldest constellations, identified by the Babylonians as a man pouring water from a vessel. The ancient Greeks decided that the man was Ganymede, cupbearer to the gods on Mount Olympus. From the year 2597, Aquarius will contain the vernal equinox. This is the point at which the Sun crosses the ecliptic from south to north each year. The vernal equinox moves slowly through all of the constellations of the zodiac, taking about 26,000 years to complete one circuit. So the actual “Age of Aquarius,” when the vernal equinox occurs under this constellation, is not yet due to dawn for over five centuries. The Sun is in Aquarius from late February until early March.
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M2 (NGC 7089) This bright globular cluster, about 37,000 light-years from Earth, is easy to see with binoculars. But its stars are so densely packed that a good telescope is needed to distinguish them.
PEGASUS
EQUULEUS M2
PISCES
WATER JAR
Zeta Aquarii This is a binary star composed of two very similar stars, which complete an orbit around each other every 590 years.
ECL
AQUARIUS
IPT
IC
NGC 7009 M72 M73
Saturn Nebula NGC 7009, known as the Saturn Nebula because of its shape (similar to the planet’s), is a planetary nebula, a series of dust and gas shells rapidly expanding from the core of a dead star.
NGC 7293
CAPRICORNUS SCULPTOR PISCIS AUSTRINUS MICROSCOPIUM
Four extrasolar planets orbit the red dwarf star aquarius
PHOENIX
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
The symbol for Aquarius is a water carrier.
So you’re an Aquarian? Find out what Aquarians are like. Aries
Taurus
Gemini
Cancer
Aquarius gallery Leo
Virgo
Libra
Scorpius
Water carrier 65° N to 90° S October, after sunset 10 Beta Aquarii, Alpha Aquarii, Delta Aquarii, Zeta Aquarii M2, M72, M73, Saturn Nebula, Helix Nebula
Sagittarius
Capricornus
[ ] Aquarius
Pisces
Aquarius gallery
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The name M2 refers to this globular cluster’s status as the second entry in the catalog of nebulae written by the French astronomer Charles Messier, from 1774 onward. In 1783, the German-born British astronomer William Herschel discovered that it was actually composed of individual stars.
M72 is a globular cluster about 50,000 light-years from Earth. The redder stars are the cooler ones; blue stars are hot and often young.
Gliese 876 is a red dwarf, with at least four planets in orbit around it that are similar to the four outer planets of our own solar system.
The Helix Nebula is a dramatic example of a planetary nebula: Its central white dwarf is all that remains of a dead star whose outer layers have now expanded into the colorful globe of gas that extends far out into the space around it. The colors reveal the gases of the nebula— hot hydrogen is green, cool hydrogen is red, and hot oxygen is blue.
Famous Aquarians:
January 20–February 18 Aquarius, the water carrier, is a bit of a contradiction. On one hand, an Aquarian can be fun loving and outgoing; on the other hand, he or she can also have a quiet, aloof side. Aquarians are fiercely independent, and they don’t like clingy people!
Brains
Helpfulness
Original thinkers, Aquarians can see all sides of an argument. They relish a mental challenge and love the chance to use their brains. They definitely like to be right!
Aquarians enjoy helping others and are generous with their time. They are good at solving other people’s problems. They also need time to relax alone, though.
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Jennifer Aniston February 11
Oprah Winfrey January 29
World changers
Determination
Talent
Personality
Aquarians like to fight for a cause, whether it’s the environment, human rights, or equality issues. They are born politicians!
Aquarians are talented in many ways. They are both artistic and scientifically minded. They use their imaginations and can come up with ideas at lightning speed.
Jackie Robinson January 31
Once Aquarians set a goal for themselves, they will do everything they can to achieve it. They will use their energy to make their dreams come true.
Aquarians behave in different ways at different times. Sometimes they can be extroverted and enthusiastic, and at other times they can be shy and reserved.
Extrasolar planet Planet C Planet B
687: the number of extrasolar planets identified in November 2011
Star
An extrasolar planet is a planet that lies outside our solar system. For hundreds of years, astronomers have wondered whether there are other planets orbiting distant stars. But because planets have no light of their own and only reflect the light produced by the star they are orbiting, they are much harder to detect in space than stars are. In the last few decades, astronomers have found new ways of proving the existence of extrasolar planets. Using powerful telescopes, they look for “wobbles” in the motion of a star. These wobbles suggest that a large planet may be orbiting the star and dimming its light as the planet passes between the star and Earth. Like the planets in our solar system, extrasolar planets can be made of rock, liquid, or gas. They can orbit several different types of star or can float freely. There are also extrasolar planets that orbit brown dwarfs, which are celestial objects that shine less brightly than stars do. Some of the extrasolar planets that have been discovered recently may be able to support life. They lie in the habitable zones of stars—the regions of the Universe where liquid water may exist. One such planet is Gliese 581c.
Planet D
This image shows the star HR 8799 and its three known planets.
the number of
extrasolar planets
identified by December 2011
Globular cluster A globular cluster is a group of many thousands of stars. Through a telescope, a globular cluster appears full and round, like a stellar globe. Globular clusters have very little gas or dust between their stars. Astronomers believe that they are some of the oldest objects in the Milky Way—they could be 10 or 15 billion years old. There are many stars in globular clusters. The brightest are huge red giants. Globular clusters usually contain a few hundred red giant stars. But most of the stars are fainter and lighter than red giants. These are called Population II stars. A specific type of Population II star—called RR Lyrae stars—lives in globular clusters. Astronomers have found that their light pulsates regularly. RR Lyrae stars help astronomers measure the distances from Earth to their clusters. Most globular clusters are similar to one another. One interesting cluster is called Palomar 5, which is about 75,000 light-years from Earth. Astronomers photographed Palomar 5 as it was torn apart by the Milky Way’s gravitational forces. They are now studying the streams of stars left behind. This may help them learn about dark matter in our galaxy.
This image shows a globular cluster in the Milky Way.
More than
the number of globular clusters discovered in the Milky Way
ecliptic
noun
The path that the Sun appears to trace around the sky, or celestial sphere, each year. Twelve of the constellations around the ecliptic make up the zodiac. The Sun also passes through a thirteenth constellation, Ophiuchus.
equinox
noun
One of the two points of intersection between the ecliptic (the Sun’s apparent annual path) and the celestial equator (the equator of the celestial sphere); also, the two moments in each year when the Sun is exactly over the Equator, and day and night are therefore of equal length. In the Northern Hemisphere, the vernal, or spring, equinox occurs about March 21, and the autumnal equinox occurs about September 23. In the Southern Hemisphere, these dates are reversed.
Pisces [The Two Fish] This constellation has been regarded since ancient times as a pair of fish connected by knotted cords. However, the stars chosen to mark the fish have changed over the millennia, so now the fish are farther apart and swimming in different directions. Some legends refer to the fish as the offspring of the Southern Fish (Piscis Austrinus), a constellation close to Aquarius. Since Pisces contains the vernal equinox, the point at which the Sun moves from south to north of the ecliptic each year, it is currently the first sign of the zodiac. Early Chinese astronomers regarded the stars in what we call Pisces as part of a much larger constellation, the Dark Warrior. The Sun is in Pisces from mid-March until late April. Alpherg, the brightest
star in Pisces, is approximately
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LACERTA
ANDROMEDA
M74 galaxy This is a faint but beautiful spiral galaxy about 30 million lightyears from Earth.
PEGASUS ARIES M74
Circlet of Pisces This asterism is a circle of seven stars, including TX Piscium, a dark red irregular variable star.
PISCES EC
Alrescha Also known as Alpha Piscium, Alrescha represents the knot in the cord joining the two fish. It is actually a double star with a 900-year orbit.
CIRCLET
LIP
Alrescha
TIC
CETUS
AQUARIUS light-years from Earth
So you’re a Piscean? Find out what Pisceans are like. Taurus
Gemini
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Spiral galaxy video
The symbol for Pisces is two fish.
Aries
PISCES
Cancer
Pisces gallery Leo
Virgo
Libra
Scorpius
Two fish 90° N to 65° S November, after sunset 14 Alpherg, Simmah, Alrescha, Vernalis M74, NGC 470, NGC 474
Sagittarius
Capricornus
Aquarius
[ ] Pisces
Pisces gallery
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Arp 227 is a pair of unusual galaxies about 100 million lightyears from Earth. On the left is NGC 474, surrounded by shells of uncertain origin, and on the right is spiral galaxy NGC 470.
Comet Ikeya-Zhang passed through the inner solar system over three centuries ago, in 1661. It returned in 2002, when this photograph was taken.
M74, or NGC 628, is a spiral galaxy about 32 million light-years away from Earth. In 2002, a hypernova, an extremely rare astronomical event, was observed there. A hypernova is an immense explosion marking the destruction of a star more than 100 times the mass of the Sun.
At just 14 light-years away, Van Maanen’s Star is one of the closest white dwarfs to Earth. It is extremely dense—on Earth, a teaspoonful of its material would weigh several tons.
Famous Pisceans:
February 19–March 20 Those represented by Pisces, the fish sign, are sensitive souls who are ruled by their emotions. Their natural sympathy helps them maintain strong relationships. Loving and lovable, they find it easy to make friends, and they will stick with them no matter what.
Artists
Sensitivity
Pisceans may show their strong artistic streaks by writing poetry, painting, or making music. They can also be good actors or actresses.
Gentle and compassionate, Pisceans don’t like to be criticized. Harsh words can sometimes make them cry, as can the sight of cruelty.
Dreams
Career
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The visionaries of the zodiac, Pisceans are sometimes able to see into the future. They should trust their intuitions and analyze their dreams.
Taking care of others comes naturally to Pisceans, so they make excellent nurses and caretakers. They don’t usually enjoy being in charge.
Albert Einstein March 14
Mia Hamm March 17
Motivation
Impracticality
Queen Latifah March 18
Like their symbol, Pisceans can swim in both directions. Those motivated to swim upstream can achieve their dreams. But those drifting downstream can easily waste their talents.
Pisceans can sometimes be impractical. They aren’t always great with money, so they need to be careful that their spending doesn’t get out of control.
Asterism An asterism is a cluster of stars in the night sky that forms an easily recognized pattern. In general, asterisms are simple shapes, made up of a small number of stars. They are usually named after objects, symbols, or geometric shapes. The most famous asterism is the Big Dipper. It includes seven stars that form a ladle. The Big Dipper is part of the larger constellation Ursa Major, the Great Bear. Another easy-to-spot asterism is the Great Square of Pegasus, a square formed by the four brightest stars in Pegasus, the Winged Horse. There are several well-known asterisms within the constellations of the zodiac. The Teapot, in Sagittarius, is made up of the Archer’s bow and arrow; the Circlet of Pisces is the westernmost of the Two Fish; and the Sickle, in Leo, is the curve of stars at the front end of the Lion.
The Big Dipper is an asterism.
Spiral galaxy As the name suggests, a spiral galaxy looks like a spiral, with long arms winding toward a bright bulge at the center. The bulge is a huge, tightly packed group of mostly older stars that are being drawn toward a supermassive central black hole. The arms are made up of mostly younger stars, dust, and hot gas. Spiral galaxies are divided into three main types depending on how tightly their arms are wound. “Type a” spiral galaxies have very tightly wound arms, “type b” galaxies have moderately wound arms, and “type c” galaxies have very loosely wound arms. In addition, some spiral galaxies have bright bars running through them. They are known as barred spirals. Our own galaxy, the Milky Way, is a barred spiral galaxy. Both ordinary spiral galaxies and barred spirals rotate about their centers.
This image of the spiral galaxy M106 was taken “edge on” so that its central bulge is visible.
the estimated number of stars within the spiral galaxy the Milky Way
ecliptic
noun
The path that the Sun appears to trace around the sky, or celestial sphere, each year. Twelve of the constellations around the ecliptic make up the zodiac. The Sun also passes through a thirteenth constellation, Ophiuchus.
equinox
noun
One of the two points of intersection between the ecliptic (the Sun’s apparent annual path) and the celestial equator (the equator of the celestial sphere); also, the two moments in each year when the Sun is exactly over the Equator, and day and night are therefore of equal length. In the Northern Hemisphere, the vernal, or spring, equinox occurs about March 21, and the autumnal equinox occurs about September 23. In the Southern Hemisphere, these dates are reversed.
VULPECULA
Ophiuchus [The Serpent Holder]
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SAGITTA
Each December, the Sun passes through the constellation of Ophiuchus, the Serpent Holder. Although it is one of thirteen constellations to cross the ecliptic, Ophiuchus is not recognized as an official zodiac sign. The constellation represents an ancient Greek physician named Asclepius, whose snake-entwined staff remains a symbol of medicine today. In 1604, a supernova was seen in Ophiuchus. It was the last known supernova in our galaxy. Barnard’s Star is also in this constellation; it is the star with the greatest proper motion (that is, movement across the sky as compared to other stars’). Even so, Barnard’s Star’s movement is very slow—it takes nearly two centuries for it to cross the width of the Full Moon.
Rasalhague M10 and M12 M10 is a globular cluster of stars, about 14,000 light-years from Earth. M12—another globular cluster, about 4,000 light-years farther away—lies near it in our view of the sky.
NGC 6633 NGC 6572
The two almost equally bright stars in this binary system take 260 years to complete a single orbit.
SCUTUM SERPENS CAUDA SAGITTARIUS
ECLIPTIC
Antares
Symbol Visible at latitudes Best time to see Rank in constellation size Stars in decreasing order of brightness Other objects in constellation
Cancer
M9
M19
Ophiuchus
Gemini
M107
M27
second-closest star to Earth
Taurus
M12
OPHIUCHUS
Tau Ophiuchi
in Ophiuchus, is the
Aries
M10
M14
CAPRICORNUS
The symbol for Ophiuchus is a serpent holder.
SERPENS CAPUT
IC 4665
Leo
Serpent holder 80° N to 80° S July, after sunset 11 Rasalhague, Sabik, Zeta Ophiuchi, Yed Prior, Tau Ophiuchi, Barnard’s Star, RS Ophiuchi M9, M10, M12, M14, M19, M27, M62, M107, NGC 6633, NGC 6572
Virgo
Libra
M62
[ ] Ophiuchus
CORONA AUSTRALIS
Scorpius
LUPUS
SCORPIUS RS Ophiuchi
Sagittarius
This star is a recurrent Shaula nova, which means that it flares brightly every few years. Normally it is too faint to be seen, but occasionally it is easily visible to the naked eye.
Capricornus
Aquarius
Pisces
Globular cluster A globular cluster is a group of many thousands of stars. Through a telescope, a globular cluster appears full and round, like a stellar globe. Globular clusters have very little gas or dust between their stars. Astronomers believe that they are some of the oldest objects in the Milky Way—they could be 10 or 15 billion years old. There are many stars in globular clusters. The brightest are huge red giants. Globular clusters usually contain a few hundred red giant stars. But most of the stars are fainter and lighter than red giants. These are called Population II stars. A specific type of Population II star—called RR Lyrae stars—lives in globular clusters. Astronomers have found that their light pulsates regularly. RR Lyrae stars help astronomers measure the distances from Earth to their clusters. Most globular clusters are similar to one another. One interesting cluster is called Palomar 5, which is about 75,000 light-years from Earth. Astronomers photographed Palomar 5 as it was torn apart by the Milky Way’s gravitational forces. They are now studying the streams of stars left behind. This may help them learn about dark matter in our galaxy.
This image shows a globular cluster in the Milky Way.
More than
the number of globular clusters discovered in the Milky Way
Supernova A type 1 supernova is a star that explodes. When it does so, it suddenly increases in brightness by a factor of many billions; within a few weeks, it slowly fades. As a star nears the end of its life, it keeps shining by burning increasingly heavy elements. Eventually, the star’s core is turned into iron, triggering its final, explosive collapse. The star blasts apart, tossing heavy elements into space. In many cases, a neutron star or a pulsar (a rapidly spinning neutron star) is left behind after the explosion. In our galaxy, the Milky Way, a supernova may be observed by the naked eye only once every few hundred years. In 1054, Chinese astronomers observed the “guest star” that created the Crab Nebula, visible in Taurus. European astronomers Tycho Brahe and Johannes Kepler observed supernovae in, respectively, 1572 and 1604. In 1987, a supernova in the Tarantula Nebula of the Large Magellanic Cloud was easily visible from the Southern Hemisphere.
During a supernova explosion,
elements are blasted into space at speeds of This shows the remains of a supernova called RCW 86, which was witnessed and described by the Chinese in 185 ce.
miles (1,600 km) per second
ecliptic
noun
The path that the Sun appears to trace around the sky, or celestial sphere, each year. Twelve of the constellations around the ecliptic make up the zodiac. The Sun also passes through a thirteenth constellation, Ophiuchus.
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Credits Copyright © 2012 by Scholastic Inc. All rights reserved. Published by Scholastic Inc., Publishers since 1920. scholastic, scholastic discover moretm, and associated logos are trademarks and/or registered trademarks of Scholastic Inc. All rights reserved under International and Pan-American Copyright Conventions. No part of this publication may be reproduced, transmitted, downloaded, decompiled, reverse engineered, or stored in or introduced into any information storage and retrieval system, in any form or by any means, whether electronic or mechanical, now known or hereinafter invented, without the express written permission of the publisher. For information regarding permission, write to Scholastic Inc., Attention: Permissions Department, 557 Broadway, New York, NY 10012. Library of Congress Cataloging-in-Publication Data Available ISBN 978-0-545-38374-5 First edition, May 2012 Scholastic is constantly working to lessen the environmental impact of our manufacturing processes. To view our industry-leading paper procurement policy, visit www.scholastic.com/paperpolicy. Consultant: Dr. Mike Goldsmith Senior Editor: Slaney Begley Senior Art Editor: Alison Gardner Interactive Designer: Tom Forge Visual Content Project Manager: Diane Allford-Trotman Digital Photography Editor: Stephen Chin Image Credits All star maps and artwork by Tim Brown, except as noted below. Title screen: (t) Image Work/amanaimagesRF/Getty Images; (b background) NASA. Contents: (starry background) Vladimir Piskunov/iStockphoto; (water background bl) Arie J. Jager/iStockphoto; (zodiac chart and moon) Neven Bijelic/iStockphoto; (computer icon tr, book icon tr) Vector/Shutterstock. What is the zodiac?: (background) Jerry Schad/Photo Researchers, Inc.; (tr) coolman327/ iStockphoto; (video) Cristian Paunescu/iStockvideo. Horoscopes: (background) Photosani/Shutterstock. The elements: (fire) Sergey Mironov/Shutterstock; (water) nikkytok/Shutterstock; (earth) sandsun/iStockphoto; (air) Elenamiv/ Shutterstock. Seeing the zodiac: (all constellations) Till Credner/Allinthesky.com. Ophiuchus: (br) US Naval Observatory and the Space Telescope Science Institute. Supernova encyclopedia entry: NASA/ESA/JPL-Caltech/UCLA/CXC/ SAO. Globular cluster encyclopedia entry: NASA/JPL-Caltech/Univ. of Wyoming/DSS. Aries: (br) Jay Pasachoff/Science Faction/SuperStock. Supergiant star encyclopedia entry: NASA/JPL-Caltech/Cornell University and University of Leiden. Double star encyclopedia entry: Mark A. Garlick/space-art.
co.uk-http://www.markgarlick.com/pages/contact.htm. Aries horoscope: (cl) Quang Ho/Shutterstock; (cm) Denis Radovanovic/Dreamstime; (cr) Loverpower/ Dreamstime; (bl) Carsten Reisinger/Dreamstime; (bm) Pedro Nogueira/ Dreamstime; (br) George Paul/iStockphoto; (all icons tr) iStockphoto; (all backgrounds) Viktoria/Shutterstock. Aries gallery: (l) Stephen Leshin; (tr) NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University); (cr) John Sanford & David Parker/Photo Researchers, Inc.; (br) Alessandro Falesiedi. Taurus: (br) US Naval Observatory and the Space Telescope Science Institute; (video) ESA/Hubble. Star cluster encyclopedia entry: NASA/JPL-Caltech/UCLA. Supernova encyclopedia entry: NASA/ESA/JPL-Caltech/UCLA/CXC/SAO. Taurus horoscope: (cl) Ilya Gridnev/Dreamstime; (cm) Andres Rodriguez/ Dreamstime; (cr) Photo_Alto/iStockphoto; (bl) Stockbyte/Thinkstock; (bm) Thinkstock; (br) Andres Rodriguez/Dreamstime. Taurus gallery: (l) NASA/JPLCaltech/UCLA; (tr) NASA, ESA, J. Hester and A. Loll (Arizona State University); (cr) Bob Starzynski; (br) NASA/JPL/Space Science Institute. Gemini: (br) US Naval Observatory and the Space Telescope Science Institute. Open cluster encyclopedia entry: NASA/JPL-Caltech/UCLA. Nebula encyclopedia entry: NASA/JPL-Caltech/Univ. of Ariz. Gemini horoscope: (cl) Emirmd/Dreamstime; (cm) Judwick/Dreamstime; (cr) Pedro Nogueira/Dreamstime; (bl) Derek Latta/ iStockphoto; (bm) Andres Rodriguez/Dreamstime; (br) Leremy/Dreamstime. Gemini gallery: (l) NASA, ESA, Andrew Fruchter (STScI), and the ERO team (STScI + ST-ECF); (tr) N. A. Sharp (NOAO), AURA, NSF; (br) Doug Zubenel (TWAN). Cancer: (br) US Naval Observatory and the Space Telescope Science Institute; (video) NASA, Spitzer Space Telescope. Giant star encyclopedia entry: NASA, Spitzer Space Telescope. Cancer horoscope: (cl) Rmarmion/Dreamstime; (cm) Andres Rodriguez/Dreamstime; (cr) Sergiyn/Dreamstime; (bl) Leremy/ Dreamstime; (bm) Sbhoso/Dreamstime; (br) Sherwin McGehee/iStockphoto. Cancer gallery: (l) 2MASS Atlas Image Gallery: The Messier Catalog; (tr) NASA/ ESA/G. Bacon (STScI); (cr) Jason T. Ware/Photo Researchers, Inc.; (br) Jimmy Westlake (Colorado Mountain College). Leo: (br) US Naval Observatory and the Space Telescope Science Institute. Meteor shower encyclopedia entry: Laura Stone/Dreamstime. Red dwarf encyclopedia entry: NASA/Walt Feimer. Leo horoscope: (cl) ssuaphotos/Shutterstock; (cm) Quang Ho/Shutterstock; (cr) ZoneCreative/iStockphoto; (bl) Andres Rodriguez/Dreamstime; (bm) Franck Boston/Shutterstock; (br) George Paul/iStockphoto. Leo gallery: (tl) NASA, ESA, Hubble Heritage, S. Van Dyk (JPL/IPAC), R. Chandar (U. Toledo), D. De Martin & R. Gendler; (tr) ESO, INAF-VST, OmegaCAM; (cr) NASA, ESA, Hubble Heritage (STScI/AURA); (bl) Torsten Boeker, Space Telescope Science Institute, and NASA/ESA; (bc) Volker Wendel; (br) Russell Croman/Photo Researchers, Inc. Virgo: (br) US Naval Observatory and the Space Telescope Science Institute. Virgo cluster encyclopedia entry: Digitized Sky Survey, Palomar Observatory, STScI. Quasar encyclopedia entry: NASA/CXC/SAO/P. Green et al. Optical: Carnegie Obs./Magellan/W. Baade Telescope/J. S. Mulcahey et al. Virgo horoscope: (cl) Andres Rodriguez/Dreamstime; (cm) Olga Bogatyrenko/ Dreamstime; (cr) Nikhil Gangavane/Dreamstime; (bl) Suprijono Suharjoto/ Dreamstime; (bm) Daniel Loiselle/iStockphoto; (br) Sgcallaway1994/Dreamstime. Virgo gallery: (tl) NASA/JPL-Caltech/UCLA; (tc) NASA, STScI, WikiSky; (tr) NASA/JPL-Caltech; (bl) NASA/JPL-Caltech/University of Arizona; (br) NASA
and The Hubble Heritage Team (STScI/AURA). Libra: (br) Jay Pasachoff/Science Faction/SuperStock. Libra horoscope: (cl) Igor Vorobyov/Dreamstime; (cm) kycstudio/iStockphoto; (cr) Leremy/Dreamstime; (bl) Raluca Tudor/Dreamstime; (bm) ZoneCreative/iStockphoto; (br) Andres Rodriguez/Dreamstime. Libra gallery: (l) Lynette R. Cook; (tr) Stephane Udry, Michel Mayor (Geneva Obs.) et. al, Image: DSS, Skyview; (br) Francois du Toit. Scorpio: (br) US Naval Observatory and the Space Telescope Science Institute. Milky Way encyclopedia entry: ESO/Yuri Beletsky. Antares encyclopedia entry: Dick Locke. Supergiant star encyclopedia entry: NASA/JPL-Caltech/Cornell University and University of Leiden. Scorpio horoscope: (cl) Jacek Chabraszewski/Dreamstime; (cm) Pedro Nogueira/Dreamstime; (cr) Isabel Poulin/Dreamstime; (bl) Anatoly Maslennikov/Dreamstime; (bm) Hughstoneian/Dreamstime; (br) Zts/ Dreamstime. Scorpio gallery: (l) NASA/JPL-Caltech/UCLA; (tr) T2KA, KPNO 0.9m Telescope, NOAO, AURA, NSF; (cr) F. R. Ferraro (ESO/Bologna Obs.), M. Shara (STSci/AMNH) et al., & the Hubble Heritage Team (AURA/STScI/NASA); (br) Allan Cook & Adam Block, NOAO, AURA, NSF. Sagittarius: (br) US Naval Observatory and the Space Telescope Science Institute; (video) NASA/CXC/A. Hobart. Black hole encyclopedia entry: Ute Kraus, Institute of Physics, Universität Hildesheim/Wikipedia. Cosmic dust encyclopedia entry: JeanCharles Cuillandre (CFHT) & Giovanni Anselmi (Coelum Astronomia), Hawaiian Starlight. Sagittarius horoscope: (cl) ranplett/iStockphoto; (cm) Emirmd/ Dreamstime; (cr) PondPond/Shutterstock; (bl) Christophe.rolland1/Dreamstime; (bm) Wavebreakmedia Ltd/Dreamstime; (br) Andres Rodriguez/Dreamstime. Sagittarius gallery: (l) NASA/JPL-Caltech/Penn State; (tr) Hunter Wilson; (cr) Jean-Charles Cuillandre (CFHT) & Giovanni Anselmi (Coelum Astronomia), Hawaiian Starlight; (br) Steven Mazlin, Jim Misti. Capricorn: (br) Jay Pasachoff/ Science Faction/SuperStock. Capricorn horoscope: (cl) zorani/iStockphoto; (cm) Thinkstock; (cr) Elena Elisseeva/Shutterstock; (bl) Dny3dcom/Dreamstime; (bm) Annworthy/Dreamstime; (br) Leremy/Dreamstime. Capricorn gallery: (l) Friendlystar at en.wikipedia; (tr) NASA, STScI, WikiSky; (br) John Chumack/ Photo Researchers, Inc. Aquarius: (br) US Naval Observatory and the Space Telescope Science Institute. Extrasolar planet encyclopedia entry: NASA/JPLCaltech/Palomar Observatory. Globular cluster encyclopedia entry: NASA/JPLCaltech/Univ. of Wyoming/DSS. Aquarius horoscope: (cl) Manuela Thurnher/ Dreamstime; (cm) Jirˇí Kábele/Dreamstime; (cr) Minnie Menon/iStockphoto; (bl) Jonathan Ross/Dreamstime; (bm) Michael Smith/Dreamstime; (br) Eduard Stelmakh/Dreamstime. Aquarius gallery: (tl, bl) NASA/STScI/WikiSky; (bc) Digitized Sky Survey; (r) NASA/JPL-Caltech/ESA. Pisces: (br) Jay Pasachoff/ Science Faction/SuperStock; (video) NASA Goddard Space Flight Center/NCSA. Spiral galaxy encyclopedia entry: NASA/JPL-Caltech; X-ray: CXC/Univ. of Maryland/A. S. Wilson et al.; Optical: Pal.Obs. DSS; IR: VLA: NRAO/AUI/NSF. Asterism encyclopedia entry: Till Credner/Allinthesky.com. Pisces horoscope: (cl) Cornelia Pithart/Dreamstime; (cm) Ayzek09/Dreamstime; (cr) Rebecca Abell/ Dreamstime; (bl) Raluca Teodorescu/Dreamstime; (bm) Leremy/Dreamstime; (br) Arvind Balaraman/Dreamstime. Pisces gallery: (l) NASA, ESA, and The Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; (tr) Stephen Leshin; (cr) Gerald Rhemann; (br) Sephirohq/Wikipedia. Many thanks to Grolier OnlineTM for articles and assistance.
