Observing Objects in Space

T

IN

IO

N

86

V EST IGA

S

pace exploration has always been aided by the work of astronomers. An astronomer is a scientist who studies objects and events beyond the Earth’s atmosphere, such as the composition or movement of stars and planets. A star is a huge ball of gas that gives off heat and light. A planet, which is smaller than a star, revolves around a star and reflects that star’s light. Although many objects in the night sky can be seen with the “naked eye,” that is, without telescopes or binoculars, telescopes help astronomers make more detailed observations of space objects. For example, for a long time people thought they saw oceans and lakes on the Moon. Using telescopes, astronomers realized that these were fields of hardened volcanic lava.

CHALLENGE What can you observe about objects in space?

G-7

Activity 86 • Observing Objects in Space

PROCEDURE 1. Each photograph on the next page shows a space object as seen through a powerful telescope. In your science notebook, make a table like the one below.

Observing Space Objects Space Object Number

Observations

Category

1 2 3 4 5 6

2. Carefully examine the six space objects shown. Look for ways to tell the objects apart. 3. Discuss your observations with your partner, and then record them in the “Observations” column of your table. Leave the “Category” column blank for now. 4. Discuss your observations with the other pair in your group. Review the tables together, and add any new observations about the space objects. 5. In your group of four, decide whether you think the space objects are planets, stars, or “other.” Record your ideas in the “Category” column of the table. 6. Describe in your science notebook how you selected the category for each object in the photographs.

G-8

Observing Objects in Space • Activity 86

Space Objects

1

2

3

4

5

6

G-9

Activity 86 • Observing Objects in Space

ANALYSIS 1. Which objects were most difficult to categorize? Explain what made it difficult. 2. What other observations or information about the objects would help you identify them more easily? 3. What technological inventions have helped us describe and identify space objects?

EXTENSION On a clear night take Student Sheet 86.1, “Night Sky Observations,” a pencil, and a flashlight, and go outside. Find a place where you have a good view of the sky and you are as far away as possible from any lights. Look carefully at the sky, and find five bright, but different, objects. Use the information on the next page to guide your observations. Record your observations on your Student Sheet. Look at those same objects on five different nights and identify how they have changed.

G-10

Observing Objects in Space • Activity 86

Field Study of the Night Sky The objects described below are visible with the “naked eye,” and can usually be seen on a dark clear night. Stars are the most common object we see in the night sky. The light from a star comes from so far away that it acts as a single ray of light. Stars seem to “twinkle” because the Earth’s atmosphere refracts, or redirects, the ray of light. Stars appear to move together across the sky during the night. Planets may be difficult to distinguish from stars. If an object in the sky looks similar to a star but doesn’t twinkle as much or looks fuzzier, it is likely to be a planet. Planets appear as disks when magnified with binoculars or a telescope. Although much smaller than stars, they can appear larger because they are much closer to Earth. Earth’s Moon looks like the largest object in the night sky because it is the closest object to Earth. The phase of the Moon changes during the lunar cycle. Other planets have moons but they are too small or too distant to be seen without a telescope. Satellites and jets move quickly across the night sky and often appear to blink regularly. Sometimes they can look very similar to each other. Most satellites take about 90 minutes to orbit the Earth, so if the object you are observing comes back along the same path in that time, it is probably a satellite. Meteors are small, bright objects that speed across the sky for a few seconds and appear to leave a trail. Meteors are often mistakenly called “shooting stars” or “falling stars” but they are not stars at all. Meteors are pieces of rock that are falling through the atmosphere and usually burn up before they hit the ground. Meteors that reach Earth’s surface are called meteorites. Galaxies are collections of billions of stars. When conditions make one or more of them visible, each galaxy appears as a fuzzy patch of sky. Only a few galaxies can be seen with the naked eye because most are too distant. Our galaxy, sometimes called the Milky Way, is shaped like a disc. When we look out along the plane of the disk, we are looking toward billions of distant stars that appear as a hazy band of light.

G-11