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Chapter 4.2 Astronomy Review
The Scale of the Universe
Understanding Main Ideas
If the statement is true, write true. If the statement is false, change the underlined word
or words to make the statement true.
1.
The spacecraft Voyager is 16,000,000,000 km away from Earth.
That is the same as 1.6 × 1010 km.
An astronomer says that his house cost $2.9 × 105. That is
2.
$2,900,000.
3.
A light-year is a measure of time on an astronomical scale.
4.
Astronomers often use parallax to measure distances to stars.
5.
Refraction makes nearby stars look like they shift position
against the background of stars between winter and summer viewings from Earth.
6.
The solar system is all of space and everything in it.
Building Vocabulary
Write a definition for each of these terms on the lines below.
7. light-year
8. parallax
9. universe
10. scientific notation
135D
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The Scale of the Universe
Read the passage and study the table below. Then use a separate sheet of paper to
answer the questions that follow.
The Apparent Magnitude Scale
The apparent magnitude of stars was first recorded by the Greek astronomer Hipparchus about 160 B.C.
Hipparchus grouped stars according to their brightness or magnitude. He called the twenty brightest
stars first magnitude stars. Stars half that bright were second magnitude. Third magnitude stars were
half as bright as second magnitude stars, and so on. Modern astronomers have changed Hipparchus’s
system a little. In the modern system, an object of magnitude 1 appears 100 times as bright as one of
magnitude of 6. This means that if two objects are separated by one unit of magnitude, the brighter
object appears about 2.5 times as bright as the dimmer one. A star of magnitude 1 is about 2.5 times
as bright as a star of magnitude 2. Using this scale, the dimmer the object, the larger the magnitude
number.
What about very bright objects? Remember, the brighter an object appears, the lower the magnitude
number. Very bright objects have negative magnitudes. Sirius, the brightest star in the sky (except for the
sun), has a magnitude of −1.5. Venus is the brightest planet. Its brightness varies, but at its brightest, its
magnitude is −4. The suns magnitude is −26.5.
Object
Apparent Magnitude
−26.50
Sun
Venus (maximum brightness)
−4.00
Mars (maximum brightness)
−2.00
Procyon
0.36
Regulus
1.36
Dimmest visible to the naked eye
6.00
Dimmest visible with binoculars
10.00
1. What is the difference between the magnitudes of the bright stars
Regulus and Procyon? Which is brighter? How much brighter is it
than the dimmer one?
2. How much brighter is Venus than Mars?
3. What is the difference between the magnitude of the dimmest star
that is visible with the naked eye and the magnitude of the dimmest
star that can be seen with binoculars? How much brighter is the
former than the latter?
Name
Date
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The Scale of the Universe
Write the letter of the correct answer on the line at the left.
1.
In space, light travels at a speed of
about 300,000,000 m/s. Which expresses
that speed correctly in scientific notation?
A 300,000 km/s
B 3 × 109 m/s
C 3 × 108 m/s
D 3 × 107 m/s
2.
A star is 9 × 1012 meters from Earth.
What is that number in expanded form?
A 900,000,000,000 meters
B 9,000,000,000,000 meters
C 90,000,000,000,000 meters
D 9.0 × 1012 meters
3.
After six months, an astronomer
notices that star A moves a greater
distance than star B. Which conclusion is
correct?
A Star A is closer than star B.
B Star A and star B are equally far away.
C Star A is farther away than star B.
D More observations are necessary to
determine which star is farther away.
4.
A star looks like it’s located one place
in the sky in January and a different place
in June. What is this phenomenon called?
A a light-year
B parallax
C refraction
D scientific notation
Fill in the blank to complete each statement.
5.
uses powers of ten to write very large or
very small numbers in shorter form.
6. The
is made up of all of space and everything in it.
7. A light-year is a measure of
.
8. Astronomers use
to measure the distance to stars that are
within several hundred light-years of Earth.
9. The distance light travels through space in a year is one
10. Parallax is the apparent change of
at it from different places.
.
of an object when you look
135F