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Star : Luminosity
1. Which statement best describes stars?
A.
B.
C.
D.
large planets that are composed mostly of gases
celestial bodies made up of gas that give off light
faint dots of light that can be seen from Earth’s surface
objects that form in the outer parts of the solar system
2. What characteristic of stars is measured by luminosity?
A.
B.
C.
D.
brightness
size
temperature
distance from Earth
3. Which of the following units is used to express the size of stars?
A.
B.
C.
D.
kilometer
light-year
solar radius
astronomical unit
4. Which of the following pairs of terms directly relates to the actual brightness of a star?
A.
B.
C.
D.
absolute magnitude and luminosity
apparent magnitude and luminosity
size and luminosity
absolute magnitude and apparent magnitude
Questions 5 -7
Anthony’s teacher posted the following chart on the wall of his classroom.
5. The teacher asked the class to list various items from the chart in order from
brightest to dimmest apparent magnitude. Which object should Anthony list first?
A.
B.
C.
D.
Venus
full moon
Barnard’s Star
Alpha Centauri
6. Based on the chart, which tool could be used to observe an object with an apparent
magnitude of 25?
A.
B.
C.
D.
naked eye
binoculars
Hale telescope
1-m telescope
7. Which of the following can be concluded from the information in the chart?
A. The sun has the greatest absolute magnitude of the objects listed.
B. Sirius’ apparent magnitude is greater than Betelgeuse’s but dimmer than
Alpha Centauri’s.
C. No tool that is listed can be used to view objects with an apparent
magnitude greater than 30.
D. People can see all of the celestial bodies listed in the chart without using
any special tools.
8. The table below lists the characteristics of various stars.
Star
Temperature (K)
A
B
C
D
10,000
7,000
31,000
15,000
Distance from
Earth (ly)
23
132
58
989
Apparent
Magnitude
– 1.44
1.23
– 0.31
9.54
Based on the information in the table, list the stars from dimmest to brightest when
viewed from Earth’s surface.
A.
B.
C.
D.
D, B, C, A
A, B, C, D
D, A, B, C
A, C, B, D
.
9. Natasia examined a table that lists the characteristics of four stars.
Star
Temperature (K)
A
B
C
D
10,000
7,000
31,000
15,000
Distance from
Earth (ly)
23
132
58
989
Apparent
Magnitude
– 1.44
1.23
– 0.31
9.54
Which star would appear the dimmest from Earth’s surface?
A.
B.
C.
D.
star A
star B
star C
star D
Answers
1.
B
• A is incorrect because planets are celestial bodies that typically orbit stars.
• B is correct because stars are large bodies of gas that give off light.
• C is incorrect because some of the faint dots that can be seen from Earth’s surface
are planets and comets.
• D is incorrect because comets, not stars, form in the outer parts of the solar system.
2.
A
• A is correct because luminosity expresses how bright a star actually is, not how bright
it appears from Earth’s surface.
• B is incorrect because the size of a star, not luminosity, is derived from a star’s solar
radius.
• C is incorrect because surface temperature, not luminosity, is derived from the color
of a star.
• D is incorrect because distance from Earth and apparent magnitude are used to
calculate absolute magnitude, which is the measure of luminosity.
3.
C
• A is incorrect because kilometers are too small to use to measure the size of many
stars and would result in numbers that are cumbersome to use.
• B is incorrect because light-years are used to measure distances in the universe and
would be too large to use as a measure of the size of stars.
• C is correct because the radius of the sun, one solar radius, is used to measure the
size of other stars.
• D is incorrect because astronomical units are equal to the mean distance between
Earth and the Sun, which makes them too large to be used to measure the size of
stars.
4.
A
• A is correct because absolute magnitude is a measure of a star’s luminosity, which is
how bright a star actually is.
• B is incorrect because apparent magnitude can be used to calculate absolute
magnitude, but the term does not relate directly to the actual brightness of a star.
• C is incorrect because the size of a star does not necessarily correlate to the
brightness of a star.
• D is incorrect because apparent magnitude can be used to calculate absolute
magnitude, but the term does not relate directly to the actual brightness of a star.
5.
B
• A is incorrect because the apparent magnitude of Venus is bigger than the apparent
magnitude of the full moon, so it is dimmer.
• B is correct because of the objects listed, the full moon has the smallest apparent
magnitude, making it the brightest object observed from Earth.
• C is incorrect because Barnard’s Star has the biggest apparent magnitude in the
chart, so it is the dimmest object listed.
• D is incorrect because Alpha Centauri has a bigger apparent magnitude than the full
moon and Venus, so it is dimmer.
6.
C
• A is incorrect because any objects with an apparent magnitude bigger than 6 cannot
be seen with the naked eye.
• B is incorrect because any objects with an apparent magnitude bigger than 10 cannot
be seen with binoculars.
• C is correct because the Hale telescope can be used to observe an object of
apparent magnitude 27.
• D is incorrect because a 1-m telescope can be used to observe objects having an
apparent magnitude of 19 or brighter.
7.
C
• A is incorrect because based on the information in the chart, it is not possible to tell
which body has the greatest absolute magnitude.
• B is incorrect because Sirius has a smaller apparent magnitude than Alpha Centauri,
which has a smaller apparent magnitude than Betelgeuse.
• C is correct because the most powerful tool listed is the Hubble telescope, which can
be used to view objects of apparent magnitude 30 or brighter.
• D is incorrect because Barnard’s Star cannot be observed with the naked eye.
8.
A
• A is correct because the star with the biggest apparent magnitude should be listed
first and the remaining stars should be listed in order of smaller apparent magnitude.
• B is incorrect because it simply lists the stars in the order they appear in the table,
which does not coincide with apparent magnitude.
• C is incorrect because it disregards the negative signs in the apparent magnitude
values.
• D is incorrect because it lists the brighter stars first
9.
D
• A is incorrect because star A has a negative apparent magnitude, which means it is a
brighter star.
• B is incorrect because even though star B has a big apparent magnitude, it does not
have the biggest apparent magnitude of the stars listed.
• C is incorrect because stars that have smaller apparent magnitudes appear brighter.
• D is correct because star D has the biggest apparent magnitude, which means it is
the dimmest star