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WorksheetsAstronomy Part 5
Total questions: 20
Worksheet time: 40mins
Name
Class
Date
1.
How do astronomers measure the distance to a nearby star?
a)
They measure the change in its apparent brightness over a period of six months because of the Earth's orbital motion.
b)
They observe the apparent change in its position over one night because of the motion of the observer on a rotating Earth.
c)
They observe the apparent change in its position with respect to other, more distant stars over a period of six months.
d)
They measure the change in position of absorption lines in the star's spectrum over a period of six months.
2.
A star of magnitude +8 is
a)
brighter than a star of magnitude +5.
b)
fainter than a star of magnitude +5.
c)
impossible: the magnitude scale runs only from +1 to +6.
d)
the same brightness as a star of magnitude +5, but hotter.
3.
A star of magnitude -1 is
a)
impossible.
b)
fainter than a star of magnitude +1.
c)
the same brightness as a star of magnitude +1.
d)
brighter than a star of magnitude +1.
4.
According to the inverse-square law, if two stars have the same luminosity and if one star is nine times farther away than the other, then
a)
the more distant star would be 81 times fainter.
b)
the more distant star would be 3 times fainter.
c)
the more distant star would be 81 magnitudes fainter.
d)
the more distant star would be 3 magnitudes fainter.
5.
In the visible spectra of stars, absorption lines of hydrogen are produced when electrons are excited to higher levels (the Balmer series). If hydrogen absorption lines are very strong in the visible spectrum of a particular star, what is this star's surface temperature?
a)
very high temperature, about 40,000 K, because at lower temperatures too many hydrogen atoms have their electrons in the ground state (n = 1) and cannot absorb in the Balmer series
b)
relatively low temperature, about 6000 K (similar to the Sun), because at lower temperatures too many hydrogen atoms are in the ground (n = 1) state, and at higher temperatures too many have had their electrons completely ejected
c)
relatively high temperature, about 10,000 K, so that significant numbers of electrons are excited from the ground state, n = 1, to the first excited state, n = 2, but not too many of them have been ejected completely from the atoms
d)
very low temperature, 3000 K, because at higher temperatures so many hydrogen atoms have had their electrons completely ejected and cannot absorb in the Balmer series
6.
Hydrogen is the most abundant atomic species in the Sun. Why are the absorption lines from hydrogen very weak in the solar spectrum?
a)
The Sun's temperature is so high that most hydrogen atoms are completely ionized and therefore have no electrons that can absorb light.
b)
The Sun's temperature is so high that most electrons in hydrogen atoms are at levels above the second level and therefore cannot absorb at visible wavelengths.
c)
The Sun's temperature is so low that the hydrogen is mostly in molecular form, and Balmer absorption does not occur in molecular hydrogen.
d)
The Sun's temperature is so low that very few electrons in hydrogen atoms are excited to the second energy level, from which absorption of visible light can occur.
7.
Which of the following sequences of stellar classification types shows stars in order of increasing surface temperature?
a)
B2, G6, G9, K0
b)
K0, G9, G6, B2
c)
K0, G6, G9, B2
d)
B2, G9, G6, K0
8.
A certain star is seen to have a relatively low surface temperature but a very high luminosity. What can we conclude from these observations?
a)
The star must be very large.
b)
The star is a red dwarf.
c)
The star is a main-sequence star, about the size of the Sun.
d)
The star must be blue in color because of the very high luminosity.
9.
A distant star of spectral type M is found to be very bright and easily visible from Earth. How would you describe it, and what would be its place in the Hertzsprung-Russell diagram?
a)
red dwarf on the main sequence; lower-right-hand corner of the H-R diagram
b)
blue dwarf on the main sequence; upper-left-hand corner of the H-R diagram
c)
yellow supergiant, in the upper middle of the H-R diagram
d)
red supergiant; upper-right-hand corner of the H-R diagram
10.
If a star is found to evolve so that it moves from the main sequence to the red-giant area of the Hertzsprung-Russell diagram (remember, red stars are cool), which of the following changes will have occurred? (Think about H-R diagram activity to help you)
a)
The star's mass will have become greater.
b)
The star's surface temperature will have increased.
c)
The star will have expanded.
d)
The star's luminosity will have decreased.
11.
Two stars, one classified F7 and the other K3, have the same apparent magnitude. From this information, we know that the K3 star is
a)
closer to the Sun than the F7 star is.
b)
farther from the Sun than the F7 star is.
c)
larger than the F7 star is.
d)
hotter than the F7 star is.
12.
Aldebaran, a star in the constellation Taurus, has a spectral-luminosity class of K5 . This tells us that Aldebaran is a
a)
hot supergiant.
b)
cool giant.
c)
cool supergiant.
d)
hot giant.
13.
Among the stars in the vicinity of the Sun,
a)
almost all are single stars, like our Sun.
b)
almost all are members of a system of many stars, such as a cluster.
c)
about a third to a half are members of a binary system.
d)
almost all are members of a binary system
14.
In a binary-star system with stars of unequal mass, the center of mass, about which both stars orbit in ellipses, is always on the line joining both stars and
a)
closer to the less massive star.
b)
exactly centered between the two stars, as required by Newton's laws.
c)
closer to the more massive star.
d)
closer to the more massive or the less massive star, depending on the orbital speeds of the two stars.
15.
Parallax measurements are taken of stars to determine:
a)
stellar masses.
b)
stellar surface temperatures.
c)
stellar diameters.
d)
stellar distances from Earth.
16.
Mira and Barnard’s star have different luminosities, as can be seen from the Hertzsprung-Russell diagram. This difference comes about because Mira has a
a)
larger diameter than Barnard’s star.
b)
smaller diameter than Barnard’s star.
c)
higher surface temperature than Barnard’s star
d)
lower surface temperature than Barnard’s star.
17.
A star has a high luminosity (102 solar luminosities) and a surface temperature of 3500 K. What type of star is it?
a)
A high mass–main sequence star
b)
A low mass–main sequence star
c)
A red giant
d)
A theoretically predicted object that has not yet been observed
18.
Betelgeuse has a very high luminosity (40,000 times brighter than our Sun), but its surface is cool (less than 4000 K). Which of the following explains this?
a)
Betelgeuse must have a much smaller surface area than the Sun.
b)
Betelgeuse is at the lower end of the main sequence.
c)
Betelgeuse is at the upper end of the main sequence.
d)
Betelgeuse must have a much larger surface area than the Sun.
19.
The masses of stars are most accurately measured by observing:
a)
their colors
b)
their rotation rates
c)
their orbits in binary systems
d)
their temperatures
20.
The spectral type of the Sun is G and the spectral type of the star Antares is K. These facts imply that Antares
a)
has a lower luminosity than the Sun.
b)
is hotter than the Sun.
c)
has a higher luminosity than the Sun.
d)
is cooler than the Sun.
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