Astronomy final
The surface temperature of a white dwarf star
decreases from millions of degrees K to zero
The core of a red supergiant star stops shrinking because its
electrons touch each other
Stars that are much less massive than our Sun
form more slowly and burn slower
In an evolved high-mass star, when the electrons combine with protons to form a pure neutron core, the reaction
generates a neutrino burst.
When a star first moves o§ the main sequence
its surface temperature drops and its brightness Örst stays about the same and then increases
Stars appear to twinkle because
of turbulent air in our atmosphere that bends the starlight
Neutron stars are often observed as
pulsars
To see small but bright objects such as the ice caps on Mars, you would need a telescope with large
resolving power
A black hole that has formed from the collapse of a star is expected to be
similar in size to a neutron star
The lower left of a Hertzsprung-Russell diagram is where one finds
white dwarf stars
Nuclear fusion requires high temperatures because nuclei
(repel each other.)
When the hydrogen fuel runs out at the center of a main sequence star, the star
(swells up and its surface temperature decreases
Which of the following spectral types corresponds to a star on the main sequence?
(G2V
The mass of a carbon atom is 12.00amu while the mass of a helium-4 atom is 4.003amu. If a gamma ray photon splits a carbon atom into three Helium atoms, how much energy is converted into mass?
(0.009amu)
The apparent brightness of our Sun is roughly 1000 watts per square meter. At a distance of 30 times the Earth-Sun distance, the apparent brightness of our Sun would be
(1.1 watts per square meter.)
Suppose that the color and behavior of a star identify it as a type that we know has absolute magnitude ñ3. If the starís apparent magnitude is found to be 2, how far away is it?
(100 parsecs.)
The star epsilon-Eridani shows a heliocentric stellar parallax near 1/3 seconds of arc. The distance from our Sun to epsilon-Eridani is nea
(3 parsecs
We see what appears to be a single star. However, when the light from the star is put through a spectrometer, we see that its spectrum is shifting back and forth. The star is most likely
(a single-line spectroscopic binary system.)
A star that evolves o§ the main sequence in about 10 million years probably has
(about 20 times the mass of our Sun.
When we use a Hertzsprung-Russelll plot to describe the evolution of a collapsing gas cloud to a protostar and then to a regular star, we find that the objects position on the plot
(begins far from the main sequence and moves onto it, where it stops.)
When the temperature of a gas decreases, its molecules
(move slower.)
A star with an absolute magnitude of 8:4 and an apparent magnitude of 1:0 would appear in our sky as a sta
(of dazzling brightness.
Black holes are often discovered by observing the shifting of spectral lines in an ordinary star that they are orbiting. Careful measurements of the shifting spectral lines can provide
(only a minimum mass for the black hole
A mirror that is shaped like a shallow bowl sitting on the table with its open end facing up will focus light that comes
(vertically down from above.
Which of the following magnitudes corresponds to the dimmest star?
+4
A star is seen to move by 0:4 seconds of arc between March 1, 1999 and September 1, 1999 and then back to its starting point on March 1, 2000. What is the parallax angle for this star?
0:2 seconds of arc.
The velocity of sound waves is roughly the same for all wavelengths. Suppose that a sound wave has a wavelength of one meter and a frequency of 500Hz. The wavelength of a 1000Hz sound wave would then be
1/2 m.
A star with a distance modulus of zero is at a distance of
10 parsecs.)
A star is observed to have an apparent brightness which is 106 times its absolute brightness. How far away is it?
10,000 parsecs
Our Sun is a G2V star with absolute magnitude 4:8. Suppose that a star of spectral type G2V is observed to have apparent magnitude 9:8. How far away is it?
100 parsecs.
Compared to a magnitude 11 star, a magnitude 1 star would be
10; 000 times as bright
You hear a 1000Hz tone from a radio that is 10 feet away from you and listen for 4 seconds. How many pressure maxima pass by your ear?
4000
The violet lines in the Hydrogen spectrum are normally seen with wavelengths 410 nm and 434 nm. In the light of a star that is moving away from us, we might expect to see those lines at wavelengths of
415 nm and 439 nm
In the Hertzsprung-Russelll Diagram shown, which point represents a star of type B with absolute magnitude
A
You see a reáecting telescope with a short, stubby tube and the eyepiece at the back. This telescope uses the
Cassegrain Focus
Which of the following pictures is the most like the main sequence on a Hertzsprung-Russelll Diagram?
D
Of all the things that might go wrong with distances found by using the method that astronmers refer to as the "distance ladder," which of these is the one that an astronomer would say is most likely?
Distant objects are not behaving the same as nearby objects
Which of the following spectral classes corresponds to the lowest surface temperature (on this list)?
K
The star Wemadeit shows a stellar parallax angle of 0.2 seconds of arc while the star Waytoofar shows a stellar parallax angle of 0.3 seconds of arc. From this, you can conclude that
Waytoofar is closer to our Sun than Wemadeit
The object Gliese 229B glows in the infrared but is much cooler and dimmer than a class M star and shows traces of lithium that a normal star would quickly burn up in the nuclear reaction that occurs in its core. This
a brown dwarf.
A nova occurs when
a white dwarf steals fuel from a neighbor.
High protostellar winds of ejected gas occur
between the initial contraction and the ignition of nuclear burning.
For stars on the main-sequence, stars with increasing mass have
increasing surface temperature and absolute brightness
Heliocentric Stellar Parallax causes
nearby stars to shift back and forth once a year
Which of the following particles has almost the same mass as a proton?
neutron
The velocity of a wave is defined to be
the distance traveled by a crest divided by the time taken
The helium flash refers to
the explosive ignition of a starís helium core
In order to use spectroscopic parallax to find the distance to a star, you need to know
the spectral type and luminosity class (B2V for example) and the apparent magnitude
Because mirrors only use one surface, they have a big advantage over lenses: They can be
thinner and larger in diameter.)
When the core of a star collapses while inside the star, the result is a
type II supernova