Astronomy Final Part 2
Order the following stages in a star's evolution:
1. Main-Sequence Star, 2. First red giant stage, 3. Fusion of helium to carbon in the core, 4. Ejection of a planetary nebula
Match the types of galaxies to facts about them
1. They contain little gas and dust and few new stars (elliptical galaxies), 2. The reddest of the three types of galaxies (elliptical galaxies), 3. They contain new stars, but no disk (irregular galaxies), 4. Young stars are found in the disk (spiral galaxies)
Two main-sequence stars have the same spectral type, but one is 10 light years from the Earth and the other is 1000 light years from the Earth. The farther star appears to be
10,000 times fainter
Which of the following is the most likely mass of the star shown in the diagram above?
12 solar masses
A star has a radius 4 times larger than the Sun, but the same temperature. How bright is it compared to the Sun?
16 times brighter
The heavy black line on the graph above shows the temperature in Kelvin at different distances from the Sun (expressed in astronomical units, or AU) at the time when the planets were originally forming. Beyond approximately what distance from the Sun would you expect Jovian planets to form? (Rock melts at temperatures above about 1200 K; the boiling temperature of water is 373 K; the freezing temperature of water is 273 K; and methane and ammonia can exist as ice at temperatures below about 100 K.)
2 AU
In what century were galaxies first shown to lie outside the Milky Way?
20th Century
If the stars Ain and Suhail have the same apparent brightness, but Ain is 5 times farther away from us than Suhail, then Ain's luminosity is ___________ times the luminosity of Suhail
25
When we observe stars near the center of the Milky Way galaxy, we detect light that was emitted from those stars about
25,000 years ago
How many times more massive is the Sun than the Earth?
300,000
The spectra of two stars are shown above, with the wavelength of light on the x axis and the amount of light received at that wavelength on the y axis. Which star is hotter?
A
Two stars are shown above, with sizes and colors as indicated by the circles. Which star is more luminous? (A=Large blue) (B= orange suns)
A
Two stars are shown above, with sizes and colors as indicated by the circles. Which star is more luminous? (A=large blue) (B=small blue)
A
What kind of star is at the center of a planetary nebula?
A White Dwarf
The event that marks the end of a star's evolutionary life before becoming a white dwarf is
A planetary nebula
The Milky Way is
A spiral galaxy
Which of these stars will end its main sequence lifetime most rapidly?
A very massive star, since more massive stars consume their hydrogen more rapidly.
Compared to the evolutionary track of a star like the Sun, the track of a high mass star
All of the above
Consider two stars in the constellation Pasta. Alpha Tortellini is bright at ultraviolet (UV) wavelengths and dim in at infrared (IR) wavelengths, while Beta Ziti is dim in the UV and bright in the IR. Which star is hotter?
Alpha Tortellini
A binary star that varies in apparent brightness as one member of the binary passes in front of the other is
An eclipsing binary
The radial velocity curve for a star with an extrasolar planet is shown above. Positive velocities show when the light from the star is redshifted, and negative velocities show when the light from the star is blueshifted. At time A, in what direction is the star moving?
Away from you
The mass of a star may be determined
By studying its orbit around a binary companion
planet and its parent star orbit their common______, though it is far closer to the star than to the planet.
Center of mass
Compared to the surrounding photosphere, sunspots are
Cooler
Compared to a main-sequence star of type O, a main-sequence start of type K is:
Cooler and less massive
An astronomer observes a set of sunspots forming a vertical line, as shown by the top picture in the image above. Which of the four images in the bottom row shows how the Sun would mostly likely appear several days later?
D
Suppose that the surface temperature of the Sun were to double. It would have the same luminosity if, at the same time, its radius
Decreases to one-quarter its former size
In main sequence stars, the pressure to counteract gravity comes primarily from
Energy released through the fusion of hydrogen into helium, since hydrogen is readily available and fuses at the central temperatures of stars.
T/F In its lifetime a star changes all of the hydrogen in its core to energy.
False
T/F It is possible to have a 1-billion-year-old, O-type main-sequence star.
False
T/F The density and temperature in the solar corona are much higher than in the photosphere.
False
The Sun will leave the main sequence after it has
Fused nearly all the hydrogen in its inner core to helium.
Stars are
Gaseous
If a pair of stars seen as a spectroscopic binary is also eclipsing, the maximum Doppler shift in the spectral lines occurs
Halfway between eclipses
After a star has evolved into a red giant, hydrogen burning
Happens only in shells outside the core of the star
After the hydrogen in the Sun's core is depleted by nuclear fusion the core will consist primarily of
Helium
Pulsars usually show all of the following except
High temperature fusion reactions
Compared to a star with mass equal to the mass of the Sun, a main sequence star of 10 solar masses is:
Hotter and more luminous
White dwarf stars
In some cases consist largely of carbon and oxygen
Since 1995, nearly a thousand exoplanets around normal stars have been detected with ground-based optical telescopes. Which of the following statements about these planets is true?
In some cases, they are so close to their parent stars that they complete a full orbit in only a few days.
When a star becomes a red giant, it becomes much brighter because it is
Increasing in size
Most of the mass of the Milky Way galaxy is
Invisible and in the halo
The ____________ satellite has found a huge number of transiting exoplanet candidates.
Kepler
The diagram above shows the radial velocity curve of a star with an extrasolar planet at left, and the orbits of the star and extrasolar planet at right. On the radial velocity curve, positive velocities show when the light from the star is redshifted, and negative velocities show when the light from the star is blueshifted. Given the location marked with the dot on the star's radial velocity curve, at which location (I-L) would you expect the planet to be located at this time?
L
Stars with cool surfaces can be very luminous if they are
Large
The most effective technique to find distances to other galaxies is to look at objects in the galaxies for which we know the
Luminosity
As a one solar mass star evolves into a red giant, its
Luminosity increases while surface temperature decreases
What is plotted on an H-R diagram?
Luminosity versus surface temperature
One billion years from now the Sun will be a
Main sequence star
The amount of energy released in a nuclear fusion reaction is directly proportional to the
Mass difference between the initial components and the final products
The most important feature of binary stars is that they allow us to determine stellar
Masses
The Sun spins on its axis roughly once each
Month
The chemical composition of the Sun 3 billion years ago was different from what it is now in that it had
More hydrogen
Which one of the following statements concerning the Milky Way galaxy is false?
Most of it can be see from Earth at optical wavelengths with a small telescope.
Compare the central temperature of a red giant to the central temperature of the main-sequence star from which it evolved. The red giant's center is
Much hotter
Theorists predicted that the Sun should be producing a large number of______, but for a long time their measured rate on Earth was substantially less than expected.
NO DUCKING IDEA
What can escape from within a black hole?
Neither light nor matter
The sun's luminosity comes primarily from
Nuclear fusion
A black hole is likely to be the end of stellar evolution for what type of main-sequence star?
O
The strongest evidence for a black hole in the center of the Milky Way is
Observed orbits of stars show nearly 4 million times the mass of the Sun is in a region less than 6 light-hours across
The visible light we see from the Sun comes from what part of the Sun?
Photosphere
Which of the following statements about pulsars is true?
Pulsars cannot be rotating white dwarfs because their rotation rate is so high that a white dwarf would be ripped apart.
Which one of these methods is not a way to find planets around other stars?
Radar
What kind of radiation is used to find the location and shape of the Milky Way's spiral arms?
Radio Waves
The speeds of receding galaxies are found by measuring their
Redshifts
In what part of the galaxy are O and B stars most often found?
Spiral arms
Spiral arms are usually the most prominent features in the disk of a spiral galaxy. Which one of these statements about spiral arms is false?
Spiral arms consist mostly of dark matter
Consider the following statements about the three main sequence stars A, B and C. Star A will be a main sequence star for a total of 4.5 billion years. Star B has the same luminosity as the Sun. Star C has a spectral type M. What is true about these stars?
Star A has the greatest mass
A typical white dwarf is closest in size to:
The Earth
Suppose that the Sun were suddenly replaced by a black hole of exactly the same mass. What would happen?
The Earth and the rest of the planets would continue to orbit as usual.
Why do we see no evidence of O and B main sequence stars in elliptical galaxies?
The O and B main-sequence stars once in these galaxies have evolved off the main sequence, and no new stars are forming
The 21-cm line observed by radio astronomers comes from
The atomic hydrogen spin-flip transition
Fusion in the core of a main sequence star changes the chemical composition in the core. What happens to the chemical composition outside the core?
The chemical composition outside the core changes very little
When a main-sequence star runs out of hydrogen fuel in its core,
The core contracts and thus heats up
Albireo is a binary star system consisting of a bright, yellow ("gold") star and a fainter, blue star (it is the official star of the University of California, Berkeley because of its gold and blue colors). Which of the following statements about Albireo must be true?
The gold star is significantly larger than the blue star
A star that is 10 times the mass of the Sun has a luminosity 10,000 times that of the Sun. How does its lifetime compare to the 10 billion year lifetime of the Sun?
The lifetime is 1/1000 times as long.
You are asked to determine an accurate distance to the Andromeda Galaxy. Which of the following is the best technique?
The period-luminosity relation for Cepheid variable stars in Andromeda
Why do all of the planets have orbits that lie in nearly the same plane and that are in the same direction -- counterclockwise looking down on the solar system from far above the Earth's North Pole?
The planets and Sun all formed from a cloud of gas and dust that contracted as it cooled. As the cloud contracted, its spin increased and it flattened. By the time the planets formed, the cloud was a flat spinning disk.
A star is burning hydrogen to helium in its core and has 20 times the mass of the Sun. Which of the following is a true statement about this star?
The star is bluer, larger, and more luminous than the sun
Which one of the following is not influenced by the Sun's magnetic field?
The sun's blackbody spectrum
At the present time, most of the known exoplanets or exoplanet candidates have been found by using
The transit method
Two stars are shown above, with sizes and colors as indicated by the circles. Which star is more luminous? (A=small blue) (B= large orange)
There is no way to tell from this information
In a stable star such as the Sun, the gravitational forces are balanced by
Thermal pressure
Why do millisecond pulsars rotate faster than other observed neutron stars?
They are spun up by matter that spirals in to them from their companion star
The radial velocity curve for a star with an extrasolar planet is shown above. Positive velocities show when the light from the star is redshifted, and negative velocities show when the light from the star is blueshifted. At time A, in what direction is the planet moving?
Toward you
T/F Herschel's attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy's size because he was unaware of absorption by interstellar dust
True
T/F It would be easier to accurately measure the parallax of a given star from Jupiter than from Earth (though it would take longer).
True
The density of the Sun is closest to the density of
Water
A black hole is best defined as
any object that is smaller than its event horizon
The energy of the Sun is produced by
four protons and two electrons combining to form one helium nucleus
At the present time, stars in our Galaxy tend to form most readily in
giant molecular clouds in spiral arms
In 1917, our perception of the Milky Way galaxy changed when Harlow Shapley noticed
globular star clusters centered on a point far from the Sun
The energy emitted by the Sun is produced
in a small region at the very center of the Sun
The position of the Sun in the Milky Way galaxy is best described as
in the disk, slightly more than halfway out from the center
Fusion in the core of a stable massive star cannot proceed beyond iron because
iron nuclei are the most tightly bound of all nuclei, so iron fusion does not release energy
The event horizon of a black hole that is the remnant of a massive star
is the point from within which light cannot escape
If two stars are on the main sequence, and one is more luminous than the other, we can be sure that the
more luminous star is the more massive
The first extrasolar planet around a normal star was detected by observing
the "wobble" of the parent star using spectroscopy
The primary reason that massive O-type stars are not found in the Galactic halo is because they are
too short-lived to have persisted from halo formation until today
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ur moms a hoe
