Astronomy 100 Final
In which phase of a star's life will nuclear fusion reactions in the central core convert helium into carbon?
During and immediately after the 1st red giant or supergiant phase
The rotation of the Sun is
fastest at the equator, slower at mid-latitudes, and slowest near the poles.
All stars on the main sequence
generate energy by hydrogen fusion in their centers
What kinds of objects lie in the halo of our galaxy?
globular clusters
The temperature of the corona of the Sun is
very high-about 10^6 K
You observe a star cluster with a main-sequence turn-off point at spectral type G2 (same spectral type of the Sun). What is the age of this star cluster?
10 billion years
How long is a day on Saturn?
10.6 hours
A star with a spectral type B with a mass 10 times that of the sun lives approximately how long on the main sequence?
100 million years
What is the source of the heavy elements on the Earth and in our own bodies? a. Explosive nucleosynthesis during supernova explosions of massive stars b. Cosmic ray interactions with hydrogen and helium nuclei in interstellar clouds c. Nuclear reactions during the Big Bang d. Thermonuclear fusion reactions in the cores of massive stars before the supernova phase.
A. Explosive nucleosynthesis during supernova explosions of massive stars
Why do Saturn's inner rings orbit faster than the outer rings?
Because Kepler's laws says if you orbit closer you move faster
What causes the granular appearance of the sun?
Convective motion under the solar surface
Which of the following statements about black holes is NOT true? a. If you fell into a supermassive black hole you would experience time to be running normally as you plunged into the event horizon. b. If we watch a clock fall into a black hole, we will see it tick slower and slower as it falls towards the black hole. c. The event horizon of a black hole represents a boundary from which nothing can escape d. If the Sun magically disappeared and was replaced by a black hole of the same mass, the Earth would soon be sucked into the black hole.
D. If the sun magically disappeared
We can tell that some stars are relatively close to us in the sky because a. they appear extremely bright b. the are occasionally occulted or eclipsed by the moon. c. the light from these stars shows a very small blue shift caused by the universal expansion of the universe d. they appear to move periodically back and forth against the background stars because of Earth's movement around the Sun
D. They appear to move periodically back and forth against the background stars because of Earth's movement around the Sun
T or F: No visible light can escape a black hole, but things such as gamma rays, X-rays, and neutrinos can escape.
False
True or False: A lenticular galaxy is another name for an elongated elliptical galaxy
False
True or False: A pulsar is a white dwarf that has an oscillating luminosity
False
True or False: All heavy elements are made during a supernova explosion
False
True or False: Energy from the core of the Sun first travels slowly through the convection zone and then much faster through the radiation zone
False
True or False: Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure
False
True or False: Interstellar dust makes a star look bluer than it really is
False
True or False: It is impossible for a star to have a negative apparent magnitude
False
True or False: Main sequence fitting is the process by which scientists determine a star's temperature by carefully measuring its absorption spectrum
False
True or False: Red giant stars are less luminous than young white dwarf stars because their surface temperatures are much cooler
False
True or False: The helium fusion process works by fusing two helium nuclei into 1 beryllium nucleus
False
True or False: The smaller the value of Hubble's Constant, the more rapid the expansion of the universe and the smaller (and hence younger) our estimate for the age of the universe.
False
True or False: Two stars have the same luminosity. Star X is spectral type F, while star Y is spectral type K. Star X must be larger than Star Y
False
True or false: Elements heavier than helium cannot be produced by ordinary nuclear fusion reactions because fusion reactions for elements heavier than helium require energy rather than release energy
False
True or false: The larger the apparent magnitude of a star, the brighter it appears to the unaided eye
False
What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from sever collisions among smaller clouds?
Halo stars differ in age and heavy-element content, but these variations do not seem to depend on the stars' distance from the galactic center
The nuclei of which chemical elements are converted to other nuclei in order to produce the requisite thermonuclear energy that heats teh Sun?
Hydrogen is converted to Helium
Why does the big storm at Saturn's south pole allow scientists to see deep into Saturn's atmosphere?
I has an eyewall, similar to a hurricane on earth.
Where does most star formation occur in the Milky Way today?
In the spiral arms
A sequence of thermonuclear fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon, oxygen, etc. into heavier nuclei and also generate excess energy, up to a limit beyond which no further energy-producing reactions can occur. The element that is produced when this limit is reached is
Iron
What amazing discovery was made on Enceladus in 2005?
It has "jets" and similar activity, one of the smallest objects to have that
Why is Enceladus a strong candidate location for extraterrestrial life?
It has water in jets and ice
If star A is closer to us than star B, then Star A's parallax angle is _________.
Larger than that of Star B
The oldest star cluster is the one where the brightest main-sequence stars are what type?
M stars
What is the relationship between the mass of a protostar and the time needed for it to reach the main sequence after it forms inside an interstellar cloud?
More massive protostars reach the main sequence in a shorter time than less massive protostars
Is Saturn the only planet with rings?
No
What is the only moon in the Solar System to have a thick atmosphere?
Saturn's moon, Titan
True or false: the photosphere is the coolest region of the Sun
True
Star X has an apparent magnitude of 3, and star Y has an apparent magnitude of 13. How do they compare in observed brightness?
Star X is 10,000 times brighter than Star Y
Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?
The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form
Why do elliptical galaxies appear yellow or red?
They have very little dust or cool gas, and thus have little ongoing star formation and contain no hot, young blue stars
Which part of the HR diagram is occupied by protostars?
To the right of the main sequence
T or F: Shapley used the distribution of globular clusters in our galaxy to determine that the Sun was not at the Center of the Milky Way
True
True or False: Brown dwarfs, white dwarfs, and neutron stars are all kept from collapsing by degeneracy pressure
True
True or False: Elliptical galaxies are more likely to be found in clusters than spiral galaxies
True
True or False: Gas and dust must have a very low temperature in order to begin to condense into a protostar
True
True or False: Most of the current star formation in the Milky Way occurs in the spiral arms.
True
True or False: Our Sun will end its life in a planetary nebula and become a white dwarf
True
True or False: The average number of sunspots visible on the Sun's surface rises and falls over a period of about 11 years.
True
True or False: The corona and chromosphere are hotter than the photosphere
True
True or False: The orbital speeds in the outer regions of galaxies indicate a large amount of dark matter lies beyond their visible regions.
True
True or False: The sun rotates more quickly at the equator than at the poles
True
True or false: A pulsar is a rapidly rotating neutron star
True
True or false: All main sequence stars of spectral type G have approximately the same mass
True
True or false: If the distance between us and a star is doubled, its apparent brightness will decrease by a factor of four
True
True or false: the more massive the star, the faster it will evolve through its life
True
On a HR diagram, where would you find stars that are cool and luminous?
Upper Right
What are Saturn's rings made of?
Water ice with traces of another material such as silicates
How thick are Saturn's rings? a. .05 m b. 50 m c. 50 km d. 50,000 km
b. 50 m
Which of the following hypothetical observations would contradict our theories about the formation and evolution of white dwarfs? a. a white dwarf with a mass 1.8 times the Sun b. a white dwarf with a surface temperature of 6000 K c. a white dwarf at the center of a planetary nebula d. a white dwarf with a main sequence companion star that has a mass of 1.8 solar masses
a. a white dwarf with a mass of 1.8 times the Sun
Among the following locations in the universe, where would you expect to find a neutron star? a. at the center of a supernova remnant b. at the core of a red giant c. at the center of a galaxy d. at the center of a white dwarf
a. at the center of a supernova remnant
Which of the following is not evidence for dark matter? a. the expansion of the universe b. the flat rotation curves of spiral galaxies c. Doppler measurements of galactic motion within galaxy clusters d. Gravitational lensing around galaxy clusters
a. the expansion of the universe
Imagine a big ocean of water, larger than the planet Saturn, would Saturn float in it? a. yes, because it is less dense than water b. yes, because its angular momentum would prevent it from sinking c. No, Saturn is so cold that the water would freeze into an ice shell and it would sink. d. No the rocks inside Saturn are denser than water and thus the entire planet would sink
a. yes, because it is less dense than water
Compared with stars in the disk, orbits of stars in the halo
are elliptical, with random orientations
In a uniformly expanding universe, which statement best describes the situation as viewed from an observer in Galaxy C (not the Milky Way Galaxy)? a. Galaxy C observer sees all galaxies moving away from the Milky Way. b. Galaxy C observer sees all other galaxies moving away from Galaxy C c. Galaxy C observer sees some galaxies moving away, some moving toward Galaxy C d. Galaxy C observer sees all galaxies moving toward the Milky Way
b. Observer sees all galaxies moving away
Which of the following characterizes the early stages of a red giant? a. a large red protostar in the "upper right" part of the HR diagram b. a large, red star that is expanding its atmosphere while its helium core collapses c. a large red star that is burning helium in a shell around its carbon core d. a large red star that is burning hydrogen into helium in its core
b. a large red star that is expanding its atmosphere while its helium core collapses
The distribution of the dark matter in a spiral galaxy is a. approximately spherical and about the same size as the galaxy halo b. approximately spherical and about ten times the size of the galaxy halo c. flattened in a disk but about ten times larger than the stellar disk d. predominantly concentrated in the spiral arms
b. approximately spherical and about ten times the size of the galaxy halo
Which of the following will a high mass star (~25 times the mass of the sun) NOT do at the end of its life? a. Convert silicon to Iron in its core b. Eject its outer layers and become a white dwarf c. Emit copious amounts of neutrinos d. Eject its outer layers and become a neutron star
b. become a white dwarf
Which of the following processes does NOT lead to star formation? a. compression waves passing through interstellar clouds in the arms of spiral galaxy b. compression of a hot interstellar gas cloud by its own gravity c. compression of a cold part of a large interstellar cloud by another part which contains a group of hot, young, massive stars d. compression of a cold interstellar gas-and-dust cloud by the shock wave from a nearby supernova explosion
b. compression of a hot interstellar gas cloud by its own gravity
Saturn appears as an "oblate spheriod" because of its a. low temperature b. high spin rate c. low density d. rings
b. high spin rate
Instead of water, Titan's lakes and rivers are apparently made out of _____. a. ammonia b. methane and ethane. c. nitrogen d. freon
b. methane and ethane
Which of the following descriptions does NOT represent a property of neutron stars? a. rotation rates from one to 30 times each second b. strong gravitational fields but weak magnetic fields. c. composed mostly of neutrons and protons d. emitters of relatively narrow beams of radio energy and other electromagnetic radiation
b. strong gravitational fields but weak magnetic fields
The luminosity of a star is a. its apparent brightness if it were a distance of 1 pc from Earth b. the total power it emits into all of space c. another name for its color or surface temperature d. its brightness as seen by people on Earth
b. the total power it emits into all of space
Our Sun will end its life by becoming a. pulsar b. white dwarf c. black hole d. molecular cloud
b. white dwarf
How can we see through the interstellar medium?
by observing at wavelengths (high-energy X-rays and long wavelength radio waves) that are not absorbed by interstellar dust
How do astronomers measure the masses of stars?
by observing the motion of two stars in a binary star system
The energy produced in the central core of the Sun is transported to the surface
by radiation in the layers just outside the central core and by convection in the outer layers
Which of the following does NOT accurately describe what we observe toward the Galactic Center? a. At radio wavelengths, we see giant gas clouds threaded by powerful magnetic fields b. At infrared wavelengths, we see a massive star cluster. c. At optical wavelengths, we see a cluster of old, red stars. d. At X-rays, we see faint emission from an accretion disk around a black hole?
c. At optical wavelengths, we see a cluster of old, red stars
Which of the following is closest to the size of a neutron star? a. Jupiter b. Earth c. a city d. a football stadium e. a basketball
c. a city
A planetary nebula is created: a. in seconds, during the helium flash in a low-mass star b. in hours or less, during the explosion of a massive star c. slowly, over thousands of years, due to thermal pulses in a low-mass star d. over several hundred years, during the tidal destruction of orbiting planets.
c. slowly, over thousands of years
Suppose that we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest? a. the reddest b. the bluest c. the farthest d. the closest e. the one that appears smallest
c. the one that is farthest away
The spectral class of the Sun is G2 and the star Enif is K2. From this information we know that the Surface of Enif is
cooler than the Sun
What is the most accurate way to determine the distance to a nearby galaxy? a. radar ranging. b stellar paradox. c. main sequence fitting d. Cepheid Variables e. Hubbles law
d. Cepheid Variables
Two stars, one classified A8 and the other G4, have the same apparent magnitude. We know that a. both stars are the same distance from earth b. the A8 star is much smaller than the G4 star c. the A8 star is closer to the Earth than the G4 star d. the A8 star is farther from the Earth than the G4 star
d. the A8 star is farther from the Earth than the G4 star
Electron degeneracy occurs when
electrons inside a star resist being pushed closer together than a certain limit
Spectral class of stars into the lettered categories, OBAFGK and M is carried out by
examining the absorption lines from hydrogen and other elements that are present in a star's spectrum
Why does stellar main-sequence lifetime decrease with increasing stellar mass?
higher core temperatures cause fusion to proceed much more rapidly
One major feature that distinguishes a sunspot from other regions on the Sun is
its very powerful magnetic field
What is a prominence on the Sun?
large loop of gas supported by magnetic fields
What is the solar wind?
material from the corona, accelerated out into space
The process that produces energy inside a white dwarf is
nonexistent; a white dwarf is slowly cooling off
The Scwarzchild radius of a black hole depends on_____.
only the mass of the black hole
The apparent reddening of light from stars after its passage through the interstellar medium (ISM) is caused by
preferential scattering of blue starlight by fine dust grains in the ISM
Compared to a star in the middle of the diagram, a star in the lower left part of the Hertzsprung-Russell diagram is
smaller
The spectrum of an ordinary main-sequence star is a
smooth continuum of color, with no sharp emission or absorption lines
When observed through a set of photometric filters, the brightness of a distant star is seen to be brightest through the ultraviolet filter, less bright through the blue filter, and faintest through the yellow filter. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?
the star has a very high surface temperature
What heats up Enceladus?
tidal heating