Exam 19: Our Galaxy

A) Orion
B) the Big Dipper
C) Leo
D) Sagittarius
E) Taurus

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D

A) a 3- to 4-million-solar-mass black hole
B) a gigantic X-ray binary system
C) a dense cluster of young,hot stars
D) an enormous collection of dark matter,which explains why we detect no light at all from the galactic center

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A) the idea that there is a lot of interstellar water vapor
B) the theory that the Milky Way is a spiral galaxy and looks like a whirlpool from above
C) the theory that hot,ionized gas blows out of the galactic center like a jet or fountain
D) the theory that hot,ionized gas blown out of the galactic disk and into the halo by superbubbles cools down and falls back into the disk
E) none of the above

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A) the dust that fills the halo of the Milky Way Galaxy
B) the middle section of the Milky Way Galaxy
C) the gas and dust that lies in between the stars in the Milky Way Galaxy
D) the name of an oracle who can channel messages from beings that live near the star called Vega

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A) 21-cm-line radio emission from atomic hydrogen.
B) visible light,showing the edges of supernova bubbles.
C) visible light,which is closest to how the night sky appears from Earth.
D) X-rays from hot gas bubbles in the disk.
E) infrared emission from interstellar dust grains.

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A) Halo stars have random orbits about the Milky Way center.
B) Halo stars are no longer being formed at the current epoch.
C) All halo stars are less massive than our Sun.
D) Halo stars are made entirely of hydrogen and helium with no heavy elements.
E) Halo stars are some of the oldest known objects in the universe.

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The bright red color is produced by an e...

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A) in the interstellar medium
B) in stars and supernovae
C) in the Big Bang,when the universe first began
D) none of the above
E) all of the above

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A) by the collapse of a gas cloud to form stars
B) by planetary nebulae from low-mass stars
C) by the winds of massive stars and supernovae
D) by collisions between galaxies
E) by the rapidly rotating magnetic fields of pulsars

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A) We see a jet of ionized gas shooting out of the bulge of our galaxy.
B) We have mapped several spiral arms of the Milky Way Galaxy.
C) We see hot gas above the disk of the galaxy and cool gas that appears to be raining down from the halo.
D) We have observed a lot of water molecules in the interstellar medium.
E) We have no evidence yet for the galactic fountain model.

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X-ray telescopes in space reveal that we are surrounded by hot,X-ray-emitting gas coming from nearby in every direction.Surrounding this hot gas lies a region of much cooler gas.This suggests that a number of supernovae have detonated within our stellar neighborhood over the last several million years and that we and all our stellar neighbors live inside a hot bubble.

A) Huge amounts of X-rays are pouring out of the center of the galaxy.
B) The center of our galaxy hosts a pulsar that is spinning so fast that it could only be a black hole.
C) We observe stars vanishing in the center of the Galaxy as they are sucked into the black hole.
D) The orbits of stars in the center of the galaxy indicate that the presence of 3- to 4-million-solar-mass object in a region no larger than our Solar System.

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A) at radio wavelengths,we see giant gas clouds threaded by powerful magnetic fields
B) at infrared wavelengths,we see a massive stellar 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

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A) It is the idea that stars in close binary systems can exchange gas with one another.
B) It is the set of nuclear reactions by which heavy elements are produced in the cores of massive stars.
C) It describes the orbits of the stars and interstellar medium around the center of the galaxy.
D) It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium.

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False

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A) They all orbit in roughly the same plane and in the same direction.
B) They have orbits randomly inclined and in different directions relative to the galactic center.
C) They follow spiral paths along the spiral arms.
D) They follow orbits that move up and down through the disk,typically taking them about 50,000 light-years above and below the disk on each orbit.

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A) They remain stationary,quite unlike disk stars that orbit the galactic center.
B) They orbit the galactic center with many different inclinations,while disk stars all orbit in nearly the same plane.
C) Halo stars explode as supernovae much more frequently than disk stars.
D) They orbit the center of the galaxy at much lower speeds than disk star.

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