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CH 23 HW
Most of the bright stars in our Galaxy are located in the Galactic
disk. |
center. |
bulge. |
halo. |
Globular clusters are found mainly
in the Galactic center. |
in the Galactic disk. |
in spiral arms. |
in the Galactic halo. |
Shapley measured the distances to globular clusters by using
comparison of the absolute and apparent magnitudes of variable stars. |
trigonometric parallax. |
spectroscopic parallax. |
radar ranging. |
The first portion of the galaxy to form was the halo.
A tightly packed group of a few hundred thousand very old stars is a globular cluster.
A spiral arm stands out in a photo of a galaxy because it shines brightly with light from massive young stars and glowing clouds of gas and dust.
Our Milky Way galaxy is a spiral galaxy
Stars orbiting in the bulge near the galaxy's center can have orbits highly inclined to the galactic plane.
Suppose that astronomers have discovered a new variable star that is either a Cepheid or an RR Lyrae. Which of the following properties of the star would NOT be helpful to use in determining which type of star it is?
Luminosity |
Distance |
Pulsation period |
The first stars that formed in the Milky Way now
orbit closest to the Galactic center. |
orbit in the Galactic plane. |
orbit in the same direction as the Milky Way spins. |
have random orbits in the halo. |
Where are large dust clouds predominantly located in the galaxy M51?
distributed evenly throughout the galaxy |
within or on the edges of the spiral arms |
in the central bulge of the galaxy |
in the wide spaces between the spiral arms |
Where are the ionization nebulae predominantly located in the galaxy M51?
distributed evenly throughout the galaxy |
within or on the edges of the spiral arms of the galaxy |
in the central bulge of the galaxy |
in the wide spaces between the spiral arms |
Why are the ionization nebulae so bright?
They are the remains of stars that have died in supernova explosions. |
They become very hot because of collisions with dust clouds. |
They are always located very near a galaxy’s hot core. |
They are regions where gas is ionized by hot, young stars. |
A telescope searching for newly formed stars would make the most discoveries if it were pointed
between spiral arms. |
directly away from the Galactic center. |
perpendicular to the Galactic disk. |
within a spiral arm. |
Most of the mass of the Milky Way exists in the form of
dark matter. |
dust. |
gas. |
stars. |
“Galaxy Rotation Curve” says
there is no matter beyond 15 kpc from the Galactic center. |
the Galaxy rotates like a solid body. |
far from the center, the Galaxy rotates more rapidly than expected based on the light we see. |
far from the center, the Galaxy rotates more slowly than expected based on the light we see. |
When we look at the orbital speeds of stars in the Milky Way, we at first expected
Stars far from the center should orbit at the same speed as stars closer to the center. |
Stars far from the center should orbit more slowly than stars closer to the center. |
Stars far from the center should orbit more quickly than stars closer to the center. |
There is evidence that a supermassive black hole is at the center of the Milky Way based upon
Our motion directly towards the center of the Milky Way. |
The bright source of optical light we can see from the center. |
The orbits of stars very close to the center. |
Infrared observations of the galactic center reveal broadened infrared spectral lines, indicating fast moving gas. There must be large central mass to be causing such rapid motion.
Radio and x-ray observations also reveal rapid motions in the center, and that the cause of all the motion appears to be a very compact object.
The speed of the moving material is such that an object many orders of magnitude more massive than a star, or cluster of stars, is required for such orbital motion. Such this object is best explained by a supermassive black hole.
The main evidence for a black hole at the Galactic center is that
the Galaxy rotates faster than astronomers expect. |
stars near the center are disappearing. |
stars near the center are orbiting some unseen object. |
no stars can be seen in the vicinity of the center. |
In which of the basic regions of the galaxy is the Sun located?
galactic disk |
galactic center |
galactic halo |
galactic bulge |
Why are infrared and radio telescopes the instruments of choice for studying the galactic center?
The galactic center radiates energy only in the radio frequency and infrared bands. |
Dust in the plane of the Milky Way obscures observations at other wavelengths. |
Radio and infrared telescopes are bigger than optical ones and can see farther. |
There are more radio and infrared telescopes than optical ones in the world. |
Radio and infrared telescopes are cheaper to build and operate than optical ones.  |
NoteStudied by 10 peopleNoteStudied by 41 peopleNoteStudied by 173 peopleNoteStudied by 11 peopleNoteStudied by 4 peopleNoteStudied by 4 people