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Flashcards in Final Deck (42):

An astronaut who fell into a black hole would be stretched because,

the force of gravity increases quickly over short distances.


If the Sun collapsed to a black hole today, how would it affect the Earth?

It would be dark
(no effect on orbit and nobody would be 'sucked' off Earth)


The formation of the Milky Way's ______ depended on the presence of gas.



Halo objects orbit the center of the Milky Way

in random orientations and directions


The Milky Way's ______ composed of stars (and gas and dust) in randomly oriented orbits.

halo and bulge are


Most of the mass in the Milky Way is,

dark matter


A DVD's rotation curve (velocity vs. radius) graph,

increases as radius increases


A disk galaxy's rotation curve,

is relatively constant as radius increases.


The Milky Way's rotation curve provides evidence of dark matter because

-additional, invisible matter is required to keep the rotation speed relatively constant.

-the rotation curve extends far beyond the Milky Way's disk


You've found a dwarf galaxy that may be orbiting the Andromeda Galaxy. Refer back to your text to determine which of the following steps on the distance ladder could be used to determine its distance, assuming it is nearby Andromeda. (check all that apply

-White dwarf (Type 1a supernova)
-cepheid variable star


Which object can not be used to measure distances?

A massive star (type II) supernova


An astronomer has found an object in a distant galaxy that appeared suddenly, grew in brightness for a short time, and then faded from view. The light curve of this object can be used to determine,

what kind of object it is, and if it can used to measure distance at all.


An observer at a UW observatory detects a white-dwarf supernova in a distant galaxy right now. An observer looking at the same location right now from inside that distant galaxy, could observe,

supernova remnant, but nothing else.


Imagine three widely separated galaxies arranged in a line. If you are in the first galaxy (galaxy number 1) you observe that both the middle (number 2) and the right (number 3) galaxies are moving away from you.

If you asked observers in galaxy number 3 how galaxy number 2 appeared to move, what would they say?

Galaxy 2 is moving away from Galaxy 3


Astronomers observe two galaxies, A and B. Galaxy A has a recessional velocity of 1000 km/s, while galaxy B has a recessional velocity of 2000 km/s. This means that:

Galaxy B is twice as far away as galaxy A.


A star that is moving toward us will have,

its spectral lines shifted to shorter wavelengths.


Which is likely to have the largest redshift?

a galaxy (not a star)


Which type of galaxies appear to have many young stars?

disk galaxies


Do the disk galaxies also contain old stars?



Which type of galaxies are more likely to show evidence of dust?

disk galaxies


If a galaxy is experiencing active star formation, it must contain

cool, dense gas


Which type of galaxies have cool, dense gas available for star formation?

disk galaxies


Which type of galaxy shows evidence of significant numbers of O-stars and M-stars?

disk galaxies


Which type of galaxy is likely to contain many M-stars but few O-stars?

elliptical galaxies


Consider the discussion among three students about a galaxy that appears red

it’s just that blue stars don’t last very long.
-the blue stars that may have been there in the past have already evolved into red giants, so the galaxy looks red due to the light from all the red giants


velocity equation

v = cz

z = redshift
c = speed of light (3.0 x 10^5 km/sec)


Galaxy vs star redshifts

Galaxies have much larger redshifts than stars


Spectral lines of galaxies redshift

shifted toward longer wavelengths
= moving away from us


Observations of which of the following objects revealed the accelerated expansion of the universe?



It has been shown from recent observations that the universe is not only expanding but that the expansion is accelerating! Which of the following is believed to be responsible for the acceleration?

dark energy


Over time the universe has become

bigger, cooler, and less dense


Which of the following are moving apart due to the expansion of the universe?

two widely separated galaxies


How is the motion of galaxies in our local group different from what we observe for distant galaxies?

some are moving toward us


The center of the Universe:

may not even exist


Why aren't the Milky Way, the Solar System, and even the Earth ripped apart due to the expansion of the Universe?

The expansion of the Universe only occurs on the largest scales, and can only carry apart objects that aren't bound to each other.


Observations of the Cosmic Microwave Background Radiation have given us the following current composition of the universe: 5% Normal Matter, 23% Dark Matter, and 72% Dark Energy. How was the composition of the early universe different?

there was less dark energy


Which of the following will determine if the universe will expand forever?

-The amount of dark matter in the universe.

-The amount of dark energy in the universe.

-The amount of normal matter in the universe.


Astronomers measure a star's color by,

comparing its brightness through two different filters.


Consider the following four stars, their g magnitudes, and their g-r colors:

Star g g-r
A 12. -0.4
B 15. 1.3
C 14. 1.2
D 16. 0.2

Which is brightest in the sky?



Consider the following four stars, their g magnitudes, and their g-r colors:

Star g g-r
A 12 -0.4
B 15 1.3
C 14 1.2
D 16 0.2

Which is bluest?



Consider the following four stars, their g magnitudes, and their g-r colors:

Star g g-r
A 12 -0.4
B 15 1.3
C 14 1.2
D 16 0.2

Which is the least luminous?

need more information to tell


The horizontal axis of a spectrum in astronomy is,