ASTR Acadly Quiz (Starts at 64)

What is the mass of the object at the center of the Milky Way?

4 million solar masses

What happens to the curvature of spacetime as the mass of the object decreases?

It becomes less curved

What happens to the escape velocity from an object if you shrink it?

It increases

How can supermassive black holes at the centers of galaxies help new stars to form in that galaxy?

New stars can form when the flow of particles from a black hole accretion disk or jet compresses the material some distance away from the black hole and starts the "clumping" that leads to the formation of stars

Why do astronomers think that there are fewer quasars today than there were billions of years ago?

Quasars are seen when the supermassive black hole at the center of a galaxy has a lot of "food to eat" (stars and gas) and the amount of available foods tends to increase with time

In 1959, Pound and Rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. When two identical atomic clocks, one on the ground floor and one of the top floor, were compared

The clock on the ground floor ran a tiny bit slower

William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. Today we know this is not the case. What was a key reason that Herschel did not realize our true position in the Milky Way?

The dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the Milky Way that surrounds us.

What is Hubble's Law?

The faster a galaxy is moving, the farther away it is.

What happens to the image of the galaxy as the distance of the cluster from Earth increases?

The images get closer together

What happens to the image of the galaxy as the cluster mass increases?

The images get farther apart

For galaxies that have supermassive black holes at their centers, how do astronomers find that the mass of the host galaxy and the mass of the black hole are related?

The more massive the galaxy, the more massive the central black hole

Recently, astronomers have observed stars and other objects that orbit the center of the Milky Way Galaxy farther out than our Sun, but move around faster than the Sun. How do astronomers think such an observation can be explained?

There must be a great deal of invisible dark matter outside the orbit of the Sun whose gravitational pull explains the faster motion we see out there

Astronomers have discovered two giant "bubbles" above and below the central region of our Milky Way Galaxy that give off large amounts of gamma-rays. What do they think it one possible origin for these so called "Fermi bubbles"?

They were formed by energetic jets produced by the Milky Way's central black hole when a significant amount of matter fell in a few million years ago

Einstein suggested that a portion of the regular change (advance) in the perihelion of the planet Mercury could be explained by

a distortion in spacetime caused by the gravity of the Sun

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?

a few tenths of a second

How do astronomers know that there aren't significant amounts of dark matter within our solar system?

a lot of dark matter would affect the motions (orbits) of our spacecraft as they move through the solar system, and we see no such effect

Where is the Sun located in the Milky Way?

about 8000 light-years from the center, in the disk

Astronomers now know that surrounding the main body of our Galaxy (which our various kinds of telescopes have shown to us) and our fainter halo of stars there is

an invisible halo made of what astronomers are calling "disk matter"

What is a standard candle?

any object whose luminosity is known independently from its apparent brightness

By examining rich clusters of galaxies, such as the Coma Cluster, astronomers have discovered that spiral galaxies

are found mostly in the outer regions of such clusters, not in the middle

One of the most important observations in the history of astronomy was the one by Edwin Hubble that established that there are other galaxies, quite removed from the Milky Way. How did Hubble show this?

by observing a Cepheid variable in a nearby galaxy and using it get the distance

According to our current understanding, giant elliptical galaxies form

by the merger (or swallowing) of a number of smaller galaxies in a cluster of galaxies

According to the general theory of relativity, the presence of mass

causes curvature (or warping) of spacetime

If you are in a freely falling elevator near the top of a tall building, as the elevator falls, your weight would be:

equal to zero-you would be weightless

An astronomers needs to measure the distance of a globular cluster of stars that is part of the Milky Way Galaxy. What method should she try to use to find the distance?

find a variable star (cepheid or RR Lyrae) in the cluster

What objects did Harlow Shapley use as "signposts" to figure out the extent of the Milky Way Galaxy and the location of its center?

globular clusters

Where does the energy released by a massive black hole come from?

gravity

Where are globular clusters located in the Milky Way?

halo

Which of the following is a way that having an active galactic nuclei (AGN), with a supermassive black hole in the center, can affect the development of a galaxy?

huge energetic jets from the accretion disk can disturb and lessen star formation in the galaxy

If I want to find a sizeable collection of Population II stars in the Milky Way Galaxy, where would be a good place to look?

in the globular cluster high above the Galaxy's disk

Where did the oldest stars in the Milky Way form?

in the protogalactic cloud

Which type of galaxy does not contain a high percentage of cool interstellar gas and dust?

irregular

Which of the following is not true about the Local Group of galaxies?

it has about a thousand member galaxies

Why do galaxies collide, while stars almost never do?

stars are much further apart (compared to how big they are) than galaxies are

Elements heavier than iron can be created during

supernova explosion

If you want to write a complete "cosmic address" for yourself, including every location or structure you live in, which of the following would NOT be part of that address?

the Coma cluster

When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?

the ISS is falling around the Earth, and in free fall, things feel no weight

Where is the jet of particles coming from?

the central black hole

If a very distant galaxy looks blue overall to astronomers, from this they can conclude that

the galaxy must have a lot of young stars and thus active star formation must still be going on in it

With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that

the galaxy must have had an entire generation of stars that was born, lived, and died

What is the feature seen in the most magnified image?

the gas disk

Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighborhood galaxies?

the observation of long moving streams of stars that continue to orbit through our Galaxy's halo

What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical?

the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth

When astronomers say that the groups of galaxies are distributed isotropically, they mean that

the way galaxies are arranged in space looks the same in all directions

Astronomers can now report that active star formation was going on at a time when the universe was only 20% as old as it is today. When astronomers make such a statement, how can they know what was happening inside galaxies way back then?

they examine the spectra of galaxies (or the overall colors of galaxies) with the highest redshifts they can find

Galaxy A is moving twice as fast as Galaxy B, so Galaxy A must be

twice as far away as Galaxy B

The "great voids" that astronomers studying galaxies are finding are:

very large regions of intergalactic space, where relatively few galaxies or galaxy clusters can be found

What standard candle is useful at the greatest distances?

white dwarf supernovae

How thick is the disk of the Milky Way?

1,000 light years