Astronomy PHYS 1303 Final

If a star is 10 parsecs away, how long ago did the light we see from it tonight begins its journey toward us?

32.6 years

A graduate student is given the assignment to find stars with dusty disks around them. What kind of telescope would it be best for her to use for this purpose

A large telescope that detects infrared radiation

Astronomers today know a lot about the size and shape of the Milky Way Galaxy. Which of the following common objects most resembles the shape of our Galaxy?

CD or DVD

An astronomy class is so excited by the discovery of planets around other stars that they decide to do a library exhibit on the subject so that everyone in the school can learn about it. In this exhibit they want to pay tribute to both the astronomers of today who have done the work AND some of the scientists of the past whose work was essential to making the discoveries possible (and directly related to the techniques involved). Which of the following scientists of the past should definitely be included in the exhibit?

Christian Doppler

A graduate student in astronomy needs to measure the mass of a spiral galaxy she is studying for her PhD thesis. Which of the following observations would be important for her to make?

Determine whether or not there is evidence for a massive black hole at the galaxy's center.

If an astronomer wants to find the distance to a star that is not variable and is located too far away for parallax measurements, she can:

Find the star's luminosity class from its spectrum and read the luminosity from an H-R diagram.

Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?

K

Which of the following is a method for measuring the diameter of a star? -getting the light curve of an eclipsing binary star -comparing the color of a star seen high above our heads and then again when its near the horizon -more than one of these measuring the spectrum of a spectroscopic binary -watching the body of the Moon go across the star

More than one of the above

Your weird cousin, who is really into astronomy, decides that the return address he uses on his letters is incomplete! To his city, state, and country, he begins to add: "North America, Earth, Solar System..." If he now wants to include the name of the Galaxy's spiral-structure feature in which the Earth is located, how should his address end?

Orion Spur

Which of the following stars is a Cepheid variable?

Polaris

The first (living) star other than our own Sun found to have more than one planet orbiting it is called

Upsilon Andromedae

Astronomers now think that there is a black hole with more than 4 million times the mass of our Sun at the center of our Galaxy? Roughly how large would the event horizon of such a supermassive black hole be?

about 17 times the size of the Sun.

In an H-R diagram, where can you see the spectral type of a star (whether it is an O type star or a G type star, for example)?

along the bottom

Which of the following statements about spectroscopic binary stars is FALSE?

an analysis of the ways the lines in the spectrum change allows us to calculate the star's distance directly

Which of the following statements about the early universe (as envisioned by the standard model of cosmology) is FALSE?

at the very beginning, the energies were so great that the universe was actually contracting for a while

Imagine that a brilliant but quirky scientist in the biology department manages to put you in a deep freeze and you wake up in a million years. Which of the following statements about the sky you would see in that future time is correct?

because of proper motion, a number of the familiar constellations will look somewhat different in a million years

Why are astronomers much more interested in the luminosity of a star than its apparent brightness?

because the luminosity tells us how bright a star really is, while apparent brightness only tells us how bright it happens to look from Earth

One key difference that astronomers use to distinguish between brown dwarfs and high-mass planets is that:

brown dwarfs are able to do deuterium fusion in their cores, while planets can't

Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?

dwarf elliptical

The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called

event horizon

Where in space did the expansion of the universe begin

everywhere at once.

After the core of a massive star becomes a neutron star, the rest of the star's material

explodes as a supernova

An astronomer claims that the large redshifts of all quasars are caused by some new mechanism and not the expansion of the universe. The redshift tells us nothing, he says, about where any quasar is located. Which of the following would be a way to disprove his view of quasars?

find a number of cases where a quasar seen in a cluster of galaxies has the same redshift as all the galaxies in the cluster.

An astronomer who loved reading the Guinness Book of World Records when she was a child becomes obsessed with quasars and wants desperately to find the most distant quasar ever (the one with the largest redshift.) Where should she be looking to have the best chance of finding such a quasar?

in or near a distant cluster of galaxies that can act like a gravitational lens

Which of the following is not true about the local group of galaxies (of which the Milky Way is a member)?

it has about a thousand member galaxies

If you trace back the history of a carbon atom in your little finger through all of cosmic history, where did this atom most likely originate?

it was fused from 3 helium nuclei in the core of a red giant star long before the Sun existed.

According to our modern "bottom-up" model of the formation of large structures in the universe, the structures that formed first were about the mass of a

large globular cluster or a small galaxy

Based on many surveys of the average density of matter in the universe (regular matter and dark matter), astronomers now conclude that the average density of the universe is

less than the critical density

If we include the effects of deceleration in our calculations of the age of the universe, the age we get is:

less than the hubble time

In figuring out the evolutionary tracks on the H-R Diagram, astronomers

make model stars on a computer and then follow how their characteristics will change with time

How are globular clusters distributed in our Milky Way Galaxy?

mostly in a large spherical halo (or cloud) surrounding the flat disk of the Galaxy

Which of the following is not a way that astronomers can find how much dark matter there is in cluster of galaxies?

observe the radio waves coming from all dark matter; from the strength of the radio waves from each cluster, estimate the amount of dark matter needed to produce them

Some years after college (and after you recover from your astronomy class,) you get married and exchange gold rings with your sweetheart. What connection is there between the gold in those rings and recent observations of gravitational waves?

our new understanding is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves

Astronomers call a ball of matter that is contracting to become a star

protostar

Far away from a black hole (at the distance of another star), which of the following is a possible way to detect it?

search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

some stars can lose a lot of mass on their way to becoming white dwarfs; thus the white dwarfs could have started out as quite massive stars.

The Tully-Fisher relation (looking at rotation speeds) only works for

spiral galaxies

To establish the scale of the solar system, we need to measure the distance to one object orbiting the Sun. Venus was first used for this purpose, but in the 1930's astronomers organized an international campaign to measure the distance to:

the asteroid Eros

When an astronomer measures a color index for a star, what is she measuring? Correct Answer

the difference between how bright a star looks at two different wavelength regions

The Hubble Space Telescope has enabled astronomers to explore an active galaxy such as M87 in remarkable detail. Which of the following observations of M87 is NOT an important part of the web of evidence that shows it must have a supermassive black hole at the center?

the discovery of a gravitational lens in M87

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

On an H-R diagram of a cluster of stars, which characteristic of the diagram do astronomers use as a good indicator of the cluster's age?

the point on the main sequence where stars begin to "turn off"-- to move toward the red giant region

Some of the energy produced in the event we call Supernova 1987A was used to blow the star apart. Out of the following places that the energy of this event could go, which absorbed by far the most energy?

the production of huge numbers of neutrinos

According to Einstein's general theory of relativity, the stronger a star's gravity,

the slower time runs near it

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 we do. 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 motions we see out there

The andromeda galaxy (our nearest spiral neighbor) has a spectral lines that show a blue shift. From this, we may conclude that:

this particular nearby galaxy is moving towards us.

One important way astronomers can learn in some detail about what happens when galaxies collide is

to simulate galaxy collisions on a large computer and watch what the simulation predicts.

When neutron stars were first predicted theoretically, no scientist expected to be able to detect one of them across interstellar distances. What enabled astronomers to find neutron stars in the late 1960's?

we found strongly magnetic neutron stars whose whirling beams of energy were detected as pulsars