astro test 3 mc

Most of the mass of the Milky Way seems to exist in the form of:

the black hole in the Galactic Center.

Which of the rotation curves best represent the orbital speeds of planets in the Solar System?

the c

All globular clusters in our Milky Way are about how old?

around ten billion years old

A star (no matter what its mass) spends most of its life:

as a main sequence star.

If the Sun were replaced by a one solar mass black hole:

we would still orbit it in a period of one year.

In age, Population I stars are typically much ________ than those of Population II.

younger

What would happen if more mass was added to a 1.4 solar mass neutron star?

It could eventually become a black hole, via a hypernova explosion.

What effect do even thin clouds of dust have on light passing through them?

It dims and reddens the light of all more distant stars.

Which of the following can actually escape from inside a black hole's event horizon?

None of these

A galaxy is at a distance of one billion light years. Which of the following is true?

We see the galaxy the way it was one billion years ago.

Pre-21.4: The most direct route between San Diego, California, and Caribou, Maine, is about 5,300 kilometers (km). If your average speed is 110 kilometers per hour (km/h), how many hours will you actually spend driving? a. 24 hours b. 48 hours c. 26 hours d. Not enough information is given to answer this question

avg speed= distance moved/ time b

Which of these is the likely progenitor of a type II supernova?

an evolved red giant which is just starting to make silicon in its core

Post-21.5: What if the date of April 16, 1996, should have actually been March 16, 1996. How would the calculated speeds of the material compare? a. The revised speed would be the same. b. The revised speed would be much greater. c. The revised speed would be a bit slower.

b

Post-23.5: Gas and dust particles in a disk surrounding a black hole often collide with other particles and in the process lose energy and slow down. The most likely outcome if these particles lose speed will be a. no change because the particles will still be part of the disk. b. that they will curve down toward the black hole and fall in. c. that they will curve toward the black hole but pass it and continue on through space.

b

Pre-25.4: Which star is the closest to us? choice M m a 0 10 b 0 8 c 0 13 a b c

b

The graph of the orbital speed of stars throughout the disk of the Milky Way Galaxy implies the existence of a) the distribution of globular clusters. b) dark matter. c) spiral arms. d) gas and dust. e) dark energy

b

Neutron stars do NOT have:

rotation periods comparable to the Sun's.

Neutrinos flee the Sun in

seconds

Most of the galaxies in the Local Group are:

small ellipticals like the companions to M31 in Andromeda.

The elements heavier than iron are created in....

supernova

What two observations allow us to calculate the Galaxy's mass?

the Sun's orbital velocity and its distance from the Galactic Center

The supernova that formed M-1, the Crab Nebula, was observed in

1054 AD by Chinese and Middle Eastern astronomers.

A supernova that occurred 30,000 years ago in a galaxy 100,000 light years away will be observed on Earth:

70,000 years from now.

Interstellar gas is composed of:

90% hydrogen, 9% helium by weight.

Pre-23.4: Two people with different masses are racing on bumper cars. They are traveling at the same speed. If the same force is applied to each person as they turn, which one will have the larger curving path? a. the heavier one b. the lighter one c. They will both follow the same curve.

A

All of the following are clusters of galaxies EXCEPT:

Andromeda

Neutrinos are proof that fusion is happening at the core of the Sun but how are neutrinos detected?

Astronomers detect neutrinos with large tanks of extremely pure fluid deep underground.

Pre-25.4: Which star is the brightest? choice M m a 0 10 b 0 8 c 0 13 a b c

B

What does the capital B in the bottom of the "tuning fork" stand for?

Bar

Compared to our Sun, a typical white dwarf has

Correct Answer about the same mass and a million times higher density.

During the hydrogen shell burning phase in a Red Giant:

Correct Answer the star grows more luminous.

The order of evolutionary stages of a star like the Sun would be Main Sequence, giant, planetary nebula, and finally:

Correct Answer white dwarf.

Neutron stars and black holes are formed by:

Correct Answer type II supernovae.

In Hubble's classification, which type of galaxy has no stellar disk and no gas or dust?

E0

Galaxies only come in Spiral or Elliptical types.

False There are also Irregulars, like the Large Magellanic Cloud

In structure, our Milky Way is most similar to:

M-31, the Andromeda Galaxy.

What compelling evidence links pulsars to neutron stars?

Only a small, very dense source could rotate that rapidly without flying apart.

The location of the Galactic Center was first found by Harlow Shapley with:

RR Lyrae variables in the globular clusters.

The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ________ according to Hubble.

SBb

You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified an:

Sa.

Which of the following statements is FALSE about binary star systems?

The masses of each star in a binary system cannot be found.

What is the primary reason why are the arms of spiral galaxies typically blue in color?

Stars are forming in the spiral arms so there are high mass, hot, blue stars in the arms.

Which of the following statements is FALSE about the Milky Way dark matter?

The dark matter comes from the super massive black hole at the center of the galaxy.

What would happen if mass is added to a 1.4 solar mass white dwarf?

The star would erupt as a type I supernova.

There are red and blue stars in Spiral and Elliptical galaxies

True

Post-21.3: Observationally, what is the difference between a neutron star and a pulsar? a. Not all neutron stars are beaming radiation in our direction and pulsing. b. Neutron stars always rotate much faster than pulsars. c. Neutron stars usually rotate much slower than pulsars. d. Pulsars are much larger than neutron stars and thus give off more light.

a

Post-23.1: Black hole A has a mass that is twice the mass of black hole B. From this information, you can say that the event horizon of black hole A is a. larger than the event horizon of black hole B. b. smaller than the event horizon of black hole B. c. the same size as the event horizon of black hole B.

a

Post-23.4: Suppose that light approaches a black hole so that its closest approach is just outside the event horizon. This light will curve a. toward the black hole but pass it and continue on through space. b. away from the black hole and continue on through space. c. down toward the black hole and fall in. d. around the black hole on a circular orbit.

a

Post-25.1: What aspect about globular clusters and our observations of the distances to them modified our view of the Milky Way Galaxy and our place in it? a. They all orbit the center of the galaxy, and the center of their distribution is not where we are. b. Some of the globular clusters are very far away and must belong to the Andromeda Galaxy. c. We found out that there are hundreds of globular clusters hidden by columns of dust. d. The most distant globular clusters are metal-rich and so must have originated in the disk.

a

Post-25.4: An observer far outside our galaxy would best describe our galaxy and the Sun's position in it as a a. disk of stars with our Solar System toward the edge. b. disk of stars centered on our Solar System. c. disk of stars with our Solar System located in the bulge. d. sphere of stars centered on our Solar System.

a

Pre-21.2: The correct ordering of the electromagnetic spectrum from highest-energy radiation to lowest is a. gamma rays, X-rays, ultraviolet, visible (optical), infrared, radio b. X-rays, visible (optical), infrared, radio, gamma rays, ultraviolet c. radio, infrared, visible (optical), ultraviolet, X- rays, gamma rays

a

Pre-21.3: True or False: How we name and categorize celestial objects may often depend simply on what we are seeing from our point of view. (A terrestrial example would be first seeing a train coming directly at us on the track versus waiting in our car behind a barrier at a train crossing.) a. true b. false

a

Pre-23.2: The force that you feel as you go around a corner is required to keep you on the seat as you turn. In this case, the force comes from friction. What happens if you are wearing slippery pants, and the friction force is too small to turn you around a curve? a. You continue to travel in a straight line. b. You travel around the curve on a larger circular path. c. You travel around the curve on a smaller circular path

a

Pre-23.3: Identical twins with identical masses are racing in bumper cars. One twin is traveling faster than the other as they turn a corner. If the same force is applied to each twin as they turn, which twin will have the larger curving path? a. the faster one b. the slower one c. They will both follow the same curve.

a

Which of these does NOT exist?

a 6.8 solar mass neutron star

A hypernova creates:

a black hole.

Collisions between galaxies are thought to:

be commonplace.

Group Problem Pre-activity Question 1) In a spiral galaxy, the orbital speeds of stars far from the galaxy's center _______ as the distance from the center increases. a) increase b) decrease c) are approximately the same d) The answer changes depending on the galaxy.

c

Post-21.2: Which one of the following choices correctly explains a reason we need space telescopes. a. Space telescopes are high above Earth and thus are closer to celestial objects. b. Putting telescopes into space is cheaper than building observatories on the ground. c. Space telescopes are needed to observe portions of the spectrum blocked by Earth's atmosphere. d. All of these are valid reasons for needing space telescopes

c

Post-23.3: Suppose that light approaches a black hole so that its closest approach is just inside the event horizon. This light will curve a. toward the black hole but pass it and continue on through space. b. away from the black hole and continue on through space. c. down toward the black hole and fall in. d. around the black hole on a circular orbit.

c

Pre-21.1: Which one of the following pairs of regions of the electromagnetic spectrum is partially or totally blocked by Earth's atmosphere? a. visible, radio b. infrared, radio c. X-ray, infrared d. visible, infrared

c

Pre-21.5: Energy produced in the proton-proton cycle at the core of the Sun is in the form of gamma rays, and yet most of the radiation the Sun gives off at its surface is in the visible part of the spectrum. What has happened to the energy of the photons? a. The photons lose energy through interactions with electrons. b. An ultraviolet photon absorbed by a hydrogen atom may emit a series of photons having lower energies. c. Both of these answers involve similar interactions.

c

Pre-25.4: Which star is the dimmest? choice M m a 0 10 b 0 8 c 0 13 a b c

c

The idea of dark matter is provided to explain which one of the following? a) the location and shape of the arms in the disk of spiral galaxies b) the location of the maximum in the distribution of globular clusters of stars in the halo of the galaxy c) the nearly uniform rotation speeds of objects in the Milky Way Galaxy d) that a spiral density wave moves through the disk of spiral galaxies triggering star formation e) that spiral galaxies slowly evolve into elliptical galaxies

c

Which of the rotation curves best represent the orbital speeds of stars in the Milky Way Galaxy would have if there were no dark matter in the galaxy?

c

Post-21.4: If the radius of a neutron star is about 10 km and its mass roughly 1.4 times that of the Sun, which one of these statements is true? a. The force of gravity on the surface of a neutron star is roughly 7,000 times that of the Sun. b. The neutron star's much smaller radius makes its surface gravity smaller than that of the Sun. c. The surface gravity of the neutron star is many billions of times greater than that of the Sun. d. A neutron star's radius is about the size of a city, so its surface gravity is comparable to Earth's.

c Fg= G(m1)(m2)/(r^2)

Charles Messier mapped the night sky and identified many objects now known to be emission nebulae in his search for objects that might be confused with:

comets

Based on galactic rotation curves and cluster dynamics, we think dark matter

comprises over 90% of the entire mass of the universe.

Electrons spiraling in strong magnetic fields at extremely high speeds radiate at a. infrared wavelengths b. optical wavelengths c. ultraviolet wavelengths d. X-ray wavelengths

d

How do we know where we are in the disk of the Milky Way Galaxy? a) by measuring the redshift of stars in the galaxy b) by determining how much dark matter exists in the galaxy c) by measuring the size and speed of the spiral density wave in the disk d) by determining the distribution of globular clusters in the halo

d

Post-23.2: Light approaches a black hole so that its closest approach is precisely at the event horizon. This light will curve a. toward the black hole but pass it and continue on through space. b. away from the black hole and continue on through space. c. down toward the black hole and fall in. d. around the black hole on a circular orbit

d

Post-25.2: Astronomers need to measure the distances to the stars in the Milky Way globular clusters. What method should they use to find the distances? a. Measure the trigonometric parallaxes of all the globular clusters during the course of a year. b. Count the number of O- and B-type stars and remnants of supernovae in the clusters. c. Look for flickering X-rays coming from black holes in binary systems in the clusters. d. Find RR Lyrae variable stars in the clusters and measure their mean apparent magnitudes.

d

Pre-23.1: Suppose that you are riding on a ride in which you sit on top of a little cart and ride along a twisty downhill track. At which speed will you feel the strongest acceleration as you go around a corner? a.15 mph b.25 mph c.35 mph d.45 mph

d

Pre-25.1: Using this polar graph, state which labeled dot is at 147.5°, nine rings from center. a. A b. B c. C d. D e. E

d

Pre-25.7: We use the distance equation d=10[(m-M+5)/5] to find distances to celestial objects when we know their apparent magnitudes, m, and absolute magnitudes, M. Let m = 6 and M = -2 and find the corresponding distance in parsecs (pc). What is the correct distance? a. 100,000 pc (105 pc) b. 1,000,000,000 pc (109 pc) c. 26 pc d. 398 pc (102.6 pc)

d

Which of the following correctly lists objects from largest to smallest? a) Nebula, Galaxy, Local Group, Star b) Globular Cluster, Local Group, Galaxy c) Galaxy, Local Group, Nebula, Star d) Local Group, Galaxy, Globular Cluster, Star

d

Why are globular clusters ideal for determining the size of the Milky Way and our location in the galaxy? a. Most lie above the plane of the Milky Way and so are not very obscured by dust. b. Most globular clusters have a large number of RR Lyrae variable stars. c. The clusters must orbit the center of the galaxy. d. All of these answers are correct.

d

Which of these objects have NOT been found in the Galactic Halo?

emission nebulae

The distance between adjacent galaxies in a typical cluster is about ________ times the size of a typical galaxy.

five or less

In the formation of our Galaxy, the ________ formed first.

globular clusters

Which of the following elements contained in your body is NOT formed in the cores of stars during thermonuclear fusion?

hydrogen

When a star's inward gravity and outward pressure are balanced, the star is said to be:

in hydrostatic equilibrium

Which is the correct description of the Sun's location within the Milky Way?

in the disk and about one-half a galactic radius from the center

The largest known black holes:

lie in the cores of the most massive galaxies.

A method for identifying a black hole is to:

look for their effects on nearby companions.

In a neutron star, the core is:

made of compressed neutrons in contact with each other.

What produces a type-I supernova?

mass transfer onto a white dwarf pushing it over 1.4 solar masses

Which is characteristic of globular star clusters?

old age and hundreds of thousands of stars, only about 30 ly wide

Which is used observationally to determine the age of a star cluster?

the luminosity of the main sequence turn-off point

What characteristic of a star cluster is used to determine its age?

the main sequence turnoff

Which of the rotation curves best represent the orbital speeds of stars in the Milky Way Galaxy?

the spiraly one

As a spaceship nears an event horizon, a clock on the spaceship will be observed:

to run slowly.

If a white dwarf gains sufficient mass, it can become a:

type I supernova