Reading Quiz 08 - Chapter 14

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Reading Quiz 08 - Chapter 14 of Understanding Our Universe

Question 1 1 pts

The cosmological principle is a testable scientific theory. Which of the following are predictions of the cosmological principle?

All of these answers are part of the cosmological principle.

An astronomy student in a galaxy 10 billion light years away would look in the opposite direction from that of the Milky Way and see the same structure.

We can observe galaxies 5 billion light years in one direction and assume the distribution is the same in another direction.

An astronomy student in a classroom 2 billion light years away would reach the same conclusions about the Universe that we do.

The distribution of galaxies 10 billion light years away is the same as the distribution of galaxies from our view.

Question 2 1 pts

Credit: ESA/Hubble & NASA. Messier 61

Constellation: Virgo

Distance: 53 million light years

(16 megaparsecs - Mpc)

Velocity (km/sec) = 1566 km/sec

Redshift (z) = 0.005224

NASA/IPAC EXTRAGALACTIC DATABASE

Let's imagine that instead of living in the Milky Way (MW) galaxy, we actually lived in the spiral galaxy Messier 61 located in the Virgo supercluster, on a planet orbiting a sun-like star. We look up the Milky Way galaxy in our online database. What do we find for its information?

All of these statements would be accurate descriptions of what we observe for the Milky Way.

The MW has a recessional velocity of 1566 km/sec.

The MW is 53 million light years away. The MW has a redshift (z) of 0.005224

Question 3 4 pts

A Venn diagram is a good way to find similarities and differences among objects. In this case, we consider galaxies; and, to make life easier, JUST elliptical and spiral galaxies, and JUST differences.

Have numbered types ranging from E0 to E7. [ Choose ]

Have disks, arms, central bulges. [ Choose ]

Entire galaxy has stars moving in all possible directions. [ Choose ]

Most stars follow nearly circular orbits, traveling in the same [ Choose ] direction.

Contain large amounts of dust and cold, dense gas [ Choose ] concentrated in the disk.

Contain no large amounts of dust and cold gas, just very hot [ Choose ] gas.

Active star formation is an on-going event. [ Choose ]

No star formation occurring. [ Choose ]

Question 4 1 pts

The textbook covers a number of events that may lead to spiral arms forming in spiral galaxies. Which one of the following answers is NOT one of those events?

Formation of massive stars and the subsequent strings of star-forming regions.

Disturbances caused by bursts of star formation.

Disturbances caused by gravitational interactions with other galaxies.

The supermassive black hole located in the centers drawing in streams of stars, gas, and dust.

An elongated bulge gravitationally disturbing the disk.

Question 5 1 pts

Since elliptical galaxies have stars orbiting in all different directions, it is not possible to measure the amount of mass present simply by using Newton's laws of gravity and motion, as is possible when measuring the amount of dark matter in spiral galaxies. What observations do astrophysicists use to confirm the presence of dark matter in elliptical galaxies?

Measurements of the massive amounts of hot, X-ray emitting gas that the elliptical galaxy has retained.

The presence of MACHOS in elliptical galaxies has been confirmed by observations at radio-wavelengths.

Since evidence shows that all elliptical galaxies contain supermassive black holes, astrophysicists measure the velocity of the orbiting stars.

Counts of the number of spiral galaxies that have merged with a given elliptical galaxy.

Question 6 1 pts

What is it about the progenitors of Type Ia supernovae that lead astronomers to the conclusion that these kinds of supernovae all have about the same luminosity?

Comparisions of observations of Type Ia supernovae in the most distant galaxies and in nearby ones, show identical luminosities.

All involve mass flowing onto a white dwarf that eventually reaches the Chandrasekhar limit and thus the same mass when it literally explodes.

Since these supernovae occurred immediately after the recombination in the Universe, we expect them to have the same luminosity.

These supernovae occur for stars that have masses between 10 and15 times that of the Sun, so it is assumed the supernovae all have identical luminosities.

Question 7 3 pts

Place each of the galaxies shown in its proper place in the Hubble's tuning fork for classifying galaxies.

GALAXY 01 GALAXY 02 GALAXY 03 GALAXY 04 GALAXY 05 GALAXY 06

A [ Choose ]

B [ Choose ]

C [ Choose ]

D [ Choose ]

E [ Choose ]

F [ Choose ]

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