Astronomy Exam 4

Astronomers believe that the universe has a flat geometry because

Hot and cold features in the CMB have a characteristic size of about one degree on the sky.

Arrange the steps in how astronomers currently think the Milky Way formed, from earliest to latest. -Halo stars and globular clusters form Mergers further build up the Milky Way Disk of gas collapses, forming disk stars Massive cloud of gas begins developing

Massive cloud of gas begins developing -Halo stars and globular clusters form Disk of gas collapses, forming disk stars Mergers further build up the Milky Way

Why is the use of Hubble's Law to measure distances to galaxies so important to astronomers?

Most galaxies are so far away, the only way to get distances to them is to use Hubble's Law

Where in the Galaxy would you expect to find Type II (core-collapse) supernovae?

Thin disk

Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is

about 13.8 billion years

An astronomer needs to measure the distance to 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 method would astronomers use to find the distance to a remote quasar?

finding the redshift and using Hubble's Law

How does a period of extremely fast inflation very early in the history of the universe explain the observation that the geometry of the universe looks flat (not curved) to us?

inflation increased the size of the universe so much that the resulting universe looks flat from any point of view

Arrange the "rungs" of the cosmic distance ladder in a way that correctly depicts how each distance measuring technique is grounded in others for determining distances across the universe. variable stars stellar paralax Spectroscopic Paralax Type la Supernova

stellar paralax Spectroscopic Paralax variable stars Type la Supernova

When we determine the age of the universe using the Hubble Time, what important simplifying assumption goes into our calculations?

that the expansion of the universe has been happening at the same rate - neither speeding up or slowing down

How do quasars demonstrate that the universe evolves with time?

the number of quasars reached a maximum some time ago, and now the numbers have been declining

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

If quasars often resemble little blue stars, what was it about them that so surprised astronomers when they were discovered?

their spectral lines were at first hard to recognize and then turned out to have large redshifts

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 is 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

The standard bulbs (standard candles) that made it possible for astronomers to discover the acceleration in the expansion of the universe were

white dwarf (type Ia) supernovae