Astronomy Unit 4

59 terms by amendmd

Create a new folder

Like this study set? Create a free account to save it.

Create a free Quizlet account to save it and study later.

Sign up for an account

Already have a Quizlet account? .

Create an account

Advertisement Upgrade to remove ads

The odds of the Universe being as Flat as is observed is _____

highly unlikely and needs further explanation

Whether or not the Universe is Open, Flat or Closed depends on

the average density of the Universe

The Milky Way Galaxy_____

does not have an Active Galactic Nucleus

Why are type I supernova such excellent standard candles?

They all have a known absolute luminosity

If galaxy A is four times more distant than Galaxy B, then according to the Hubble Law, galaxy A will recede ______ than galaxy B

4 times faster

Most of the matter in the Universe is apparently


s0 galaxies are sometimes referred to as

Lenticular Galaxies

The rate of variation in brightness of an object_______ of the size of the in terms of light time.

Sets the upper limit

Some large clusters of galaxies do not appear to contain enough mass to hold themselves togethers


Seyfet galaxies are spiral galaxies with active cores


When we speak of the "expanding universe", what is actually growing larger?

Space between galaxy clusters is growing larger

Inflation solves_____

the flatness problem and the horizon problem

The flatness problem and the horizon problem______

Are solved if there was a sudden inflation of the Universe at time before recombination occured

Elliptical galaxies contain more gas, dust and young stars than do Sa galaxies.


Look-back time is______

The difference in the age of the universe now and the age of the universe when the photons were emitted by some distant object

Measurements of Type-1a Supernova made in the last few years indicate that

the expansion rate of our universe appears to be increasing

The Cosmological Principle assumes that____

the universe is homogeneous and isotropic throughout space. the laws of physics and the values of physical constants are the same. all observers see the same universe.

Arno Penzia and Robert Wilson found that the Cosmic Microwave Background Radiation to be

incredibly smooth in all directions

Whether the Universe is open, closed or flat depends on the ______ of Universe


The Hubble constant can only be used to measure the distances to

galaxies that are more distant than the members of the Local Group

Why are Type 1a Supernovae all the same luminosity?

All white dwarfs collapsing into Neutron stars do so at the Chandrasekhar Limit, thus limiting their energy output

The assumption of homogeneity states____

the universe looks the same from all locations over sufficiently great distances

If the average density of the Universe is less than the critical density, the Universe is open


The Milky Way and the Andromeda Galaxy will merge in about______ years

5 billion

Quasars must be small because they______

fluctuate rapidly in luminosity

The unified model describes active galactic nuclei (AGN) using________

a super massive black hole surrounded by an accretion disk and dense torus of gas

The closest group of galaxies to the Local Group is _______

The Sculptor Group

The Big Bang is responsible for the creation of _________

Hydrogen, Helium, and very very small trace amounts of Deuterium, Tritium, and Lithium

In order to use Cepheid variables to measure distances to other galaxies, we must be able to______

resolve those individual stars in that galaxy

Early attempts to explain the spectrum of the first quasar were unsuccessful because the lines were

red shifted much more than normal for an object that bright

The closest Cluster of galaxies to the Local Group is________

The Virgo Cluster

What is a characteristic of a Seyfert galaxy?

Emmission lines of Hydrogen. A very bright nucleus with respect to the rest of the galaxy. Normal narrow spectral lines of typical stars.

That the radio lobes radiate synchrotron radiation indicates that____--_

high speed electrons are spiraling through a magnetic field.

The Milky Way galaxy is part of

the Local Group

The Virgo Cluster______

is a rich cluster and the closest cluster of galaxies outside of the Local Group

The assumption of universality states______

that the physical laws we observe on Earth apply everywhere in the universe

If the expansion rate of the Universe is accelerating, the Universe should move towards_______

The Big Rip

Gravitationally bound collections of galaxies containing less than 200 members are called

a group

Powerful Radio Galaxies, first discovered in the 1950s, often show evidence of

violent activity at their centers, jets of matter streaming from their centers, and radio emitting lobes on either side of the galaxy

The flatness problem is that____

the density of the Universe is very close to the critical density

The size of quasars is thought to be_____

about the size of our solar system

Measured ages of globular clusters suggests that the Universe is

at least 12 billion years old

The observed motions of the galaxies within the Local Group are _____ than would be explained by the luminous matter observed

Much faster

Matter and Anti-Matter came into existence

in very nearly equal, but not identical quantities

The lobes of Radio Galaxies______

are much larger than the optical part of the galaxy

Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in the universe is expected to be

The very small dwarf galaxies

A puzzling aspect of quasars is______

their great brightness, their great distance,their small size

The assumption of isotropy states______

that the universe looks the same in all directions over sufficiently great distances

Quasars are found_______

to be more numerous in the early Universe

Measurements of Type 1a Supernova made in the last few years indicates that

the expansion rate of our universe appears to be increasing

The Universe was opaque before the 300,000 year age because______

emitted photons were immediately absorbed by free electrons

The value of the Hubble Parameter is _______ km/sec/MPc


The great distances of quasars, implied by their large red shifts, together with their apparent magnitude as seen from Earth, tells us that Quasars are______

highly luminous

The energy involved with Quasars, Blazars, Seyfert Galaxies (type 1 & 2) can be explained by the presence of

super-massive black holes in the nuclei of some galaxies actively consuming matter

When the Universe cooled to about 3000 Kelvin

Electrons adhered to atoms and the Universe became transparent to radiation

When viewed through a telescope a quasar appears as a


Most of the mass of a galaxy is______

contained in the dark matter of the galaxy

How do astronomers find the distances to quasars?

by applying Hubble's Law to their redshift values

If viewed from another distant cluster of galaxies, our group of galaxies containing the Milky Way and the Andromeda would appear to have______

only a few members

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set