59 terms

Astronomy Unit 4

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