What kind of universe represents the critical point were the universe never collapses on itself
what kind of properties do irregular galaxies have?
typically smaller than spiral galaxies, exhibit vigorous star-forming activity, some show evidence for prior collision or close encounter with another galaxy.
What is true about galaxies that are measured from earth with high speeds?
They are moving away from Earth and are farther from Earth than galaxies with lower speeds.
what can we say about the galaxies measured from earth at low speeds?
They are moving away from earth and are closer to earth than galaxies with high speeds.
Suppose that galaxy B is twicw as far from Earth as galaxy A. Hubbles law predicts that galaxy B will be moving away from earth with approximatley _____.
twice the velocity of galaxy A.
Using the method of standard candles, we can, in principal, find the distance to a campfire if we know.
The number of logs used
If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be
The astronomer who orginally classified galaxies into Spiral, Elliptical, and Irregular
A galaxy with little cool gas or dust and no evidence of ongoing star formation is most likely a
Within the boundaries of the constellations Coma and Virgo are found in
the largest nearby superclusters of galaxies
In active galaxies, their central engines may be temporarily fed by
a close encounter with a neighbor galaxy
True or False: Collisions between galaxies are rare and have little or no effect on the stars and interstellar gas in the galaxies involved
True or False: On the largest scales, galaxies in the universe appear to be arranged on huge sheets surrounding nearly empty voids.
As we look at larger and larger scales the universe we find
a larger and larger percentage of the matter is dark
Based on galactic rotation curves and cluster dynamics, we think of dark matter
comprieses of over 90% of the entire mass of the universe
A radio galaxy whose lobes are swept back as if forming a tail, what dose this probably indicate
This is evidence for intergalactic matter.
collisions between galaxies
cause the gas and dust clouds to collide, leading to rapid star formation
Where are large dust clouds predominately located in the galaxy M51?
Within or on the edges of the spiral arms
Where are the ionization nebulae predominately located in the galaxy M51?
Within or on the edges of the spiral arms of the galaxy
True or False: Stars and Gas in the Galactic disk move in roughly circular orbits around the Galactic Center.
True or False: The most likely explanation of the high-speed motion of stars and gas near the Galactic center is that stars and gas are orbiting a supermassive black hole
A cepheid variable star with a luminosity 1000 times that of the sun has a pulsation period of roughly
The first attempt to map the Galaxy via star counts was done by
William Herschel in the late 18th century
Why was Herschel's for mapping the galaxy flawed?
He relied on on visual wavelengths, which are obscuredd by dust
Detailed measurements of the disk and central bulge region of our galaxy suggest our Milky Way is a
Barred spiral galaxy
What two observations allow us to calculate the galaxy's mass?
The suns orbital velocity and its distance from the Galactic Center
True or False: Herschel believed the Milky Way was a disk of stars, while Shapely found the extended halo more like a ball
True or False: The Globular star clusters are the most obvious examples of population II around us
True or False:The density wave theory attempts to explain why the spiral arm structure persist over a long time
During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter
What important event occurred earliest in the history of the universe
Space time rapidly expanded during a brief period of inflation
During the history of the universe, what important event occurred about 380,000 years after the Big Bang
Light began to travel freely through the universe.
Essentially all the hydrogen nuclei that will ever exist in our universe was created
by the time the universe was about 3 minutes old
Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is
fainter and has most of its photons at longer wavelengths
The concept that on the grandest of scales, the universe is similar in appearance everywhere is
From the 1970s to the present, the accepted value of H has almost doubled, so
the age of the universe is half what we believed
What is the meaning of a "closed" universe?
The universe will someday stop expanding and begin collapsing inward
The latest studies from ________ led to the discovery of "dark energy."
Type I supernovae at very large red shifts
The discovery of the cosmic microwave background was important because
it was was experimental verification of a prediction from the Big Bang theory
Why didn't elements heavier than helium form in the first minutes of creation?
When He-4 was formed, the expansion cooled the cosmos below 100 million K
True or False: In the cosmological principle, we can easily test cosmic homogeneity with the red shift surveys, but isotropy cannot be so tested.
True or False: It appears that nearly three times as much dark energy exists in the universe than normal and dark matter combined
True or False:Deuterium abundance suggests that normal matter makes up only 3-4% of the critical density.