Exam 16: Galaxies

Because the Hubble constant has a value of 70 km/s/Mpc, a galaxy with a recession velocity of 21,000 km/s must be _______________ Mpc from Earth. (Express your answer as a whole number of Mpc)

In which of the following types of galaxies would you expect to find active star formation?

Which types of galaxies would contain very little gas and dust?

The mass of visible matter in a galaxy can be estimated by measuring its luminosity. When this is compared with the measured mass of the galaxy, astronomers find that ____.

How are standard candles used to measure distance?

All elliptical galaxies are more massive than the largest spiral galaxies.

One of the rare galaxies that is isolated in space is likely to be a(n) ____.

Galaxies contain 10 times as much dark matter as visible matter.

A key piece of evidence that leads astronomers to conclude that most galaxies include a supermassive black hole in the center is that ____.

Dark matter is detectable in the coronae of ____.

The Hubble law is one of the most important relations in modern astronomy because it ____.

Because t he Hubble constant has a value of 70 km/s/Mpc, a galaxy 100 Mpc away would have a recession velocity of ____.

A standard candle is an object with a known luminosity.

The mass of a galaxy's central black hole is proportional to the mass of its _______________.

Hot, low-density gas can be detected in galactic clusters through X-ray emission. The gas is important in understanding dark matter because ____.

Gentle tidal interactions are probably necessary to support the formation of _______________ in a galaxy.

The ____ depend(s) on the assumption that the mass of a galaxy or galactic cluster is large enough to keep moving matter bound to the main structure.

Is dark matter important in other galaxies and galactic clusters?

Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them as distant clouds of billions of stars.

Cepheid variables are useful in measuring the distance to ____.