Chapter 16

How old is our universe?

14 billion years

What is the most accurate way to determine the distance to a nearby star?

Stellar parallax

Cosmological redshift is the result of:

The expansion of the universe

We determine the distance of a Cepheid variable by:

Determine its luminosity from the period-luminosity relation and then applying the inverse square law for light

What is Hubble's law?

The recession velocity of a galaxy is directly proportional to its distance

The luminosity of a quasar is generated in a region the size of

the solar system

A standard candle is:

A light source of known luminosity

Why do virtually all the galaxies in the universe appear to be moving away from our own?

Because expansion causes all galaxies to move away from nearly all others

Why are Cepheid variables important in astronomy?

Cepheids variables are pulsating stars whose pulsation periods are directly related to their true luminosities. Therefor they can be used as distance indicators.

Which of the following is NOT one of the three major categories of galaxies?

Globular galaxies

According to the theory that active galactic nuclei are powered by supermassive black holes, the high luminosity of an active galactic nucleus primarily consists of:

Light emitted by hot gas in an accretion disk that swirls around the black hole

What is the best way to determine a galaxy's redshift?

Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory.

What is a quasar?

The extremely bright center of a distant galaxy, thought to be powered by a supermassive black hole

We can study how galaxies evolve because:

The farther away we look, the further back in time we see

What does Hubble's law tell us?

The more distant a galaxy, the faster it is moving away from us

Which of the following methods is the best method for measuring distances to extremely distant galaxies?

White dwarf supernova method