Exam 19: The Expanding Universe

If a galaxy has a recessional velocity of 50,000 km/s,at what wavelength will you observe the Hαemission line? Note that the rest wavelength of the Hα emission line is 656.3 nm.

Which of the following lists distance indicators that are used to measure distances ranging from the very nearest to the very farthest?

The abundance of various elements formed from Big Bang nucleosynthesis depended only on the temperature of normal matter in the early universe.

What do astronomers mean when they say that the universe is isotropic?

If the wavelength of the background radiation peaked at 1 μm at the time of recombination,how old was the universe then compared to its age today?

Name three "rungs" in the distance ladder that let us estimate the value of the Hubble constant.

What does the value of R_U,the scale factor of the universe,tell us?

Describe the two assumptions regarding the universe that the cosmological principle makes.

To be a standard candle,an object must have a constant:

Galaxy peculiar velocities are typically about 300 km/s.How far away do you have to look in order to see galaxies recessional velocities that are 10 times this peculiar velocity?

If a galaxy has an apparent velocity of 700 km/s,what is its distance if the Hubble constant is 70 km/s/Mpc?

The current temperature of the cosmic background radiation of 2.73 K means that the peak of its spectrum occurs at a wavelength of:

If we lived in a galaxy one billion light-years from our own,what would we see?

We can measure the value of H₀ directly with no intermediate steps.

After the Big Bang,as the universe cooled and protons and electrons combined so that the universe became neutral,what important consequence happened?

If suddenly we find that the distances between the Sun and nearby stars are now 10 percent larger than we thought it was before,what measured properties will we not have to adjust?

What do astronomers mean when they say that the universe is homogeneous?

Will the Sun get larger over many billions of years?

It is possible for a galaxy to have an apparent recessional velocity greater than the speed of light.

The COBE and WMAP satellites detected fluctuations in the CMB.On average,how big were these fluctuations,and what does that tell us about the universe at a redshift of z = 1,000?