91Ó°ÊÓ

If a galaxy has an apparent radial velocity of \(2000 \mathrm{km} / \mathrm{s}\) and the Hubble constant is \(70 \mathrm{km} / \mathrm{s} / \mathrm{Mpc}\), how far away is the galaxy? (Hint: Use the Hubble law.)

Suppose you found a galaxy in which the outer stars have orbital velocities of \(150 \mathrm{km} / \mathrm{s}\). If the radius of the galaxy is \(4 \mathrm{kpc}\), what is the orbital period of the outer stars? (Note: \(1 \mathrm{pc}=3.08 \times 10^{13} \mathrm{km}\) and \(1 \mathrm{yr}=3.16 \times 10^{7}\) seconds.

Among the globular clusters orbiting a distant galaxy, one is moving at \(420 \mathrm{km} / \mathrm{s}\) and is located \(11 \mathrm{kpc}\) from the center of the galaxy Assuming the globular cluster is located outside most of the mass of the galaxy, what is the mass of the galaxy? (Hints: Use the formula for circular velocity, Chapter 4. Remember to convert units to meters and kilograms.)

If the jet in \(\mathrm{NGC} 5128\) is traveling at \(5000 \mathrm{km} / \mathrm{s}\) and is \(40 \mathrm{kpc}\) long. how long will it take for gas to travel from the core of the galaxy to the end of the jet? (Hint: 1 pc equals 3 \(\times 10^{13} \mathrm{km} .\) )

Explain the features of this radio image of the galaxy IC 708 The hydrogen Balmer line \(\mathrm{H}_{\beta}\) has a wavelength of \(486.1 \mathrm{nm}\). It is shifted to \(563.9 \mathrm{nm}\) in the spectrum of \(3 \mathrm{C}\) 273. What is the redshift of this quasar? (Hint: What is \(\Delta \lambda\) ?)

If a quasar is 1000 times more luminous than an entire galaxy, what is the absolute magnitude of such a quasar? Note, the absolute magnitude of a bright galaxy is about -21.