State three differences between the elliptic galaxy and the spiral galaxy.

If a galaxy has an apparent radial velocity of 2000 km/s and the Hubble constant is 70 km/s/Mpc, how far away is the galaxy?

What evidence can you cite that our galaxy has a galactic corona?

Why can't the evolution of galaxies go from elliptical to spiral? From spiral to elliptical?

Calculate the Schwarzschild radius for Milky Way.

An astronomer in an imaginary Universe observes a small patch of the sky (0.005% of the total) with very deep observations and finds one million galaxies. How many galaxies can they estimate to be present in the whole Universe? 10 billion 20 billion 50 billion O 70 billion

Figure 2 shows the "rotation curve" of NGC 2742. It plots the “radial velocity (V)" (how fast material is moving either toward or away from us) that is measured for objects at different distances (R = radius") from the center of the galaxy. The center of the galaxy is at 0 kpc (kiloparsecs) with a speed of 9 km/sec away from us. (These velocities have been corrected for the observed tilt of the galaxy and represent true orbital velocities of the stars and gas.) 200 100 U4779 -100 As you can see, one side of the galaxy is moving with a negative velocity (spinning toward us), while the other side has a positive velocity (spinning away from us). Using Newton's gravity equation, we will be able to determine the gravitational mass of the entire galaxy and how the mass varies versus distance from the galaxy's center. -200 -8 8 -4 Radius (kpc) Read the following text carefully and follow the instructions: Select five radii spaced evenly from 0-10 kpc across the galaxy. Your selections should…

The Sun is at a distance of about 8 kpc from the galactic center and moves around the galactic center in a circular path with a velocity of about 220 km s. Make a rough estimate of the mass of the Galaxy.

Astronomers estimate the mass of the stars in a certain galaxy to be about 3.0e40 kg, and the total mass of this galaxy to be about 1.2e41 kg. The amount of the galaxy’s mass is made up of dark matter is_____ percent.

The hydrogen Balmer line has a wavelength of 486.1 nm. It is shifted to 565 nm in a galaxy's spectrum. What is the radial velocity (in km/s) of the galaxy? (Indicate the direction with the sign of your answer.)