Through the use of various measurement techniques, it has been found that most galaxies are rapidly receding (moving away) from the Milky Way, and in fact, galaxies in distant superclusters are moving away from us more rapidly than nearby superclusters.  This recessional motion is present throughout the Universe and is called the

Assume that a typical galaxy contains about 200 billion stars and that there are more than 150 billion galaxies in the known universe. Estimate the total number of stars in the universe.

Calculate the Hubble constant for a universe which is 10 billion years old.

Suppose you have obtained spectra of several galaxies and have measuerd the observed wavelength of the H-Alpha line (rest wavelength = 656.3 nm) to be Galaxy 1: 658.1 nm. Galaxy 2: 667.1 nm. Galaxy 3: 677.6 nm. Assuming a Hubble Constant of 72.5 km/s/Mpc, calculate the distance to each of these galaxies (answer in Mpc)

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…

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.

What is the estimated age of the Universe (in years) if the Hubble constant is 60 km/s/Mpc?