Exam 20: The Milky Waya Normal Spiral Galaxy

By comparing globular clusters,you find that Cluster A's RR Lyrae stars are 225 times fainter than Cluster B's RR Lyrae stars.You know that both clusters have approximately the same chemical composition and age,and thus their RR Lyrae stars should have the same luminosities.Which cluster has the larger distance,and what is the ratio of the clusters' distances?

Which stars in our Milky Way galaxy have orbits that are NOT similar to stars in elliptical galaxies?

There is a black hole at the center of the Milky Way that is rapidly accreting stars and gas.

A typical globular cluster is composed of 500,000 stars in a sphere whose radius is approximately 15 light-years.The distance between stars in a globular cluster is given approximately by ,where r is the radius and N is the number of stars in the cluster.Calculate this distance,and determine how many times smaller it is than the typical distance between stars in the solar neighborhood,which is 3 light-years.

Open clusters are only found in the disk of the Milky Way;globular clusters are only found in the halo of the Milky Way.

Why is the supermassive black hole in the center of our galaxy not an AGN right now? Could it be active in the future? Why or why not?

The Sun is rotating about the center of the galaxy at roughly 220 km/s at a distance of about 27,000 light-years.How long will it take to complete one revolution?

Calculate the size of the event horizon of the supermassive black hole at the center of the Milky Way,the mass of which is .Give your answer in units of AU.

Do we know whether or not the dark matter in the Milky Way is made up of planets,white dwarfs,neutron stars,and black holes?

Based on the chemical abundances and velocities of stars in the Milky Way's disk and halo,we can conclude that the protogalactic fragments that came together to form the galaxy merged when the fragments had

How do we know that globular cluster stars were not the first stars that formed in our galaxy?

Cosmic rays are

The Milky Way is classified as an __________ galaxy.

If the Large Magellanic Cloud is orbiting the Milky Way in a circular orbit with a speed of 175 km/s and a distance of 165,000 light-years from the center,how long would it take for the Large Magellanic Cloud to complete one orbit around the Milky Way?

The oldest open cluster known in the Milky Way is about 6 billion years younger than the average globular cluster.

By comparing globular clusters,you find that Cluster A's RR Lyrae stars are 100 times fainter than Cluster B's RR Lyrae stars.You know that both clusters have approximately the same chemical composition and age,and thus their RR Lyrae stars should have the same luminosities.Which is TRUE about the clusters' distances?

If RR Lyrae stars in a globular cluster had an apparent magnitude of 12 and an absolute magnitude of 0.5,what would the globular cluster's distance be?

Our galaxy is a typical barred spiral galaxy.

Cosmic rays in the Milky Way are important because

There are many more individual stars residing in the Milky Way stellar halo than inside globular clusters.