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?

If you want to look for old stars with low amounts of heavy elements, the best place to look out of the following locations is

How would we explain why are there are no known disk stars with exceptionally low abundances of massive elements?

The "normal" mass of the Milky Way (stars and interstellar medium together) is estimated at 100 billion-200 billion solar masses.The total mass of the galaxy measured by its rotation curve, however, is estimated in the interval of 1 trillion-1.5 trillion solar masses.How do we explain this discrepancy? What fraction of the Milky Way's mass is "normal"?

Explain why within the galactic disk we can find older stars that have higher abundances of massive elements than younger stars at larger radii from the center.

Andromeda and the Milky Way are approaching at a measured relative speed of 110 km/s.If Andromeda is currently separated from the Milky Way by about 770 kpc, provide a simple estimate for how far in the cosmic future the two galaxies will collide.Why is this estimate "simple," and not correct?

In which part of the Milky Way would you find little or no neutral hydrogen, no current star formation, and stars that are all older than 10 billion years?

The Large Magellanic Cloud is about 50 kpc from the center of the Milky Way and moves around it at about 170 km/s, as shown in the figure below.What is the inferred mass of the galaxy enclosed within this radial extent?

Why is it that, when astronomers look in the direction of the Sun's motion around the galaxy, that we see many stars that are blueshifted?

The motion and chemical composition of stars in the outer halo may suggest that

What is expected to happen to our Solar System when the Andromeda and Milky Way galaxies collide?

The gamma-ray bubbles at the poles of our galaxy are evidence that the nucleus of the Milky Way was once a(n)

Magnetic fields in the Milky Way are concentrated in the disk because

Most of the mass in our galaxy is in the form of

Any single star in the Milky Way Galaxy has the same elemental abundances as

In the figure below, we expect the absorption lines in the indicated star's spectrum to be

What observed property of the Milky Way suggests that it must contain a large amount of matter not in the form of stars, gas, or dust?

In a star that has heavy-element abundance similar to the Sun's, what percentage of the star's mass is made up of elements heavier than hydrogen and helium?

What type of standard candles did Shapley use to determine distances to globular clusters?

Halo stars near the Sun are distinguished from disk stars by what characteristics?