Exam 15: The Milky Way Galaxy: a Spiral in Space

Most of the mass of our galaxy lies between Earth and the Galactic center.

The thickness of the Galaxy near the Sun is about 1000 light-years.

The dark halo is now believed to extend at least

Between us and the Galactic Center lie about 100 billion solar masses.

William Herschel's original model for our Galaxy was based on counting stars.

Herschel's original disk model placed us close to the center of the Galaxy.

If the Galactic Year is defined as the orbital period of the solar system, how long does it take us to circle the center? How do we know?

Contrast the open vs. globular clusters in terms of age, color, galactic distribution, chemical composition, and populations.

Herschel believed the Milky Way was a disk of stars, while Shapley found the extended halo more like a ball.

The spiral arms are made of bright stars belonging to Population .

Why aren't there young stars in the halo?

The center of the Milky Way lies in the direction of the constellation Cygnus.

Compare the way an optical and radio astronomer would map the Galaxy.

The orbits of Population II stars and globular clusters are much like comets, rising high above the galactic plane with eccentric orbits.

All RR Lyrae stars are about 5 times the Sun's luminosity.

We can estimate the mass of the Galaxy from observations of its curve.

Shapley found the globular cluster distribution equally concentrated all along the galactic plane.

According to its rotation curve, the majority of our Galaxy's mass is .

All globular cluster stars belong to Population _ .

The variables in the closer globular clusters were used by Harlow Shapley to find their distances.