Astronomy | Astrophysics Answers

Describe a simple thought experiment to prove that blackbody radiation is isotropic; that is,
the observed spectral brightness of a blackbody disc is independent of its orientation.

The Milky Way is moving toward the larger galaxy M31 at about 100 kilometers per second. M31 is about 2 million light years away. How long will it take before the Milky Way collides with M31 if it continues at this speed?

. If we detected radio signals of intelligent origin from the Andromeda Galaxy (M31) and immediately responded with a radio message of our own, how long would we have to wait for a reply?

If the Milky Way were the size of a nickel (about 2 centimeters).

a. How big would the Local Group be?
b. How big would the Local Supercluster be?
c. How big would the visible Universe be?

During the 1960s and 1970s, The Apollo spacecraft took humans to the Moon in three days. Traveling to Mars requires a trip of around 2 AU in total. How long would this trip take, traveling at the same speed as to the Moon?

If the Earth were a volley ball what would be the diameter of the Sun? What object matches
this size?

What would be the circumference and diameter of a ball that would represent the Moon if the Earth were a volleyball? What kind of object matches this size?

A galaxy of absolute magnitude of −20 is at a distance of 100 kpc. Would it be visibleto
the naked eye?

Using the virial theorem, explain why there is a need to postulate the existence of dark
matter.

What is a Seyfert galaxy? Explain how broad-line and narrow-line regions originate in a
Seyfert galaxy