The great contribution of Nicholas Copernicus was to ________. ...

[natalie2426]

The great contribution of Nicholas Copernicus was to ________.
 
  A) create a detailed model of our solar system with the Sun rather than Earth at the center
  B) discover the laws of planetary motion
  C) discover the law of gravity
  D) prove that the Earth is not the center of the universe

Question 2

The average speed of stars relative to the Sun in the solar neighborhood is about 20 km/s. Suppose you discover a star in the solar neighborhood that is moving relative to the Sun at a much higher speed, say 220 km/s.
 
  What kind of orbit does this star probably have around the Milky Way? In what part of the galaxy does it spend most of its time? Explain.

[stanleka1]

Answer to Question 1

A

Answer to Question 2

Since stars that are traveling along with us in the disk of the Milky Way move at a velocity relative to us of only about 20 km/sec, we would reason that a star observed to be moving relative to us at a velocity of 220 km/sec was not traveling with us in the disk but was part of some other component of the Milky Way, likely the halo. The orbits of halo stars are not concentrated in the flattened disk but are distributed more like a sphere. So a halo star flying through the disk would appear to us to have the rotational speed of the disk, namely 220 km/sec.

[natalie2426]

TY

[stanleka1]

You're welcome