Prior to the 1990s, most astronomers assumed that gamma-ray ...

[jazziefee]

Prior to the 1990s, most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks. How do we now know that this hypothesis was wrong?
 
  A) We now know that gamma-ray bursts come not from neutron stars but from black holes.
  B) Theoretical work has proven that gamma rays cannot be produced in accretion disks.
  C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky.
  D) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts occur too frequently to be attributed to neutron stars.
  E) Observations from the Compton Gamma-Ray Observatory have allowed us to trace gamma-ray bursts to pulsating variable stars in distant galaxies.

Question 2

Briefly explain why Mercury, Venus, and the Moon do not have significant erosion. Relate erosional activity to the four planetary formation properties.
 
  What will be an ideal response?

[af]

Answer to Question 1

C

Answer to Question 2

Mercury has a negligible atmosphere from the point of view of erosion, primarily due to its high temperature, related to its distance from the Sun. Its relatively small size also led to only a small amount of outgassing to form an atmosphere in the first place. The Moon also has a negligible atmosphere, primarily related to the inability of such a small world to create or retain an atmosphere. Venus has a great deal of atmosphere but very little erosion. Water erosion doesn't occur because the planet is too hot, related to its distance from the Sun. It lacks significant wind erosion because its slow rotation rate leads to very slow winds.

[jazziefee]

Excellent

[Missbam101]

TYSM