What is the difference between and intrinsic variable star and an extrinsic variable star?

This is a picture of what object or feature? [Image 1]    [Image 2] [Image 3]    [Image 4]

An iron core cannot support a star because:

Explain how the Doppler effect works. Relate this to the determination of the radial velocity of a celestial object.

The primary constituent of large complexes called Giant Molecular Clouds is

What event triggers the transition from a red giant stage to the next stage in a star’s evolution?

Short Answer Questions Answer the following five short-answer questions in complete sentences. 

A Type II Supernova can produce a black hole.

Star A is spectral class A5 and star B is spectral class B5. They have the same apparent brightness. They are both main sequence stars. Which star is farther away?

Given the formula m – M = 5logd – 5 what is the distance to a star with an m of 5 and an M of -5? (d is in parsecs)