Cepheid variable stars stop pulsating when: A) they evolve out ...

[NguyenJ]

Cepheid variable stars stop pulsating when:
 
  A) they evolve out of the instability strip of the H-R diagram.
  B) they enter the zero-age main sequence.
  C) they begin their stable lives fusing hydrogen.
  D) they reach the lower edge of the main sequence of the H-R diagram.

Question 2

__________are objects used to map spiral arms.
 
  A) Spiral locators
  B) Spiral tracers
  C) Arm finders
  D) Spiral waves

[Toya9913]

Answer to Question 1

A

Answer to Question 2

B

[NguyenJ]

TYSM

[Animal_Goddess]

Thanks for the timely response, appreciate it