According to the turn-off points of the oldest globular clusters, ...

[aabwk4]

According to the turn-off points of the oldest globular clusters, they are about
 
  A) 4.5 billion years old.
  B) 6.8 billion years old.
  C) 10 billion years old.
  D) 12 billion years old.
  E) 16 billion years old.

Question 2

According to the theory that active galactic nuclei are powered by supermassive black holes, the energy released as light comes from ________.
 
  A) matter-antimatter annihilation occurring just outside the event horizon of the black hole
  B) gravitational potential energy released by matter that is falling toward the black hole
  C) jets emerging from the accretion disk
  D) nuclear fusion in the accretion disk surrounding the black hole

[skipfourms123]

Answer to Question 1

D

Answer to Question 2

B

[aabwk4]

Gracias!

[mochi09]

Excellent