Possible equations (choose the correct one): =1012/H; H=v/d. If ...

[WhattoUnderstand]

Possible equations (choose the correct one):  =1012/H; H=v/d. If gravity is unimportant and H equals 75 km/s/Mpc, then the age of the universe is about
 
  a. 8.9 billion years.
  b. 13 billion years.
  c. 16.6 billion years.
  d. 26 billion years.
  e. 74 billion years.

Question 2

Why do many planetary nebulae show ring-like features on the sky instead of spheres?
 
  What will be an ideal response?

[javimendoza7]

Answer to Question 1

b

Answer to Question 2

Asymmetry is the rule in planetary nebulae rather than the exception. A number of causes have been suggested. A disk of gas around a star's equator might form during the slow-wind stage and then deflect the fast wind into oppositely directed flows. Another star or planets orbiting the dying star, rapid rotation, or magnetic fields might cause peculiar shapes.

[WhattoUnderstand]

TY

[javimendoza7]

You're welcome