Chapter 4.5, Problem 58E

To determine

To find out the number of stars in the universe.

Answer to Problem 58E

  ${10}^{22}$

Explanation of Solution

Given information: There are 100 billion stars in a galaxy and there are 100 billion galaxies in the universe.

Formula used:The product of powers rule is used. $a^x\times a^y=a^{x+y}$

Calculation:

Number of stars in a galaxy is 100 billion

  $=100\times {10}^9$ As mentioned, 1 billion $={10}^{11}$

  $={10}^2\times {10}^9$

  $={10}^{2+9}$

  $={10}^{11}$

Now, there are 100 billion galaxies in the universe.

Hence, number of stars in a galaxy are

  $={10}^{11}\times {10}^{11}$

  $={10}^{11}\times {10}^{11}$

  $={10}^{22}$ stars in the galaxy