Chapter 16, Problem 1STP

To determine

To Choose: The correct option.

Answer to Problem 1STP

B. $1.75\times {10}^5\text{}\text{years}$

Explanation of Solution

Given:

The believed distance of the galaxy from the Earth, $d=1.66\times {10}^{21}\text{m}$

Formula used:

  $\text{Distance}=\text{Speed}\times \text{Time}$

Calculation:

The speed of light is known as, $c=3\times {10}^8\text{}\text{m/s}$

Then, using the given values of time and speed of light, the time taken by the light to travel to Earth is,

  $\begin{array}{c}\text{Time}=\frac{\text{Distance}}{\text{Speed}}\\ =\frac{1.66\times {10}^{21}}{3.0\times {10}^8}\\ =0.5534\times {10}^{13}\text{s}\times \frac{1\text{}\text{h}}{3600\text{s}}\times \frac{1\text{}\text{day}}{24\text{h}}\times \frac{1\text{}\text{year}}{365\text{days}}\\ =1.75\times {10}^5\text{}\text{years}\end{array}$

Conclusion:

Hence, the supernova explosion actually occurred $1.75\times {10}^5\text{}\text{years}$ prior.