Chapter 16, Problem 42A

Is light emitted from the surface of a massive star red-shifted or blue-shifted by gravity?

To determine

To identify: Whether the light emitted from the surface of a massive star is red-shifted or blue-shifted by gravity.

Answer to Problem 42A

The light emitted from the surface of a massive star is red-shifted by gravity.

Explanation of Solution

Introduction:

In the development of the general relativity theory, it was predicted that as orbits of planets (elliptical) precess about the Sun, a starlight passing close to the Sun is deflected. Also, time will slow down due to gravitation.

It is observed that the light which is propagating against the gravity will have a slightly lower frequency due to the effect which is known as gravitational red-shift.

The red-light is having the low-frequency end of the visible spectrum. A reduction of frequency results in shifting of the color of the emitted light into the red light.

This effect is less in the Sun’s weak gravitational field and it is predominant in more compact stars having greater surface gravity.

Conclusion:

Thus, the light emitted is red-shifted by gravity.