How can a black hole lose its mass? Is Hawking radiation the only way?

  • $\begingroup$ They can also lose lass when they merge where the final mass is less than the combined mass of the initial black holes. $\endgroup$ – A. C. A. C. Nov 22 '17 at 19:45
  • $\begingroup$ @JonCuster corrected) $\endgroup$ – user175077 Nov 22 '17 at 20:13

Hawking radiation is not the only way. Mass can also be lost in the form of gravitational waves since it takes energy to create these waves and energy is directly proportional to mass (times $c^2$).

Also note these waves are created in the event of two black holes spiraling and colliding with each other.

  • $\begingroup$ Note that gravity waves and gravitational waves are different. $\endgroup$ – Qmechanic Nov 22 '17 at 20:41
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    $\begingroup$ How does a black hole produce gravitational waves? $\endgroup$ – Rob Jeffries Nov 22 '17 at 21:10
  • $\begingroup$ maybe if it is spinning? $\endgroup$ – innisfree Nov 23 '17 at 4:15
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    $\begingroup$ @innisfree Absolutely not, which is why I made the comment. Only merging black holes emit GWs. But even there, there is no way a black hole can accrete more mass (including another black hole) and end up less massive. It is only that the final black hole has a lower mass than the sum of the contributing black holes. That is not the same as saying an individual black hole loses mass (which they never do). $\endgroup$ – Rob Jeffries Nov 23 '17 at 5:39
  • $\begingroup$ @RobJeffries What about hyperbolic orbit? I suppose there are times when you have gravitational wave emission without a merging event. In this case, is it alright to say the black hole loses mass? $\endgroup$ – Otto Nov 24 '17 at 3:55

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