Super massive black holes are usually millions of times more massive than stellar mass black holes. I have read on SE and over internet that 3M☉ worth of energy is released in black hole mergers (not sure which type of merger). I have tow related questions:

  1. What is the difference in energy released from a stellar mass black hole merger vs. a supermassive black hole merger?

  2. How much energy will be released in the super massive black hole merger when Milky way and Andromeda will merge in few billion years?


2 Answers 2


Too long for a comment, but it's an incomplete answer.

The gravity waves detected were from a stellar mass binary black hole merger, sometimes abbreviated bbh for binary black hole.

The two black holes are thought to be about 36 and 29 solar masses with a final combined mass of about 62. So, roughly 5% of the black hole mass turned into into gravitational wave energy. Source.

and from Wikipedia article (which can be taken with a grain of salt)

As the orbiting black holes give off these waves, the orbit decays, and the orbital period decreases. This stage is called binary black hole inspiral. The black holes will merge once they are close enough. Once merged, the single hole settles down to a stable form, via a stage called ringdown, where any distortion in the shape is dissipated as more gravitational waves.3 In the final fraction of a second the black holes can reach extremely high velocity, and the gravitational wave amplitude reaches its peak.

The existence of stellar-mass binary black holes (and gravitational waves themselves) were finally confirmed when LIGO detected GW150914 (detected September 2015, announced February 2016), a distinctive gravitational wave signature of two merging stellar-mass black holes of around 30 solar masses each, occurring about 1.3 billion light years away. In its final moments of spiraling inward and merging, GW150914 released around 3 solar masses as gravitational energy, peaking at a rate of 3.6×1049 watts — more than the combined power of all light radiated by all the stars in the observable universe put together.3[4][5] Supermassive binary black hole candidates have been found but as yet, not categorically proven

Supermassive bbh are thought to have been observed, see here and we may see one in our lifetime, not sure how often they happen. But beyond that, I have no way of knowing how much more energetic a supermassive BBH merger would be other than to say, I would think, a whole lot, as it would have to scale upwards by some formula.

With the case of Andromeda and the Milky Way, we're talking Andromeda's 100 million solar mass black hole and the Milky way's 4-6 million solar masses. Maybe someone here can estimate, but if the energy output is even 5%-10% of the smaller of the two, that's still a few hundred thousand solar masses of energy, an absolutely crazy energy output. Even if it's far smaller than a few hundred thousand solar masses, it's still enormous energy.

I'm also not sure if it's a dangerous form of energy output as it basically squashes things back and forth maybe a couple times before returning them to normal. I have no idea what the safe distance is from that kind of merger and gravity wave creation. Interesting question though. Fun to think about.

  • 2
    $\begingroup$ " I have no idea what the safe distance is from that kind of merger and gravity wave creation." I was going to ask this as my next question once I had an answer to this question :) . $\endgroup$
    – Knu8
    Commented May 28, 2016 at 13:27
  • $\begingroup$ It's a good question, maybe someone here knows. $\endgroup$
    – userLTK
    Commented May 28, 2016 at 13:28
  • $\begingroup$ Most of the energy released is in the form of gravitational waves. I have no idea at that scale, how "dangerous" it can be. $\endgroup$
    – Knu8
    Commented May 28, 2016 at 13:31

Super massive and stellar mass black holes are different in mass and size.. Since we cannot describe nor we can be certain in either of their mass or size .. It's completely impossible (for the time being) to answer whether or not how much difference there will be regarding their energy release and the amount it releases..Yes,the energy is high 3 solar mass .. but the energy cannot be determined regarding there are various factors which leads to the determination of Mass and energy.

  • $\begingroup$ Are you really sure we can not know the mass of black holes? $\endgroup$ Commented May 28, 2016 at 11:06
  • $\begingroup$ @Shrey We can determine the mass of black holes by their gravitational influence. Your assertion is completely wrong. $\endgroup$
    – Knu8
    Commented May 28, 2016 at 11:19

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