<p>It's called a black hole merger, or coalescence. <a href="http://www.youtube.com/watch?v=GVds0q0y5RM">Here</a> a simulation video.</p>

<p>Even the formation of the event horizons of the two initial black holes takes "super long" in Earth's time. That's similar with the merger. On the other hand we are very close to the completed merger within a short "Earth's" time seen from a distance, as soon as the merger starts. General relativity as well as quantum theory are incomplete with what will happen very close to a presumed singularity or at the presumed event horizon; this will remain disputed until a satisfying theory of <a href="http://en.wikipedia.org/wiki/Quantum_gravity">quantum gravity</a> is found.</p>

<p>Mergers of black holes are likely to occur, e.g. when two galaxies collide, the momentum of the central supermassive black holes (SMBH) is slowed down by consumption of gas, dust and stars, until the SMBHs merge to the central SMBH of the merged galaxy.
<a href="http://www.youtube.com/watch?v=_FlGiqPdbx8">Here</a> a galaxy merger simulation.</p>

<p><a href="http://www.youtube.com/watch?v=eTlF_0rJF8Y">Here</a> a simulation of the coalescence of two black holes within a collapsing star.</p>

<p><a href="http://en.wikipedia.org/wiki/Binary_black_hole">More on black hole binaries on Wikipedia</a>.</p>

CC BY-SA 3.0
2017-11-07T12:19:37.233Z
Is it coalescence of their horizon event expected to radiate GW? Or real coalescence / merging of mass (eventually singularities into one, whatever they are treated) take place later? In particular if we assume two identical BH. Shall I made a new Q out of this?
Alchimista
CC BY-SA 3.0
2014-04-05T13:59:26.193Z
Thank you, nice. I like this https://www.youtube.com/watch?v=p647WrQd684 and https://www.youtube.com/watch?v=Dxfx3NIanHk
user1346
CC BY-SA 3.0
2014-04-05T12:48:40.997Z
2014-04-05T13:02:53.243Z
2014-04-05T13:02:53.243Z
Gerald
<p>There is a large number of visible <a href="https://en.wikipedia.org/wiki/Supernova" rel="nofollow noreferrer">Supernovae</a>. Each week - about twenty Supernovas Type 1a around the Universe.</p>
<p>Are there collisions of Black Holes? What is this collision called?</p>
<p>E.g. two black holes come close to each other. There are event horizons for both black holes, will there be such collision super long in Earth's time?</p>

CC BY-SA 4.0
2024-08-07T09:24:30.383Z
[Type Ia supernovae](https://en.wikipedia.org/wiki/Type_Ia_supernova) don't create black holes. They totally blow up. *"Type Ia supernova leaves no compact remnant, but the whole mass of the former white dwarf dissipates through space."*
PM 2Ring
CC BY-SA 4.0
2024-08-07T17:22:51.090Z
@PM2Ring *I'm guessing* that (ten years ago) the OP was just using superovae as an example of some astronomical phenomenon that happens fairly frequently, and compared to that, how infrequent is a different astronomical phenomenon. I don't think they meant to imply that the two were related.
uhoh
CC BY-SA 4.0
2024-08-07T17:52:22.267Z
@uhoh Maybe, but I think it's more likely that the OP believed they *are* related. However, I don't write comments directed to people who haven't been seen for over a decade. ;) My comment was intended for *anyone* who may be misled into thinking that type Ia supernovae create black holes.
PM 2Ring
CC BY-SA 3.0
2014-04-07T17:59:08.833Z
This is actually a very hot topic of research as BH mergers should produce strong gravitational waves which the next generation of detectors hope to identify.
chris
<black-hole><collision>
Collision of two black holes
user1346
# Collision of two black holes

(Asked by: username_0 on 2014-04-05)

There is a large number of visible [Supernovae](https://en.wikipedia.org/wiki/Supernova). Each week - about twenty Supernovas Type 1a around the Universe.

Are there collisions of Black Holes? What is this collision called?

E.g. two black holes come close to each other. There are event horizons for both black holes, will there be such collision super long in Earth's time?

**Tags:** black-hole, collision

> **Comments:**
> **username_3**: This is actually a very hot topic of research as BH mergers should produce strong gravitational waves which the next generation of detectors hope to identify.  
> **username_1**: [Type Ia supernovae](https://en.wikipedia.org/wiki/Type_Ia_supernova) don't create black holes. They totally blow up. *"Type Ia supernova leaves no compact remnant, but the whole mass of the former white dwarf dissipates through space."*  
> **username_2**: @PM2Ring *I'm guessing* that (ten years ago) the OP was just using superovae as an example of some astronomical phenomenon that happens fairly frequently, and compared to that, how infrequent is a different astronomical phenomenon. I don't think they meant to imply that the two were related.  
> **username_1**: @username_2 Maybe, but I think it's more likely that the OP believed they *are* related. However, I don't write comments directed to people who haven't been seen for over a decade. ;) My comment was intended for *anyone* who may be misled into thinking that type Ia supernovae create black holes.  

---

## 1 answers

### Answer by username_4 on 2014-04-05. Score: 6 | Accepted answer

It's called a black hole merger, or coalescence. [Here](http://www.youtube.com/watch?v=GVds0q0y5RM) a simulation video.

Even the formation of the event horizons of the two initial black holes takes "super long" in Earth's time. That's similar with the merger. On the other hand we are very close to the completed merger within a short "Earth's" time seen from a distance, as soon as the merger starts. General relativity as well as quantum theory are incomplete with what will happen very close to a presumed singularity or at the presumed event horizon; this will remain disputed until a satisfying theory of [quantum gravity](http://en.wikipedia.org/wiki/Quantum_gravity) is found.

Mergers of black holes are likely to occur, e.g. when two galaxies collide, the momentum of the central supermassive black holes (SMBH) is slowed down by consumption of gas, dust and stars, until the SMBHs merge to the central SMBH of the merged galaxy.
[Here](http://www.youtube.com/watch?v=_FlGiqPdbx8) a galaxy merger simulation.

[Here](http://www.youtube.com/watch?v=eTlF_0rJF8Y) a simulation of the coalescence of two black holes within a collapsing star.

[More on black hole binaries on Wikipedia](http://en.wikipedia.org/wiki/Binary_black_hole).

> **Comments:**
> **username_0**: Thank you, nice. I like this https://www.youtube.com/watch?v=p647WrQd684 and https://www.youtube.com/watch?v=Dxfx3NIanHk  
> **username_5**: Is it coalescence of their horizon event expected to radiate GW? Or real coalescence / merging of mass (eventually singularities into one, whatever they are treated) take place later? In particular if we assume two identical BH. Shall I made a new Q out of this?  

---

