We know that black hole mergers are a thing, as LIGO has detected gravity waves from these exact events.
To get too much more specific, we need to ponder the mass of the black holes and their distance of separation.
You did specify that these black holes were of equal size. They would orbit each other, potentially for billions of years, just like any two other massive objects and how these orbits behaved would depend on their mass, orbital distance, relative velocity and the gravitational influence of any other large bodies. For example, two 30 solar mass black holes orbiting close to Sagittarius A* (our galaxy’s central super massive black hole) would have a very different orbital pattern from the same two black holes orbiting each other in intergalactic space.
gravity waves
Nitpick: Gravity wave ≠ gravitational wave :)
Black holes merge. It doesn’t matter what size they are. It’s not that the bigger one eats the smaller one they just merge.
Are we advanced enough to have seen this yet? Not calling you a liar just sounds interesting to watch…
Yes, LIGO has observed the gravitational wave “chirp” from two black holes orbiting each other closer and closer until they join
I am on my phone at the moment is it LGO or L I G O?
It stands for Laser Interferometer Gravitational Wave Observatory!
The black holes are so big and fast when they spiral in and merge that they literally create waves in spacetime which change the length of things by a tiny amount as they pass by us and LIGO is able to measure when the two arms of it change length by nanometers and that’s where we got the signal.
There’s also The Event Horizon Telescope which made radio images of the black hole at the center of our galaxy. We haven’t been able to catch a merger with this though.
pretty sure that we can’t “watch” a black hole at all, since we need light to see and light cannot escape a black hole
We can see them from the luminance of their accretion disks, or via gravitational lensing, or polar radiation jets, or gravitational waves
Ok dumb question if we can’t see or watch a black hole how do we know what they do or even exist?
you should really read the Wikipedia article on black holes: https://en.wikipedia.org/wiki/Black_hole
some paragraphs you might find relevant to your question:
By nature, black holes do not themselves emit any electromagnetic radiation other than the hypothetical Hawking radiation, so astrophysicists searching for black holes must generally rely on indirect observations. For example, a black hole’s existence can sometimes be inferred by observing its gravitational influence on its surroundings.
David Finkelstein, in 1958, first published the interpretation of “black hole” as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known was Cygnus X-1, identified by several researchers independently in 1971.
The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Any matter that falls toward a black hole can form an external accretion disk heated by friction, forming quasars, some of the brightest objects in the universe. Stars passing too close to a supermassive black hole can be shredded into streamers that shine very brightly before being “swallowed.”[11] If other stars are orbiting a black hole, their orbits can be used to determine the black hole’s mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems and established that the radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses.
I’ll echo the other replies that the gravitational waves from black hole mergers have been detected by LIGO. In fact, the 2017 Nobel Prize in physics was awarded to members of this collaboration specifically for this feat.
We haven’t (yet) seen a pair of black holes collide using light directly, but the gravitational waves have been perfectly consistent with general relativity calculations. Here’s a video from LIGO that shows what one of these simulations looks like, for a simulation that reproduces a detected gravitational wave.
As an aside, right around the time the LIGO team was awarded the Nobel prize, they detected the collision of a pair of neutron stars. They alerted the astronomy community to the direction they saw the signal from, and within a day there were telescope observations of light from the kilonova that resulted from the collision. Ultimately various sensors recorded optical light, infrared, ultraviolet, gamma rays, and radio waves being emitted from the explosion. The hope is that someday we’ll get lucky enough to see similar photon signatures from a black hole merger!
The LIGO video is beautiful and terrifying all at the same time.
Yes! And this happening is exactly what allowed gravity waves to first be detected
gravity waves
Nitpick: Gravity wave ≠ gravitational wave :)
Interesting!
Yeah
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