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A Naked Black Hole Is Screaming Through the Universe (gizmodo.com)
New submitter PongoX11 writes: Millions of years ago, B3 1715+425 was just an ordinary supermassive black hole. It had a comfortable life, of devouring stars and belching deadly x-rays, at the center of its distant galaxy. Now, starless and alone, it's screaming through space at 2,000 kilometers per second -- and it may never stop. BC 1715+425's troubles began when its galaxy bumped up against another. This isn't all that unusual: in fact, astronomers believe that the largest galaxies in our universe formed during ancient mergers. Normally, when two galaxies collide, the supermassive black holes at their centers start to orbit one another, moving closer and closer together in an inescapable gravitational attraction. Eventually, those black holes can fuse, releasing a burst of energy as gravitational waves and completing the cosmic joining. Most of the time, this process seems to work out for all parties involved, judging from the fact that nearly all supermassive black holes reside at the center of galaxies, and nearly all galactic centers contain a supermassive black hole. But every now and then, something goes wrong and cosmic wreckage ensues. B3 1715+425, speeding away from the core of a bloated galactic merger 2 billion light years from Earth, is living proof of this. The working theory is that millions of years ago, B3 1715+425's galaxy passed through a much larger galaxy (one that had formed during many previous mergers) and got shredded to bits, a bit like a paper airplane flying into a hurricane. The leftovers include a faint galactic remnant, just 3,000 light years across, and the supermassive black hole itself, nearly naked and hemorrhaging ionized gas as it tears through the void. "We were looking for orbiting pairs of supermassive black holes, with one offset from the center of a galaxy, as telltale evidence of a previous galaxy merger," said James Condon, the astronomer at the National Radio Astronomy Observatory who led the study. "Instead, we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it."
Why is it the heavier they are the more they like running around naked?
How do you know that? Their relative velocity would depend on how fast the galaxies were moving together, and the escape velocities would depend on how close they passed by one another.
Sheesh, evil *and* a jerk. -- Jade
Indeed if two black holes started very far away from each other and never passed so close to each other that newtonian approximation breaks down _and_ in empty space this would be true. However they are not in empty space but pass thru both galaxies flinging stars to very energetic orbits as they go. This is called dynamical friction and is usually enough to bind the two black holes.
Screaming through the universe?
In space no one can hear you scream.
"By definition, objects a long distance from each other are outside each other's escape velocity"
Excellent. So we don't need to worry about the Death Asteroid.
The collision must have happened more than 2 billion years ago, or we wouldn't know about it yet.
Speaking of galactic collisions, theres a new eBook out from Ian Douglas called Altered Starscape
(Ian Douglas is the author of the Star Carrier series and also writes under his real name of William H Keith)
This new series is called "Andromeda Dark" so its probably not much of a spoiler to tell you that the other galaxy involved is M31
Highly recommended for fans of Space Fleet / Galactic Empire science fiction
I would have thought "A Naked Black Hole Is STREAKING Through the Universe" would have been the obvious headline.
On the other hand I grew up in the 60's-70's...
we found this black hole fleeing from the larger galaxy and leaving a trail of debris behind it.
Sounds like a standard relationship breakup to me...
Um, a naked black hole is actually a very specific thing (a singularity without an event horizon) that may or may not even exist in nature. Just skimming the article, this sounds like an ordinary black hole to me.
Just a regular, hairless yet non-naked black hole. That's what it sounds like.
When I first saw the headline, I thought they were talking about a Naked Singularity. Now that would have been interesting.
Me too. I was intensely excited for several seconds.
B) Eliminate all the stupid users. This is frowned upon by society.
Galaxies typically form in gravitationally-bound clusters. and the super-massive black holes form at the centre of the galaxies; i.e. they co-move with the galaxies. If two galaxies from the same cluster merge, the holes at their cores do not have relative escape-velocity and end up gravitationally bound.
The interesting point in the current story is that the black hole has picked up much more velocity and escaped. I.e. it is exceptional.
For a planet like earth, the orbital velocity is much greater than the escape velocity, even at the surface.
But galaxies are different. The speed of the milky way relative to the CMB is about the same as its escape velocity from here.
So it is very easy for two galaxies to collide at less than their escape velocity. The time-scale is tens of millions of years, at least.
It's just a really, really terribly written article.
There is a theoretical object called a "naked singularity", a black hole without an event horizon, which stuff actually would be able to escape from. This isn't one of those. The author's calling it "naked" because it doesn't have any of the usual stuff around it...except it's not even that. It's the remnants of the core of a galaxy: a few thousand stars, some gas, and a black hole. The x-rays come from surrounding debris falling into it, not the black hole itself. The black hole isn't hemorrhaging anything, the gas is just debris that the core wasn't able to hold onto after the collision that stripped most of the rest of its stars and gas away. It doesn't even mean anything to say "it may never stop"...stop relative to what?
It's just sensationalized gibberish.