The Mystery of the Naked Black Hole (sciencemag.org)

sciencehabit writes: Most, if not all, galaxies have supermassive black holes at their centers surrounded by dense clouds of stars. Now, researchers have found one that seems to have lost almost its entire entourage. The team, which reported its find at the annual meeting of the American Astronomical Society, says it doesn't know what stripped the stars away. But it has put forward a tantalizing possibility: The object could be an extremely rare medium-sized black hole, which theorists have predicted but observers have never seen.

Comments

Re:Not an astronomer, obviously

[AthanasiusKircher]

How do we know the black hole itself didn't strip the stars away? That's kinda what they do, isn't it?

Not really, or at least not anymore than stripping the planets in the solar system away is "kinda what" the sun does. Contrary to the popular image, black holes aren't like giant vacuum cleaners that suck stuff in. Most of them tend to have lots of things in stable orbits around them, as stars have planets, and planets have moons. The only stuff that tends to fall in is stuff that gets directed towards them. A giant black hole at the center of a galaxy would only tend to consume stars which were "thrown" toward it, usually by unstable orbital dynamics created by encounters with other stars.

confusing title

[ooloorie]

A "naked singularity" is usually what people call a black hole without an event horizon, an object that's pretty important in theoretical physics. Calling something a "naked black hole" is kind of confusing. https://en.wikipedia.org/wiki/...

Re:confusing title

[Rei]

You totally missed the person's point. It's not about using the word "black hole" when they should have used the term "singularity" (note: black hole and singularity are not synonyms). It's that a "naked singularity" is a very specific term, and it doesn't mean "a black hole not surrounded by stars" - it means a black hole without an event horizon. This is an important concept in physics because there's a number of situations that seem like they should be able to produce one (such as strongly rotating black holes), but if you had one, relativity would break down near it. The event horizon in a black hole "protects" our universe from the effects of any weirdness inside the hole (such as a singularity, if they actually do exist), but with a naked singularity you have no such "protection". The concept exposes an area of weakness in our current understanding of physics.

Calling a black hole without stars a "naked black hole" would be like calling a jacket made out of a very transparent plastic an "invisibility cloak". It's using words that can be seen to make sense (you can't see it, so it's an invisibility cloak!), but it gives readers the totally wrong impression of what is being discussed.