Name: ブラックホールの周りに惑星ができるかも!| サイショウニュース (Planets Could Form Around Black Holes! | SciShow News)
Uploaded: 2021-01-14T08:35:54.000Z
Duration: 7 min 21 s
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程度の副詞

Just in case you need something to keep you up at night.

様態の副詞

astronomers estimate our galaxy is peppered

with anywhere from ten million to a billion black holes.

whose cores collapsed into infinitesimally small points.

And while each is bizarre and braain-bendy in its own way,

models tell us that these objects at least have limits.

But, then again… our models are sometimes wrong.

Like, picture a star with a composition similar to the Sun's,

the biggest black hole made from a single star like that

couldn't exceed twenty-five solar masses.

astronomers just found one weighing in at more than twice that.

They published their mystery last week in the journal Nature.

And it might require rethinking exactly how massive stars evolve.

This black hole was found while astronomers were looking

at data from a star about eight times more massive than the Sun.

that it's roughly fourteen thousand light-years away.

getting closer to, then farther from Earth over a period of about seventy-nine Earth

That indicated it was orbiting something.

Still, even though they couldn't see the mystery object,

they could use data from LB-1 to estimate its mass.

Based on the calculations, the smallest possible mass for this object

— just based on how the star was moving —

Technically, that means it could be star.

But a star that massive would be bright enough for us to detect it.

they estimated that the actual mass of this thing

is between fifty-five and seventy-nine times the mass of our Sun.

Because those numbers are more than twice the mass

we thought possible given the black hole's surroundings.

See, both LB-1 and the surrounding area contain a decent amount of elements other than hydrogen

single stars can't form huge black holes in that kind of environment.

They should lose too much material at the end of their lives.

So if they do become black holes, they should peak around twenty-five solar masses.

So this discovery might mean we need to go back

and modify our models for how stars evolve.

But it may also mean that something else is going on.

For instance, the authors of this paper have suggested that, well,

maybe LB-1's black hole didn't come from a single star after all.

Maybe, this system used to have three stars —

but after one collapsed into a black hole, it ate one of the remaining two.

Alternatively, maybe there are two, less-massive black holes here,

and they're orbiting each other so closely that we can't tell them apart.

Of course, it could also turn out that the distance measurements of LB-1 are incorrect,

since some of the team's data do disagree with other sources.

And that would seriously mess up the math.

But regardless of how that plays out, this black hole will still be special.

Right now, it's the only stellar-mass black hole

we've found that can't be observed in the X-ray part of the electromagnetic spectrum.

That means it's not stealing gas off its companion star,

there's an entire population of these secret black hole companions,

In other black holes news, a group of astronomers published a paper last week in The Astrophysical

— planets! — could apparently form around supermassive black holes.

And I don't mean, like, the black hole's gravity captured them.

I mean planets could form around black holes like they do around stars.

Just when you think you understand the universe,

black holes show up and ruin everything!]

I'm glad that our planet is orbiting 'not a black hole'

According to the paper, the action happens in what's called

This is a thin disk of dust and gas a ways away from the black hole —

much farther than the accretion disk that feeds the thing.

Out there, the black hole's gravity isn't overpowering,

so particles could collect into a giant ball of rock.

But if you're going to make a planet around a black hole,

Your circumnuclear disk also needs to be dense.

Partly because, well, you need a lot of stuff to make a planet.

But also, because you need something to block radiation from the accretion disk.

Otherwise, the outer region of the circumnuclear disk will be too hot,

and grains of ice and dust won't be able to stay solid and bind together.

In theory, black holes should be able to check these boxes, no problem.

But in the new paper, one team decided to actually test this.

They applied current models for planetary formation to the circumnuclear disk of a supermassive

black hole that was actively eating matter.

And their model generated eighty-five thousand planets,

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ブラックホールの周りに惑星ができるかも!| サイショウニュース (Planets Could Form Around Black Holes! | SciShow News)

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