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  • [ intro ]

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

  • we can't see them directly,

  • astronomers estimate our galaxy is peppered

  • with anywhere from ten million to a billion black holes.

  • They're all remnants of stars

  • 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 againour models are sometimes wrong.

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

  • but much bigger.

  • According to models,

  • the biggest black hole made from a single star like that

  • couldn't exceed twenty-five solar masses.

  • Except

  • 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.

  • It's called LB-1,

  • and the paper's authors calculated

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

  • Based on patterns in the star's light,

  • they found that the star was moving

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

  • days.

  • That indicated it was orbiting something.

  • Something the team couldn't detect.

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

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

  • And the results were pretty telling.

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

  • just based on how the star was moving

  • was about six solar masses.

  • Technically, that means it could be star.

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

  • So, instead, the team proposed

  • this companion had to be a black hole.

  • After analyzing more data,

  • they estimated that the actual mass of this thing

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

  • And that's where things get messy.

  • 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

  • and helium.

  • And according to models,

  • 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.

  • Not fifty-five to seventy-nine.

  • 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,

  • and it's not actively consuming matter.

  • So this discovery could mean

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

  • just waiting to be found.

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

  • Journal with evidence that planets

  • 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!]

  • It does give me context though,

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

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

  • the circumnuclear disk.

  • 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,

  • you don't just need distance.

  • 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,

  • each about ten times the mass of Earth and orbiting at various distances.

  • Admittedly, the planet-making process didn't happen quite like normal.

  • Among other things, the planets took about four hundred million years to form,

  • which is several times longer than what happened in our solar system.

  • But hey, they formed around a supermassive black hole.

  • It makes sense that things would happen differently.

  • These results are amazing to think about, but they only came from a model.

  • We're still a very long way from finding planets like thisif they're really

  • out there.

  • After all, it was only this year that we managed to image the shadow of a supermassive black

  • hole.

  • Finding a planet amongst all of that will be way more difficult.

  • The authors actually point out the usual methods of finding planets are,

  • and I quote, “hopeless.”

  • But there couldmaybepossibly

  • be something in X-ray or radio wave data.

  • Still, when you think about it,

  • it used to be impossible to detect any planets around other stars

  • so who knows what we'll be capable of in the future?

  • Thanks for watching this episode of SciShow Space News!

  • Before you go, we've got two quick announcements for you.

  • First, this episode is brought to you by our President of Space, SR Foxley!

  • SR is one of our patrons on Patreon

  • and is part of the community that keeps SciShow going.

  • So, thanks for your support!

  • And also!

  • It's December,

  • which means it's calendar-shopping time!

  • If you're in the market for a 2020 calendar, consider checking out our lunar calendar.

  • It's super satisfying to look at and displays the phase of the moon for every day of the

  • year.

  • So you can always know what's going on up there.

  • You can find them in our merch shelf below, or at DFTBA.com.

  • [ outro ]

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