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  • [♩INTRO]

  • In 2016, two Caltech astronomers proposed

  • that our solar system is home to nine planets.

  • And no, they didn't reclassify Pluto.

  • Instead, they found evidence for a hypothetical Neptune-sized planet

  • at least forty billion kilometers from the Sun

  • far enough that it would take fifteen thousand years for it to complete one orbit.

  • In the last three years, this Planet 9 hypothesis has continued to gain support.

  • But last week, two other scientists proposed

  • that this object could be something a little more exotic.

  • Instead of a planet out there, they say it could be a black hole,

  • but like...a tiny black hole.

  • Like, the size of your fist.

  • Like...a chihuahua's head!

  • This paper hasn't gone through peer-review yet, but it's making some big claims.

  • And one way or another, it could teach us more

  • about what's lurking in our solar system.

  • This whole Planet 9 thing came about after researchers noticed something strange

  • about the outskirts of the solar system.

  • There's a lot of small rocky and icy bodies out there,

  • and many of them have weird orbits.

  • Ones so weird that they seem to be affected by the gravitational pull of some larger,

  • unknown body - something between 5-15 times the mass of Earth.

  • If there's something out there, it's probably a planet,

  • but technically, any object with the right amount of mass would do.

  • Including a special kind of black hole.

  • Normally, black holes form from massive stars,

  • so they're millions of times heavier than the Earth.

  • But there's a hypothetical kind of black hole that could be much lighter

  • like, five to fifteen times the mass of our planet.

  • They're called primordial black holes,

  • and they may have been created shortly after the universe began.

  • At that time, everything in existence was packed close together.

  • And as the idea goes, primordial black holes formed

  • when extra dense pockets of matter collapsed in on themselves.

  • According to this new hypothesis, an object like this could have been captured

  • by the Sun's gravity, and it would easily explain

  • all the weird orbits we've seen past Neptune.

  • Now, since black holes are so dense, this thing would be small

  • only about nine centimeters across.

  • But it might still be easier to spot than a distant planet.

  • At least, if you don't rely on visible light.

  • Scientists believe that primordial black holes would be surrounded by halos of dark matter.

  • This is a type of matter we can't directly detect,

  • but that most evidence suggests is out there.

  • The authors of this paper argue that, occasionally, dark matter around the black hole

  • could interact with similar particles and turn into gamma radiation.

  • Lucky for us, we have telescopes that can pick that up.

  • So theoretically, if we started seeing gamma ray flashes out past Neptune,

  • it could be a sign that we have a local black hole.

  • This hypothesis is definitely in need of more evidence, but even if it doesn't pan out,

  • searching for a primordial black hole wouldn't be useless.

  • It would likely allow us to learn more about dark matter, primordial black holes,

  • and the flashes of gamma rays we've already detected.

  • So one way or another, it seems like a possibility worth investigating.

  • In other black hole news, because it's that kind of week,

  • a handful of telescopes has detected something super hardcore:

  • A black hole three hundred seventy-five million light-years away,

  • ripping apart a star with the power of gravity.

  • The results were published last week in The Astrophysical Journal.

  • The discovery itself happened in January,

  • and the first instrument to notice something going on was NASA's TESS.

  • TESS has been orbiting Earth for a little over a year now,

  • and it stares at one large section of sky for several weeks at a time.

  • Its main goal is to find planets beyond the solar system, but because it's just floating

  • around out there with its proverbial eyes open,

  • it's bound to observe other phenomena, too. And that's what happened last winter.

  • In January, the telescope picked up an increase in brightness coming from a distant star.

  • Then, several days later, less-sensitive instruments on the ground noticed the same thing.

  • The event came to be called ASASSN-19bt

  • after the first project to give us data about it.

  • Because even though TESS technically saw it first,

  • it only sends data to Earth every two weeks, so the other team got the naming rights.

  • This brightening turned out to be the early stages of a tidal disruption event, or TDE.

  • Which is a scientific way of saying a star is getting absolutely wrecked by a black hole.

  • The murderous culprit sits at the center of a galaxy calledokay, don't make me say that.

  • I don't know how to say that.

  • Look, you're never going to visit this thing.

  • The bigger point is that this black hole seems to be

  • about six million times more massive than the Sun.

  • That's fifty percent more massive than

  • the supermassive black hole at the center of the Milky Way.

  • The more mass an object has,

  • the more of a gravitational pull it has on the stuff around it.

  • So when a star wandered too close to this black hole, things got messy.

  • The difference in gravity between one side of the star and the other became so great

  • that it overcame the forces holding the star together.

  • In other words, the black hole ripped the star apart.

  • Some of the star's gas and plasma likely escaped into the void of space,

  • but the rest tumbled down toward the black hole,

  • creating a swirling disk and a large flare of radiation we could see from Earth.

  • Tidal disruption events are super rare, and scientists have only captured

  • about forty of them so far.

  • That means each new observation can teach us something.

  • In this case, observing the event early-on allowed researchers

  • to chart the extreme drop in the star's temperature that happened

  • within the first few days.

  • It went from forty thousand degrees Celsius to only twenty thousand.

  • Something like this was in our prediction models, but now we have actual evidence.

  • Scientists will continue to study this event, both with TESS and with other instruments.

  • And ultimately, their data will help them develop better models for how TDEs happen.

  • From tiny, hypothetical objects to monsters that rip apart stars,

  • there's a lot in the news about black holes this week.

  • But if these papers show us anything, it's that there's always more to learn.

  • Thanks for watching this episode of SciShow Space News!

  • Before you go, I have an update for you!

  • Every month, we release a new, space-themed pin,

  • and October's pin is officially available!

  • It's of Sputnik, humanity's first artificial satellite,

  • and it's very, very good and shiny and fun.

  • And you can only get it during the month of October, so if you're interested,

  • check out the link in the description or the merch shelf below the video.

  • [♩OUTRO]

[♩INTRO]

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