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  • When I was a kid, a few things kept me up at night.

  • Namely the Bermuda Triangle, quicksand, and black holes.

  • Turns out, as an adult these things are way less of a day-to-day problem than I thought

  • they'd be.

  • Now I'm lying awake at night all over again, because astronomers have just found the closest

  • black hole to us yet, and they suggest there could be even more lurking out there in the universe.

  • Finding black holes is tricky, what with them capturing everything that strays too close,

  • including light.

  • They are 'unseeable' by their very nature, and only the effects of their intense gravity

  • give them away.

  • They are the sarlaccs of space, the insatiable invisible maw of destruction.

  • So, it's a bit ironic that the researchers who found this nearby black hole weren't

  • even looking for it.

  • The astronomers were looking at what they thought was a double star system called HR

  • 6819.

  • Not the most fear-inducing name I've ever heard of, but just wait.

  • This pair of stars is close enough that it can be seen from the Southern Hemisphere without

  • any optical aids on a dark and clear night.

  • While observing the stars, the astronomers noticed that what they were actually seeing

  • was a three body system.

  • The inner star appeared to orbit something once every 40 days, while the outer star orbited

  • the pair much farther away, I assume out of a sense of self-preservation.

  • So, how did the researchers know the object the inner star was orbiting was a black hole?

  • Well, whatever it was orbiting was invisible, which is a pretty strong clue.

  • But they could also use the inner star's orbit to determine the mass of its invisible

  • partner, which they determined had a mass about four times that of our Sun.

  • Based on those two pieces of information, the third member of this stellar tango is

  • most likely a black hole.

  • This makes HR 6819 the first star system with a black hole that can be seen with the naked eye.

  • Perhaps the most intriguing thing, or worrying thing depending on how paranoid you are, is

  • just how mundane this black hole is.

  • Up until now, we've only spotted a few dozen black holes in our galaxy, and usually they

  • stick out because of how violently they interact with their surroundings.

  • They're siphoning off matter from companion stars and blasting x-rays out into space.

  • By contrast, the black hole hidden in HR 6819 doesn't seem to be doing much of anything,

  • so it appears truly black.

  • It's just quietly waltzing with its partners, minding its own business.

  • But it's very existence hints at much more.

  • If we found one this close by and this easily, then in all likelihood there are many more

  • black holes just like it throughout our galaxy.

  • We've long suspected that throughout the history of the Milky Way many stars must have

  • collapsed into themselves, and discovering this quiet black hole could explain why we

  • haven't seen more yet.

  • The astronomers who led this study estimate that there must be hundreds of millions of

  • them out there.

  • So, should you be terrified that there are scores of black holes around every corner

  • waiting to get you like an army of darkness?

  • In all seriousness, no.

  • HR 6819 is about 1,000 light years away.

  • For perspective, the nearest star to our solar system is a little over four light years away.

  • If anything, discovering this quiet black hole opens up opportunities to understand

  • how large stars evolve or how three body systems can trigger black hole mergers and stellar

  • collisions.

  • And besides, if a black hole were to get youyou'd never see it coming.

  • Well, sleep tight everyone!

  • Do you devour any information about black holes that comes within your reach?

  • Then check out our playlist on black holes here!

  • Make sure to subscribe for more videos like this, and as always, thanks for watching.

  • I'll see you next time.

When I was a kid, a few things kept me up at night.

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This Black Hole Is So Close You Can “See” It, Here’s How

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    Summer posted on 2020/08/10
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