Name: 科学者たちが衝突コース上にある2つの超巨大ブラックホールを発見 (Scientists Just Detected Two Supermassive Black Holes on a Collision Course)
Uploaded: 2021-01-14T10:47:12.000Z
Duration: 4 min 10 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

基礎受動態

Supermassive black holes are thought to be at the center of most galaxies, and they are

The Milky Way's own supermassive black hole, Sagittarius A*, is about 4 million times the

But scientists have just spotted two absolute behemoths, that dwarf Sagittarius A*,

It's the first time such massive black holes have been spotted this close together, and

it could help us detect a hum of gravitational background noise.

Of course “close” is a relative term and in this particular instance when scientists

say close, they mean about 1,400 light-years apart.

The black holes are located about 2.5 billion light-years from us, so since the light from

them took 2.5 billion years to reach us, we're observing them as they were 2.5 billion years ago.

Coincidentally, the scientists who discovered them estimate that that's about how long

They could be going all smashy smashy right now, unleashing huge gravitational waves millions

of times more powerful than those previously detected by LIGO and Virgo.

Of course, because of how far away they are, the waves won't reach us for 2.5 billion

We've observed stellar mass black holes merging, but we're not sure if their supermassive

counterparts can join forces megazord-style too.

It seems odd, I mean, these things each have an incredible gravitational pull, why wouldn't

Right now the thinking is when galaxies merge, their supermassive black holes begin to orbit

As they do, dust and stars in between them sap some of their energy, causing their orbits

But as they get closer, that region of space between them shrinks, until theoretically

The two black holes find themselves stably orbiting each other but never getting closer,

like you and your crush at an 8th grade dance.

Some studies suggest that happens at about 1 parsec, or roughly 3.2 light-years distance,

so it's known as the final parsec problem.

But all that is theoretical, and we're lacking more observational data.

It's possible our predictions are wrong and black holes of this size do merge instead

Unfortunately, black hole pairs are very hard to spot.

Remember how I said this is the closest we've seen two this big and they're 1,400 light-years

1 parsec is way too close for us to distinguish two supermassive black holes apart.

And now that we've found these two, it's not like we can wait around 2.5 billion years

But since we've spotted these two, we can start to guess how common merging supermassive

Based on their findings the scientists estimate that optimistically there are 112 black holes

whose gravitational waves we can detect from Earth.

This would make a kind of constant hum, the scientists likened this gravitational background

Normally it'd be impossible to distinguish one cricket from another.

But if there's no final parsec problem and they can merge, it should create a massive

When that happens, the waves will be at frequencies outside what LIGO and Virgo can detect.

So instead, scientists will have to keep a close eye on pulsars, special stars that send

If a supermassive merger stretches or compresses the space between us and a pulsar, the rhythm

These frequency changes are so small, just tens to hundreds of Nanohertz,

it will require close to a decade of observation to spot the weak signal hiding in the noise.

They're searching for more pairs of black holes to refine their prediction further,

but it's possible we never detect a merger and the final parsec problem is insurmountable

Thanks for watching, don't forget to subscribe for more videos, like Amanda's here on what

And while LIGO can't detect supermassive mergers, it was recently upgraded, making

it 40% more sensitive as it continues its hunt for merging stellar mass black holes.

Well that's all for now, I'll see you next time on Seeker.