There is some big space news coming in the next year.
It will be on the front pages of the newspapers and all over the internet,
because if everything goes according to plan, we will be getting the first-ever picture
of a black hole.
Physicists calculated centuries ago that an object with enough gravity could trap even light.
But black holes have been hard to observe
up close because they’re either too small, too far away, or both.
“To see the supermassive black hole at the center of our galaxy -- it would be like taking
a photograph of a DVD on the surface of the moon.”
The mass of the Milky Way’s central black hole is over 4 million times greater than
our sun. But it’s diameter just 17 times larger.
And most black holes are smaller than that.
That’s why every image you’ve seen of a black hole up close, well, those are illustrations
made by artists. But if astronomers haven’t observed black
holes directly, why are they fairly certain they exist?
Well they’ve observed the effects of black holes on other things, like these stars at
the center of our galaxy. “This is a time-lapse of over 16 years of
observations of stars near the center of our Milky Way galaxy and it’s been sped up by
a factor of some 32 million times. So this is a lot of time over just a couple of seconds.
And what it’s showing is that these stars are seemingly
orbiting something in the center of our galaxy.” The only known object that could cause those
orbits, and that’s so small, is a supermassive black hole.
Another way to spot black holes is by the glowing material spiraling toward to their
event horizon, or the point of no return. Friction heats this matter up tens of millions
of degrees, and anything that hot emits x-rays we can observe.
Here’s a pair of galaxies that passed through each other. There are at least 9 small but
active black holes here, but you can only see them when you look at the x-ray layer.
These dots are x-ray sources from supermassive black holes at the center of
galaxies 3 to 10 billion light-years away. And that’s just from this small patch of
sky. Some supermassive black holes also shoot off
gigantic jets of particles at nearly the speed of light, seen here in radio wave data from
the galaxy m87, which has a much bigger black hole than the one in the center of the Milky
Way. "Sometimes black holes at the center of galaxies
can shoot off jets of material that are larger than the galaxies themselves.
The jets don’t come out of black hole. Rather they seem to result from nearby matter interacting
explosively with the spin of the black hole. No other known source of energy could power
these things. Over time, the jets create huge lobes of particles
that glow in radio waves but aren’t visible in optical light.
You can see them surrounding this galaxy cluster 2.6 billion light-years away.
The x-ray layer shows how the jets from the black hole in the central galaxy displaced
some of the hot gas nearby. Just to give you a sense of how big this is,
our entire galaxy could fit several times over inside
these gas cavities. The historic first picture of a black hole
won’t show one of these super active monsters, though.
They’re targeting our own black hole at the center of the Milky Way, which flares up
occasionally but is relatively quiet. And they’re doing it by creating what’s
called the Event Horizon Telescope, which is this worldwide effort to kind of link up
a lot of different radio telescopes around the world.
They’re looking at radio waves rather than optical light to see through the thick clouds
of gas and dust near the galactic center. the researchers will correlate the waveforms
from the distant telescopes to boost the signal and quiet the noise.
There’s so much data involved that it has to be flown on airplanes. But once it gets
translated into an image, They expect to see a dark round silhouette
surrounded by bright matter swirling around the event horizon, and it will be brighter on the side
where the matter is moving toward us. And if they see something else entirely, well
that could be even more interesting.
"What I can say here is that I don't know what we're gonna see. By the way,
that is a disclaimer about all of this. I have no idea what we're gonna see with this,
which is part of the reason we get up in the morning. Because if we knew
what we were going to see, it would be engineering. But the reason it’s science is because we don’t
know, but what we can put ourselves in a good position to do is to have high signal to noise ratio data. And
that is what I’m increasingly convinced that we're gonna have.”