Why every picture of a black hole is an illustration1

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 pictureof a black hole. Physicists calculated centuries ago that an object with enough gravity could trap even light. But black holes have been hard to observeup 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 takinga 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 thanour 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 illustrationsmade by artists.  But if astronomers haven’t observed blackholes directly, why are they fairly certain they exist?Well they’ve observed the effects of black holes on other things, like these stars atthe center of our galaxy.  “This is a time-lapse of over 16 years ofobservations of stars near the center of our Milky Way galaxy and it’s been sped up bya 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 seeminglyorbiting something in the center of our galaxy. ” The only known object that could cause thoseorbits, and that’s so small, is a supermassive black hole. Another way to spot black holes is by the glowing material spiraling toward to theirevent horizon, or the point of no return.  Friction heats this matter up tens of millionsof 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 butactive 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 ofgalaxies 3 to 10 billion light-years away.  And that’s just from this small patch ofsky.  Some supermassive black holes also shoot offgigantic jets of particles at nearly the speed of light, seen here in radio wave data fromthe galaxy m87, which has a much bigger black hole than the one in the center of the MilkyWay.  "Sometimes black holes at the center of galaxiescan 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 interactingexplosively with the spin of the black hole.  No other known source of energy could powerthese things.  Over time, the jets create huge lobes of particlesthat 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 displacedsome of the hot gas nearby.  Just to give you a sense of how big this is,our entire galaxy could fit several times over insidethese gas cavities.  The historic first picture of a black holewon’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 upoccasionally but is relatively quiet.  And they’re doing it by creating what’scalled the Event Horizon Telescope, which is this worldwide effort to kind of link upa lot of different radio telescopes around the world. They’re looking at radio waves rather than optical light to see through the thick cloudsof gas and dust near the galactic center.  the researchers will correlate the waveformsfrom 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 getstranslated into an image, They expect to see a dark round silhouettesurrounded by bright matter swirling around the event horizon, and it will be brighter on the sidewhere the matter is moving toward us.  And if they see something else entirely, wellthat 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 knewwhat we were going to see, it would be engineering.  But the reason it’s science is because we don’tknow, but what we can put ourselves in a good position to do is to have high signal to noise ratio data.  Andthat is what I’m increasingly convinced that we're gonna have. ”