Posted by “Einstein was wrong when he said, ‘God does not play dice.’ Consideration of black holes suggests, not only that God does play dice, but that he sometimes confuses us by throwing them where they can’t be seen.” -Stephen Hawking
Welcome back to Starts With A Bang after a brief vacation! Apparently, I go away for a few days, and the world tries to turn all we know about supermassive black holes on its head!
Think about any galaxy like ours. Tens of thousands of light years across with great spiral arms, they house anywhere upwards of a hundred billion stars. If you take a good look at any large galaxy — like NGC 1097 shown here — you’ll notice something very exciting about its center.
But you won’t necessarily notice it in visible light; take a look at what happens if we look at NGC 1097 in the infrared.
It’s much more noticeable that there’s something exciting going on at the center. What is it? Why, it’s a supermassive black hole! We’ve got one at the center of our galaxy, of course, that we can actually measure by following the paths of individual stars orbiting around it!
But what about other galaxies? How do we know how massive their central black holes are?
Let’s take a look at a spectacular example in the relatively nearby Universe.
This is M87, a giant elliptical galaxy about a million light years in diameter. At the heart of the Virgo cluster, it’s the largest galaxy around us for over a hundred million light years.
And so, you’d expect, there should be a giant black hole at the center. It might, you’d suppose, be much bigger than the one at the center of the Milky Way. But how could you tell? Let’s remember what black holes do to the matter around them.
Matter should orbit the black hole, just like the planets orbit our Sun, in the same plane that the black hole rotates. But instead of making a perfectly stable accretion disk, gravity and dynamical friction will pull that matter in towards the center. And some of it will fall right on in, helping to grow the black hole.
But some of it gets shot out, perpendicular to the disk, in a great jet. Additionally, if a large object falls in, or if too much mass accretes in the disk, you can get a large, flaring outburst.
Well, if there’s any galaxy that should show these features, it would be the largest one, with the (in theory) largest black hole, right?
Hell yeah it is! Take a look at the jet coming from M87; it’s over 5,000 light years long and is moving nearly at the speed of light! It’s so powerful that it appears to have knocked the central black hole nearly 100 light years away from the true galactic center in the opposite direction!
But what about those flaring outbursts I mentioned? Are those there? We need to use Chandra, and look in the X-ray to find out.
That’s right; we see evidence of flares bursting out from the central black hole every 6 million years or so, with the hot gas tracing out those trails. We can also observe the speed that the disk revolves, and that helps us estimate the mass of the black hole, too.
Based on these types of observations, we previously estimated the mass of this black hole to be 6.4 billion times our Sun, but there’s a new observation in town.
New measurements of the gas show that it’s more likely that the black hole in M87 is 6.6 billion Suns. And this is remarkable to me!
Not the 3% increase over what we previously thought; obviously that’s not such a big deal. But the fact that we are making new observations, and our conclusions, our results, what we understand these objects to be are hardly changing at all! In other words, we really think we’re getting it right.
But that doesn’t mean there aren’t surprises out there.
Typically, the biggest galaxies (like M87) have the biggest black holes; a galaxy like ours is only 0.2% the mass of a monster like M87. And unsurprisingly, our black hole is only around 3 million solar masses, rather than the 6 or 7 billion that M87 has.
But up above is the relatively close-by galaxy, Heinze 2-10. A small, irregular galaxy with no well-defined core or bulge, it’s often compared to the Large Magellanic Cloud (LMC), one of the small satellite galaxies slowly being dragged into our Milky Way.
The LMC doesn’t have a large jet, a central bulge, a fast-moving disk, or flares of gas coming from it at all. In fact, we’ve just kind of always assumed that you needed a large central bulge where big stars live, die, and merge together to make and grow a supermassive black hole.
But Amy Reines and her team took a closer look at Heinze 2-10, and what did she find?
Not only is there a black hole there, it’s much bigger than we’d have expected: about one million Suns! What does this mean? Does it mean, as some speculate, that black holes form early on, and that galaxies often form around them?
Very, very unlikely. That would contradict what we know about structure formation. What’s the much more likely explanation?
With billions of galaxies in the Universe, and billions of years for each of them to evolve, there is a great diversity among them. It’s not like we found a billion solar mass black hole there; it’s that we found a black hole a third the size of ours in a galaxy about a tenth the size of ours.
We’re learning more about what’s possible, and that’s important. We’re learning that you don’t need a current central bulge to form a massive black hole, but that doesn’t mean there wasn’t one in the distant past. The Universe, remember, is a violent place.
But what does this mean for the largest black holes?
Overall, you’d still want to look to the largest galaxies for them. And this guy, IC 1101, is the largest galaxy ever discovered in the Universe, at more than 100 times the volume of supermassive M87!
With over 100 trillion stars, and an estimated mass a quadrillion times our Sun, that’s the horse I’m betting on for the largest black hole in the Universe. We haven’t found it yet, mostly because it’s over a billion light years away, but with a black hole speculated to be tens of billions of times more massive than our Sun, that’s the best scientific guess we’ve got!
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] and even though I just turned 12 I can understand all of it and I’m interested, I could almost copy-paste and hand it in as mine [don't worry I won't im not a plagiarist] … oh and could you possibly reply to “Napoleon” to watch his language and that only a primal beast lacking many human intelligence functions would refrain from using full sentences in that manner. Really.
