NuSTAR catches a black hole’s hot belch

By Phil Plait | October 23, 2012 1:33 pm

Our Milky Way galaxy is a sprawling collection of gas, dust, and hundreds of billions of stars, arrayed in a more-or-less flat disk. In the very center of the galaxy – just as in countless other large galaxies like ours – lies a hidden monster: a black hole. And not just any black hole, but one with four million times the Sun’s mass.

It’s called a supermassive black hole for a reason.

Usually, it’s not doing a whole lot except sitting there being black and holey. But sometimes it gets a little snack, and when it does it can let out a cosmic-sized belch. A very, very, very hot belch. Like it did in July 2012:

[Click to schwarzschildenate.]

These images were taken with NASA’s newest X-ray satellite, NuSTAR (more on that in a sec). NuSTAR can detect high-energy X-rays coming from space, and happened to be pointed toward the black hole when it erupted. On the left is an overview of the region near the center of our galaxy. The whitish area is the stuff immediately surrounding the black hole (the pink glow is most likely from a supernova, a star that exploded in centuries past). On the right is a series of three images showing that region getting very bright in X-rays, then fading away: a flare.

OK, so I know what you’re thinking. How can a black hole – famous for gobbling down everything nearby, even light – get bright and emit so much energy?

Basically, it doesn’t. The stuff around it does.

A black hole by itself is dark. But if a gas cloud gets near, very interesting things happen. The gravity from the black hole stretches out the cloud, because the part of the cloud nearer the hole gets pulled by the gravity harder than the part of the cloud farther away. Also, the cloud probably doesn’t just fall straight it; like an orbiting planet around the Sun it has some sideways motion. This means the hole whips it around, pulling out a long tendril which then spirals ever closer to the Point Of No Return.

This video may help. It shows a star getting torn apart by a black hole, but the principle is the same.

So some of the stuff may get flung away, but a lot of it falls toward the black hole. As it nears the hole, it forms a flat disk, called an accretion disk. The material in this disk is tortured by unbelievable forces: the inner part of the disk is whirling madly around the black hole, while the outer part is moving more slowly. The gas is literally heated up by friction as the different parts of the disk rub against each other (other forces like magnetism play a role too). The heating can be HUGE: the gas can reach temperatures of hundreds of millions of degrees!

Gas that hot emits X-rays, which is how this flare was seen by NuSTAR. Probably, a smallish cloud found itself too close to the black hole, got torn apart, and flew down into it. As it did it got extremely hot and blasted out X-rays. But when the whole thing was gobbled down, the X-rays stopped… because there was nothing left to emit them.

So maybe saying this was a belch is a bit misleading, since you do that after you eat something. This is more like your food screaming loudly and incoherently and flailing around while you’re actually eating it. Is that better?

This is a pretty cool observation. For one thing, our local big black hole is usually pretty quiet, so even getting a chance to see something like this is pretty nifty. Second, it can tell us what the environment is like near the black hole. And also, it helps us understand what happens right before some unfortunate object takes The Final Plunge. As I mentioned, every big galaxy has a supermassive black hole – ours is actually rather paltry compared to others; the one in the center of the Andromeda Galaxy is probably ten times more massive than ours – so anytime we can observe something going on with ours, we learn more about how they behave in other galaxies, too.

Also, I’m proud of NuSTAR. I worked on the project for a while, as part of the Education and Public Outreach team. I wrote quite a bit about the mission at the time, and was very pleased when it launched in June. It almost never got off the ground; the mission was actually canceled at one point, but was eventually reinstated.

I’m very glad it was! Now we can watch black holes in our galaxy (and others) as they eat and act rudely. Maybe it’s impolite to stare, but c’mon. When one puts on a fun show like this, it would be wrong not to.


Related Posts:

- Astronomers see ANOTHER star ripped apart by a black hole! (including this original post and this followup)
- NuSTAR opens its X-ray eye
- The long reach of the Centaur’s dark heart
- Desktop Project Part 22: A black hole belches out a hurricane

Comments (41)

  1. Chris

    OK, so I know what you’re thinking. How can a black hole – famous for gobbling down everything nearby, even light – get bright and emit so much energy?

    No, you don’t know what I was thinking. I knew about accretion disks when I was in grade school. It was the first thing which popped into my head. You are not psychic, Phil.

    Nom, nom, nom :D

  2. Chris

    > So maybe saying this was a belch is a bit misleading, since you do that after you eat something. This is more like your food screaming loudly and incoherently and flailing around while you’re actually eating it. Is that better?

    So you’re saying that the Black Hole is really the Tazmanian Devil?

  3. ErisWolf

    Science! Black Holes! Stars! Atoms! Solar Flares! 1st class awesomeness! Come ON America!

  4. ErisWolf

    We gotta hand it to Bad Astronomy! Awesome!

  5. ErisWolf

    This is SO cool. ” lies a hidden monster: a black hole. And not just any black hole, but one with four million times the Sun’s mass.It’s called a super massive black hole for a reason.
    Usually, it’s not doing a whole lot except sitting there being black and holey. But sometimes it gets a little snack, and when it does it can let out a cosmic-sized belch. A very, very, very hot belch. ” 1st class awesomeness

  6. Matt B.

    “The gas is literally heated up by friction as the different parts of the disk rub against each other…”

    Not to mention that tearing a star apart exposes the inner material that’s already at millions of kelvins.

  7. Francisco (FC)

    Doesn’t this mean that the flare occurred some twenty thousand odd years ago?

  8. DrBB

    our local big black hole is usually pretty quiet, so even getting a chance to see something like this is pretty nifty.

    I was thrilled when I saw that this was our own galactic core not somebody else’s (who cares about them?). But I gather that, if you’re a living creature, the last thing you want to live in is a galaxy where this kind of thing and worse is happening all the time, i.e., a supermassive b.h. that’s gobbling down stuff with great enthusiasm and blasting out vast beams of radiation that can sterilize the whole spiral (or whatever shape yours happens to be).

  9. Satan Claws

    Going off on a tangent apropos black holes’ “jets”, I imagine that it’d be interesting to find out how that star matter distributes (in the numeric simulation in the video) if the star collides with a *rotating* black hole — what changes it’d make to the distribution of the ejected star matter. The clip’s site makes no mention of rotating black holes, so I assume they assumed a non-rotating BH in the collision simulation.

  10. Crudely Wrott

    This observation actually does deserve to be described as awesome. It certainly makes me feel small and insignificant.

    It’s like staring at some great beast that sleeps, has been sleeping without stirring. You gaze at it, unable to look away, aware of its unparalleled power, fearful of its nature, imagining that it has dreams made of dark intents.

    Without warning its eye opens and a baleful fire is revealed as you realize it is staring back and its gaze looks within you, through you, and you know it hungers. Now you know the fear that has no comfort, no escape. Then you are falling and the great, dead eye grows as the fire flares and reaches . . . closer . . . closer . . .
    (shudder)

    Something else that’s very close to awesome is that we are looking not through a lens like that of a camera but through a bundle of nested, conical, metal tubes. NuSTAR is an inspired design, a pinnacle of expertise, a physical testament to the power of mind. And, it’s still brand spanking new! More revealing wonders are surely in the, ahem, pipeline. I’ll be staying tuned.

  11. DrFlimmer

    Hey Phil,

    you could have mentioned that there is another suicide cloud on its way to the SMBH and due to come close to it in roughly a year. THEN we can point our telescopes there and can see the whole thing! This is going to be awesome!

  12. amphiox

    And to think the Milky Way’s super massive BH is actually a runt within its own class. Most galaxies the size of the MW have much bigger SMBH’s. Andromeda’s is 20 BILLION solar masses.

  13. Dee

    Sounds like it is more like a black hole sucking in a piece of spaghetti with sauce on it. As the spaghetti get sucked in, it twirls and sauce flies everywhere (what we are seeing).

  14. DanM

    If only there were such a thing as *good* x-ray optics… think of what they could do THEN.

    (says the optics guy, who feels a little smug that HIS mirrors are better than 99% reflectors. Take THAT, x-ray people!)

  15. Dr.Feelgood

    @Francisco (FC), yep, although that’s generally just assumed when you give the light year distance and talk about something happening in the present with regard to astronomy. Pretty crazy that something within our galaxy is THAT far away.

    And then, conceptualizing what 100,000,000 degrees would be like…mind boggling. I can’t picture any atomic structure surviving that kind of torture.

  16. @7. Francisco (FC) asked : “Doesn’t this mean that the flare occurred some twenty thousand odd years ago? “

    Technically yes, although we usually think of and record it as happening now ignoring the light travel time delay. Same a show we call supernovae and novae by the year

    Spectacular, good news this – and looking forward to the hearing more when the cloud (#11.) DrFlimmer mentioned hits. 8)

  17. Georg

    If only there were such a thing as *good* x-ray optics… think of what they could do THEN.

    For this some matter would have to exist with some refraction to x-rays.
    This in turn would quench all the x-rays coming from the galactic center.
    Either You want x-rays to penetrate any kind and amount of dust, or You
    want some “optics” material for x-rays.

  18. @14. Typo fix – make that:

    Same as how we call supernovae and novae by the year they appeared in our skies not when they technically exploded.

  19. Stuart Bradley

    “So maybe saying this was a belch is a bit misleading, since you do that after you eat something. This is more like your food screaming loudly and incoherently and flailing around while you’re actually eating it. Is that better?”
    Quote of the year.

  20. Scott P.

    “For this some matter would have to exist with some refraction to x-rays.
    This in turn would quench all the x-rays coming from the galactic center.”

    Only if this matter existed in natural form.

    I think the key to refracting x-rays is transparent aluminum.

  21. Gamma ray refraction has been demonstrated. Pretty weak so far. But gamma ray telescopes may be possible after all.

  22. Wzrd1

    @Phil, any approximate energy measurement on that burst? Duration of the burst?

    @DrFlimmer #11, quite true. A few other clouds are heading toward the core as well, as I recall. It’s surprisingly crowded in close!

  23. Jon Hanford

    Andrea Ghez’s Galactic Center Group has produced a short animation showing Sgr A* undergoing an outburst (in infrared light): http://www.astro.ucla.edu/~ghezgroup/gc/pictures/lgs05_movie.shtml

  24. Blathering Blathiscope

    It may be impolite to stare, but its rude to chew with your mouth open.

  25. Ed

    I was wondering: where in the sky is the galaxy center? I mean, in which constellation? I suppose that it’s somewhere in the milky way, but in which part? And I guess it would be visible from the southern hemisphere. (I live some 10km south of the Tropic of Capricorn.)

    It’d be incredibly nerdy to point to the night sky and tell my friends: the center of the galaxy is that way!

  26. Doccus

    A little confused about the distances here.. If we are about 26,000 light years from the center of the galaxy, how could this event have happened only 10,000 years ago, as a couple of commenters have observed..
    At least this comments thread is a lot better than the last time you posted on a black hole’s diet ;-)

  27. Matt B.

    @25 Ed – Sagittarius.

  28. Ed

    @27 Thanks, Matt!

  29. amphiox

    Technically yes, although we usually think of and record it as happening now ignoring the light travel time delay. Same a show we call supernovae and novae by the year

    Since information moves at the speed of light, so does causality. From our frame of reference, things happen when the information about them happening reaches us, ie, in our frame of reference, it happens when the light reaches us and we see it.

    One could in theory I think talk about things as happening in their own reference frames, but that rapidly gets very, very, very complicated.

  30. Very cool! I didn’t know that astronomers had so much info on what our own ‘lil SMB was up to.
    And NuSTAR is worthy of a few posts all by itself! Seriously, if anyone hasn’t Googled NuSTAR already, do it! Fascinating stuff. Long story short, it’s very difficult to build an X-Ray telescope. There really aren’t any materials that refract X-rays like glass does for light, and X-rays tend to be transmitted or absorbed when they hit most materials at a substantial angle. The only way to focus X-rays is a design called a Wolter telescope, which uses long cones to reflect X-rays at extremely low angles. This design means the NuSTAR has to be 10 meters long to get the needed focal length. The focusing optics consist of 133 concentric shells made of 4680 mirror segments. Each mirror segment is made of many layers of alternating high and low density material in layers several atoms thick – all this is necessary to catch those elusive little x-rays!

    Also, I’m curious – does gas really get heated up by friction? Is that a process that gas even undergoes? Or is it more like when meteors or spacecraft enter the atmosphere, and heat air by adiabatic compression? I guess it’s hard to compare this situation to anything we’re familiar with, when you’ve got extremely thin gas moving at relativistic velocities.

  31. Nigel Depledge

    Joseph G (30) said:

    Also, I’m curious – does gas really get heated up by friction? Is that a process that gas even undergoes?

    Yes, because friction arises through Van der Waal’s forces, which can arise whenever two molecules or atoms get close enough to one another.

    Or is it more like when meteors or spacecraft enter the atmosphere, and heat air by adiabatic compression?

    Well, when spacecraft and meteors enter the atmosphere, the heating is mostly due to the supersonic shockwave that arises as a consequence of the object’s speed in our atmosphere. In the accretion disc of a BH, I daresay some of the heating may be due to compression, but the bulk of it seems to be friction.

  32. @Nigel Depledge: Yes, because friction arises through Van der Waal’s forces, which can arise whenever two molecules or atoms get close enough to one another.

    Ahh. I learned something today :)

  33. Wzrd1

    Actually, the gas is warmed BOTH by friction AND irradiation by x-rays from the superheated gases closer in that are warmed from Van der Waal’s forces. There can also be magnetic components to emission from ions as well.
    Let’s face it, a black hole is already complicated in and of itself, the accretion disk adds to the complicated environment.

  34. @Wzrd1: Shoot, you can probably throw synchrotron and bremsstrahlung radiation in there too :) As usual, black holes defy simple explanations…

  35. Kenneth Polit

    This is so cool! I love this site, thanks, Phil.

  36. Autumn

    I remember being in 2nd grade or so and reading “How do We Know About Black Holes?”. It was very interesting, and didn’t dumb things down too much. Still, and this was less than 30 years ago, that book still held up Cygnus x-1 ( I believe I’m remembering that correctly, and it isn’t just a Rush song) as the best possible candidate for a black hole. I don’t recall that it even mentioned the possibility of an SMBH at the center of a galaxy.
    Now we’re looking at one.
    I love science.

  37. Nigel Depledge

    @ Wzrd1 (33) -

    Interesting additional info there.

    Please note that the question I was answering was “does friction occur in gases?”. I was not attempting a complete explanation of how the accretion disc heats up. Although, reading my comment again, I can see that this was not explicitly clear first time around.

  38. Nigel Depledge

    Autumn (36) said:

    . . . Cygnus x-1 ( I believe I’m remembering that correctly, and it isn’t just a Rush song) as the best possible candidate for a black hole.

    Yes, Cygnus X-ray source 1 (Cygnus X-1) was the first BH candidate identified.

    And the Rush song was about the black hole that was suspected to be Cygnus X-1.

    Six stars of the Northern Cross / In mourning for their sister passed / In a final flash of glory / Never more to grace the night,

    (which is probably Bad Astronomy, as there is no reason to suppose any real relationship between the six bright stars of Cygnus and the Cygnus X-1 BH – does anyone know the distances to these stars and to the BH?)

    And

    I set a course just east of Lyra, / North-west of Pegasus, / Through into the light of Deneb, / Sailing ‘cross the Milky Way. / On my ship, the Rossinante (sp?), / Wheeling through the galaxy / Headed for the heart of Cygnus / Headlong into mystery.

  39. @ 36 Autumn: I remember being in 2nd grade or so and reading “How do We Know About Black Holes?”. It was very interesting, and didn’t dumb things down too much. Still, and this was less than 30 years ago, that book still held up Cygnus x-1 ( I believe I’m remembering that correctly, and it isn’t just a Rush song) as the best possible candidate for a black hole. I don’t recall that it even mentioned the possibility of an SMBH at the center of a galaxy.
    Now we’re looking at one.
    I love science.

    Hehe, I remember that too. All the space books I had as a kid mentioned Cygnus X-1 as the one “probable black hole”. And now we’re swimming in ‘em! :) Not to mention a bunch of stuff that those books I grew up with never even hinted at, like the accelerating universe, and exoplanets.
    I never knew Rush did a song about Cyg X-1. Awesome! Gonna fire up Grooveshark and see what I missed…

  40. Nigel Depledge

    Joseph G (39) said:

    . . . Cygnus X-1 as the one “probable black hole”. And now we’re swimming in ‘em!

    Erm, swimming in black holes?

    How does that work? Do you have to use quantum-butterfly-stroke?

  41. @40 Nigel Depledge: It’s definitely not for amateurs. Your arms have to exceed the speed of light on the upstroke, so it’s a pretty intense workout :D

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