Star eaten by a black hole: still blasting away

By Phil Plait | August 26, 2011 6:30 am

In late March of 2011, an extraordinary event occurred: a black hole in a distant galaxy tore apart and ate a whole star (I wrote about this twice at the time; here’s the original post, and a followup article including a Hubble image of the event).

Now, there’s more info: the black hole, lying at the center of a galaxy nearly 4 billion light years away, has about 8 million times the mass of the Sun. When it tore the star apart, about half the mass of the star swirled around the black hole, forming twin beams of matter and energy that blasted outward at a large fraction of the speed of light. The folks at NASA’s Goddard Space Flight Center made a great animation to show this:

The star was ripped apart by tides. The thing about black holes is, they’re small: this one was probably about 15 million kilometers across. A typical star is about a million km across (the Sun is 1.4 million kilometers in diameter, for comparison). This means the star could get really close to the black hole, and that’s why it was doomed. The force of gravity drops with distance, so as the star approached, the side of it facing the black hole felt a far greater force than the size facing away. That stretched the star, and the stretching increased as the star got closer. At some point, the force was so great it exceeded the star’s own gravity, and it could no longer hold on to its material. The black hole won — as they usually do.

The material from the shredded star formed a disk around the black hole, and near the center heated up to millions of degrees as it swirled around at near the speed of light. For reasons not entirely understood, this forms the beams of matter that jet away from the hole, and as it happens one of these beams was aimed pretty much right at us (not to worry, though, since at that vast distance the light was so diminished it took Hubble to see it in visible light at all). That’s what alerted us to the event in the first place; it was detected by the Swift satellite, which was designed to look for high-energy blasts from space.

Normally, things like this fade pretty quickly, but in this case, amazingly, it’s still pouring out energy and will probably be detectable even into 2012. That is partly due to relativity: because we’re looking straight down the beam of material, we see its clock ticking more slowly. This effect works better when the material is moving at high speed, and radio observations show that the blast is still expanding away from the black hole at half the speed of light! And that’s after it slowed down by ramming into material floating in between the stars in that galaxy. It started out moving at more than 90% the speed of light.

The energy it takes to do this is mind-numbing: we’re talking about roughly an octillion tons of matter screaming outward at well over one hundred thousand kilometers per second!

It literally makes the hair on the back of my neck stand up. I’m glad this happened billions of light years away.

Astronomers will continue to observe this event to learn more about it. It probably happens all the time in the Universe, but this is the first time we’ve had the equipment to really get a good look (even if we have to crane our necks a bit from 4 billion light years away). We’re not really sure how often something like this happens, or how it affects the galactic environment. I’ll note I’m not terribly worried about it happening in our Milky Way (we have a 4 million solar mass black hole in the center of our galaxy), since, after all, we’re here. If this happened often enough to be dangerous, we wouldn’t be here to talk about it!

But it might make an interesting movie plot. Hmmmmm…

Credits: Video: NASA; Artist’s illustration of star and black hole: NASA/CXC/M.Weiss.


Related posts:

- Astronomers may have witnessed a star torn apart by a black hole
- Followup on the star torn apart by a black hole
- Most distant object ever seen… maybe
- Cosmic X-ray blast temporarily blinded NASA satellite

CATEGORIZED UNDER: Astronomy, Cool stuff, Top Post

Comments (64)

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  1. Pete Jackson

    BBBUUUUURRRRRPPPP!!

  2. Steve

    “The thing about black holes is, they’re small: this one was probably about 15 million kilometers across. A typical star is about a million km across.” Did you mean the black hole is 15 km across?

  3. Matt

    I think you’ve got the numbers for the size of a black hole mixed up. Do you mean 15 km across instead of 15 million km? 15 million doesn’t seem “small”.

  4. Yoweigh

    “The thing about black holes is, they’re small: this one was probably about 15 million kilometers across. A typical star is about a million km across (the Sun is 1.4 million kilometers in diameter, for comparison).”

    Something’s not right here…. how big is the black hole?

  5. A. Gray

    Just one point you missed – the black hole didn’t tear apart and devour the star in March 2010, that’s just when the energy from the black hole’s relativistic jets hit our telescopes. The real action happened over *4 billion* years ago!

  6. Chris

    Phil you may want to check your math. The Schwarzschild radius of the sun is 3 km. 8 million solar masses would have a radius of 24 million km, and since you are talking about across the diameter would be 48 million km. Also the animation seems to have the black hole too small relative to the star.

  7. ShavenYak

    I’m figuring up the Swarzschild radius for 8 million solar masses to be roughly 24 million km, which would make the black hole about 48 million km in diameter?

    eta: @Chris – Jinx.

  8. Beau

    Don’t listen to all these people trying to use “math,” Phil. Feel free to use any numbers you like!

  9. Carey

    Jumping aboard the pedantry bandwagon…

    Third paragraph: “The force of gravity drops with distance, so as the star approached, the side of it facing the black hole felt a far greater force than the size facing away.”

    I think you mean the “side facing away”.

  10. This was not intended to be a factual statement

  11. Mark

    It sure would make an interesting movie, but how the hell is Bruce Willis going to drill through a black hole?

  12. Dennis

    There are two common statements about black holes that have always confused me:
    “Nothing can escape a black hole, not even light.”
    “Black holes emit jets of… (gas, matter, radiation?)”
    (not directly quoting anything specific, just repeating what I recall from watching a lot of Discovery Networks programming)

    Can you explain to a layman, who only knows what he’s learned about astronomy and cosmology from watching TV, how these two, apparently conflicting, statements can be reconciled?

    I did notice this phrase in the above article: “For reasons not entirely understood…”
    But, maybe the very common statement about nothing escaping black holes needs to be amended?

    Thanks.

  13. FoxtrotCharlie

    In the same way a chocolate cupcake cannot escape a 6 year old boy, think of the jets as the burp the kid does after eating the cupcake.

  14. John Dodds

    Question: Does the amount of energy radiated out at the poles equal the amount swallowed as mass?. Is this the ultimate proof that E=mc^2? Is there proof that it is also reversible? M–> E? Electron pair production??

  15. Fingers McGee

    @Dennis,

    I’m not sure, but I don’t think these things are emitted from the centre of the black hole, but at some distance from it where matter and light can still escape the gravitational pull of the black hole. Due the heat created by material being pulled towards the black hole in an accretion disk a large amount of radiation is given off by the material approaching the black hole prior to it going beyond ‘the point of no return’ (or event horizon).

  16. blf

    Dennis:

    I’m not a physicist but I think the idea is that the matter that escaped came juuuuuust close enough to the Event Horizon to be accelerated and flung away instead of being swallowed by the black hole.

  17. Naked Bunny with a Whip

    Dennis, the jets being discussed here are generated by gas rapidly rotating around the black hole outside the event horizon. It hasn’t actually fallen in yet, so we can still see it.

    The part that isn’t fully understood is how the rotating gas creates jets of radiation.

  18. Fingers McGee

    @John Dodds

    What’s going on here isn’t matter being converted into energy.
    Instead it is Gravitional Potential Energy bring converted into heat (via friction within the accretion disk) and then emitted as electromagnetic radiation.

  19. Naked Bunny with a Whip

    15 million doesn’t seem “small”.

    For an object containing the mass of 8 million Sols, it is.

  20. Chris

    @ Dennis
    Yes nothing ever leaves a black hole. Specifically once it passes the event horizon (Defined by the Schwarzschild radius) it’s in there forever.

    Now as for emitting jets. Most if not all black holes are spinning. As matter falls in, conservation of angular momentum causes an accretion disk to form. (Almost looks like an early solar system) Now remember this disk is composed of plasma (highly charged). You have charges moving around, they cause a magnetic field mostly a dipole and the plasma can shoot up the north and south poles. Now the interactions are highly complex (magnetohydronamics I believe) and it’s hard to model. But the physics is relatively (pun intended) understood.

  21. P-A

    FoxtrotCharlie: A chocolate cupcake CAN escape a 6-year old boy. Just not in a way plesant for the surroundings (although the jets here are probably not very plesant for the surroundings either). :)

    But I must say that this was probably one of the coolest black-hole animations I have seen. Really mindblowing.

  22. Interesting article as always Phil, Denis does bring out a good point (spraying water from a fire hose into an ordinary kitchen drain would be the answer) but I have problems with that. Oh I’m sure that a star was swallowed and not flung into space riding the event horizon just right because then the star would remain whole. Once gravity sucks just a minute particle of the star – you know it’s going to get sucked up completely. Why it then spews out north and south pole of the spehere (black hole) has to be cause and effect and maybe we just don’t know what is the cause once it all gets down to a singularity.

    I’d love to see you, Phil, do a continuance of this article – it would make a fantastic Bad Universe series.

    Btw: what’s with the MUSIC box in the video? – I must have moved it around all over the place but got nothing, no popcorn, no bling, no refund.

  23. Meanwhile,reporters on site at the GRB 110328A event say that local astronomers have detected the creation of a new planet in the Milky Way Galaxy that appears to have the potential for supporting life. Scientists were quoted as saying “This planet orbits a star called the ‘Sun’ at about 93 million miles,which puts it in the habitable zone for life as we know it”.

  24. Tom

    I recently watched a discussion about black holes on some Science channel show (PumpkinChunkin into Black Holes or something). The physicist talked about what an observer just outside the Event Horizon would see as he watched someone else falling into the black hole. If I remember correctly, the gravitational time distortion would mean that, to the outside observer, the person falling in would be frozen in time. You could leave and come back again and the guy wouldn’t have moved from the observer’s perspective. Meanwhile, time would proceed along at the regular pace for the person falling in…he’d be torn apart in a nano-second.

    Anyway, if this was true, how can it be that we see the result of this sun falling into the black hole? Did it happen a really really long time ago? I recognize that it is 4 billion light years away, but did it actually happen many billion years before that even (i.e. say, 12 billion years ago?)

  25. Jon Hanford

    A possible second example of a tidally disrupted star, dubbed Sw J2058+05, was recently discussed in a paper on arXiv: http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.5307v1.pdf

    It will be interesting to see how common (or not) these events turn out to be [I'm referring here to how often we here on Earth will see stellar tidal disruptions, not necessarily their true prevalence in our universe].

  26. Wzrd1

    Christ @21, not ENTIRELY correct. Hawking radiation leaves the black hole’s event horizon.

    As for the jets, one thing to consider is, as the star (or anything else, for that matter, but in particular the star) is spaghettified, ionized gas is accelerated toward the event horizon. Ionized gas is already, quite excited, it gets even MORE excited as it’s accelerating and compressing in its flow toward the event horizon.
    Plasma that is that excited, moving relative to magnetic fields is going to conduct, generating its own magnetic field and electrons are going to ride the field lines in their own specialized spiral, emitting electromagnetic radiation as well. The path of the radiation is going to be bent by the black hole as well.
    It shouldn’t be too difficult to model on a decent supercomputer.
    I’m willing to bet that it’s at least PART of the cause of the jets.

  27. Chris

    @Tom 25
    The burst we’re seeing comes from much farther out than the event horizon where time would appear to stop. I like how the background stars are shown to be gravitationally lensed. Notice in the animation where the black hole is and where the star gets torn apart. Time is running relatively normally there.

  28. Keith Bowden

    So… in real time, how quickly was the sun actually consumed? Hours? Days? Years? Millennia? I’m so used to cosmological events happening slowly (by human reckoning), but this sounds like it was a faster process.

  29. Chris

    @27 Wzrd1
    Hawking radiation is when a pair of virtual particles are produced near the event horizon, one falls in and the other leaves taking some of the black hole’s energy (and mass) with it. Also the temperature of a black hole this size would be about 8 femtokelvin, not a lot will be emitted at this stage. However when you fall in, there is no information that can leave the black hole letting the outside world know what you were made of. Just how much mass you had. The “No hair conjecture”. So still once you go in, you ain’t getting out.

  30. mike burkhart

    Hey I think I see the USS Cygnus!Just kidding. Some people think Black Holes could make perfict trash cans . Just dump grabage into them and it will never been a problem again. I have a problem littering space but I have said in the past that we should dump nucler waste into the Sun . I think Phil might disagree knowing his commitment to the enviorment. This star could now be in another universe if the Black hole-White Hole conection theory is right (or it may be in some other part of our universe).

  31. Naked Bunny with a Whip

    @mike burkhart: I think the main environmental concern about dumping nuclear waste into the sun is the part where the rocket launching it might explode high in our atmosphere. It sure as heck won’t hurt the sun any.

    I doubt it’s cost effective, anyway.

  32. Legion

    math… pfeh! we ALL know that most black holes are 15 floobities across!

  33. Chris

    @Mike 31
    Actually my using black holes as trash cans, you can steal some of the black hole’s angular momentum. The garbage truck dumps its load as it makes a loop around the black hole, garbage goes in, truck comes out faster, collect the momentum once it comes back, power generation. Theoretically 100% efficient.
    http://www.guidetothecosmos.com/present_stars.htm

  34. Dennis

    Thanks for the explanations everyone.
    The phrasing that I’m used to hearing is, “Black holes emit jets of…”
    Maybe it would be less confusing (to folks like me anyway) if the concept were expressed in a more semantically clear way.
    E.g. – “The forces surrounding a black hole cause jets of matter that has yet to cross the event horizon, to be emitted from its poles.”
    Or some-such.
    The typical phrasing seems to imply that the jets are emanating from within the black hole, whereas the explanations given make it clear that that is not the case.

    As long as I’m picking-nits, and regarding #29 Keith Bowden’s question; One thing that has always bugged me about the TV shows I watch concerning cosmology, is that when they show animations depicting grand cosmological events – for example, the formation and movements of galaxies, the formation of nebulae, stars going super nova, etc. – they only very rarely give a context of time scale – the above animation included.

    I would like to see such animations include a caption indicating elapsed time.

  35. Robin

    The pole in this case is the axis about which the black hole (if it has angular momentum) and the accretion disk spin. While the accretion disk can be thought of as being flat, the event horizon is surface that’s quasi-spherical, so those jets have to emanate outside of the event horizon, since as others before have mentioned, nothing can escape a black hole.

    Time scales would be tough to fix on, for example, a star eventually being torn apart and digested by a black hole because you wouldn’t enough information to fix a time scale. You just cannot fix the initial conditions of the actual process.

  36. Mephane

    “It literally makes the hair on the back of my neck stand up. I’m glad this happened billions of light years away. ”

    Well you can expect the same thing happening only some ~40,000 ly away, when the black hole at the center of this galaxy swallows a star, too. The question is, when, or better yet, when we can observe it that precisely. It might happen right now without us seeing, we were lucky the particle jet of that distant black hole happened to be pointed towards us, just imagine how often this process occurs where the cannot observe the jet and thus don’t notice at all…

  37. Regner Trampedach

    Wzrd1 @ 27: I think you mean ionized and not excited. The charge of an ion only depends on how ionized (how many electrons it has lost) – not on the energies (excitation level) of its remaining electrons. The charge is what makes the plasma get accelerated along magnetic field lines, – and is what makes those magnetic fields in the first place.
    mike burkhart @ 31: The problem with “…dump[-ing] nucler waste into the Sun.” is not pollution of the Sun – I mean, that is silly to the power of 30! (and I believe Phil would agree). The problem is cost and risk (rocket failure => explosion scattering highly radioactive waste). I have seen launch costs of US$10-25,000 per kg. According to Reuter’s “factbox-Key facts on radioactive waste”(Google it): “There are about 270,000 tonnes of spent fuel in storage worldwide”. That gives us a lower range of cost of US$2.7 trillion. That little expenditure definitely makes nuclear energy cheaper than wind, solar, geothermal and biogas…
    @ various: The star is getting tidally disrupted well outside the black hole – both in reality and in the animation. The inside of a black hole normally refers to inside the event horizon (at 1 Schwarzschild radius, R_S). The singularity is a singular point at the center of the black hole, and hence shielded from our spying eyes by the event horizon. Hawking radiation is the only thing that (effectively) escapes the clutches of the event horizon (see Chris @ 30) – Only black holes less massive than about 0.6 lunar masses, will be net emitters – heavier ones will be overwhelmed by incoming cosmic background radiation (at 2.725K). The accretion disk ends about 6*R_S from the singularity where orbits become unstable and plasma plunges directly into the black hole. The jets are launched from the accretion disk and aligned along the rotation axis (not emitted from the poles!), but the details of the mechanism are not quite worked out yet (magnetic fields are most likely involved). The actual tidal disruption of the star forms the very outskirts of the accretion disk. So all of this happens fairly far away from the event horizon (although far too close for comfort!!!).
    Chris @ 21: and general relativistic magnetohydronamics at that!
    Cheers, Regner

  38. DrFlimmer

    @ 37 Mephane

    Well, if the jet is not pointed at out direction we could potentially still see it. Radio observations would definitely reveal it. However, since radio observatories do not make for good alerts, we need high energetic radiation to be detected by our flying observatories (mainly x- and gamma-rays).
    What could that be? Ah, the accretion disk. The matter will get fairly hot, shining brightly in UV and probably also in X-rays. This could alert us to such an event, even without the jet pointing towards us.

  39. Thameron

    @31. mike burkhart

    If the mass that falls into a black hole were exiting somewhere else then it stands to reason that the black holes would be getting less massive and I don’t think they are. I don’t think that mass is going anywhere.

    To my knowledge there has been no actual proof of the existence of Hawking radiation. I’ll wait for that before giving it credence.

  40. My math concurs with Chris’ math. I calculate that an 8-million-solar mass black hole would be 47 million km across, which is close enough for a rough estimation.

  41. Wzrd1

    @30 Chris, you are correct. Anything entering the event horizon isn’t returning intact. However, one interesting side effect of the math is, once through the event horizon, one would take an infinite amount of time, relative to the rest of the universe, to reach the singularity. In essence, the matter just beneath the event horizon is essentially forever at that point. Hence, the virtual particles should be radiating past the event horizon and lost to the singularity.
    Of course, the amount is still miniscule compared to the amount absorbed by the black hole in the first place, so large mass singularities are in no real danger of evaporating during the life of this universe.
    Only small singularities, typically sub stellar mass ones would evaporate quickly. IF it’s possible to generate one, which is dubious under most normal circumstances in the universe.

  42. VinceRN

    In late march of 3,999,997,989 BCE (or so)…

  43. Wzrd1

    @VinceRN, I remember that day! It was horrible!
    The beer was hot, the women were cold. It was HORRIBLE!
    I could get by on the hot beer, but… ;)

    Hey, in the morning, these days, it FEELS like I’m that old.

  44. Messier Tidy Upper

    Great animation. Eerily silent, graphically beautful and very thought provoking. :-)

    Great write up too. Thanks BA. :-)

    @29. Keith Bowden :

    So… in real time, how quickly was the sun actually consumed? Hours? Days? Years? Millennia? I’m so used to cosmological events happening slowly (by human reckoning), but this sounds like it was a faster process.

    It does, but I’m not sure myself. I second the question & agree a timescale for the animation would be great too. Going by the description :

    “Normally, things like this fade pretty quickly, but in this case, amazingly, it’s still pouring out energy and will probably be detectable even into 2012.”

    It sounds like it just takes months to years but this really isn’t clear at least not to me. :-(

    @ 41. Arik Rice & others asking about /calculating the Black Hole’s size :

    My understanding is that a stellar mass black hole is tiny – smaller than a city – but a supermassive black hole can be as large as our solar system. This one’s a supermassive galactic core variety of BH so it could be reasonably large. Sadly, I’m hopeless at maths so I’m not going to attempt to calculate it myself and that range hardly narrows it down much but still.

    @20. Naked Bunny with a Whip : “For an object containing the mass of 8 million Sols, it is.”

    [Nit-picking pedant.] But a Sol means a martian day and even 8 million Sols would therefore not have any mass – only time! ;-)

    Don’t you mean 8 million solar masses? ;-) [/Nit-picking pedant.]

  45. srinivasvr

    ego here i go…

  46. Svlad Cjelli

    “Don’t you mean 8 million solar masses?”

    A “solar” mass is a “solar” mass because it is the mass of a “Sol”. “Sol” is not a measurement, but a named physical object.

  47. VinceRN

    @ 47 Dirk Gently – “Sol” is simply Latin for “Sun”, it is not the name of the the Sun. We also use Helios in talking about the Sun, being the Greek word, but that’s not the name of the Sun either. Solar is used as the adjectival form probably because Sun, being a Germanic would would become Suner or some such as an adjective and just not sound right.

    Time on mars is measured in solar days, and those days are sometimes referred to as sols, but I think that is colloquial, not really official. I could easily be wrong about that though.

    My source is the IAU, who are the official namers of stuff in the sky. They refer to it as the Sun, capitalized, from which I conclude they are using Sun as a proper noun, and that makes it’s official name the Sun. Personally, I’d prefer it be officially called Helios, but I don’t get invited to those meetings.

  48. As others have said, it would be nice to know how long this takes on a human time scale.

  49. Mark

    @Phil – This article says 2010, but the original article says 2011 and was written in 2011. I think you’ve got a typo.

  50. Mark (50): Yup, thanks!

  51. John

    Mmmmm star matter. I wonder what it tastes like.

  52. icemith

    So, which is the “sunny side up”, Sonny?

    Ivan.

  53. Juan

    @48 VinceRN:
    “Dirk Gently”, great catch!
    See, I’d completely forgotten what his real name was.
    Kudos, sir.

  54. Svlad Cjelli

    48. VinceRN – Nothing you said contradicts that a solar mass is solar because it is the mass of a Sol.
    Nothing you said contradicts that Sol is a physical object.
    Nothing you said contradicts that the object is called “Sol”, anymore than it does that a Bad Astronomer is a Phil.
    Nothing you said contradicts that 8 million specimen of the object would have 8 million times as much mass as a single specimen of the object has.

    :

  55. Mike

    So a bunch of folks here have been implying that the accretion disk and the rotational axis of the black hole itself line up. Is this actually the case? If a star came shooting in on a polar orbit to the black hole, would the accretion disk form that way, or would the black hole somehow drag the gunk around to be in line with the black hole’s equator?

  56. @ Dirk #53 – Here is what contridicts it: Phil is named Phil officially, he likely has a piece of paper assinging him that name from the official organization that names young hairless apes of his particular lineage (his parents), and that paper likely bears a sealed of approve from the relevant government agency. You could call him Bob, and if enough people did he would come to be recognized as Bob, but he would still be Phil. The Sun is officially called the Sun by the only organization that officially names such things. You can call it ‘Sol’ and I can call it ‘Yellow’s and most will know what we are talking about. However, it will still be the Sun. Sol is not the name of any physical object in any official way, it is not used in Science or Academia anywhere as far as I can tell. The fact that science fiction writers like to refer to it that way is meaningless. Also a ‘sol’ as a shortened form of ‘solar day’ in reference to Mars really is a measure of time, and is in fact used in Academia and Science.

    Ain’t it fun to be pedantic over something so totally meaningless as this? Call it Sol, the Sun, Helios, or that big yellow thing that peaks through the clouds and causes traffic problems hare in the Pacific Northwest. Who really cares?

  57. Svlad Cjelli

    You, apparently.
    The referent is the same, and you still aren’t saying that the signifier doesn’t refer it, so I don’t see the point of contention here. If I ever implied that the Intergalactic Council of Pastry has baptised the star Urkel and burned the Steve-heretics, that wasn’t my intention.

  58. Frank Sellers

    Why is this story in the “Bad Astronomy” section? Is it because the black hole was acting ‘bad’ly? I thought this section was for faulty science.

    And yes, 15 million km doesn’t seems “small” to me, either.

  59. Jeremy P

    @Dennis

    so nothing can escape a black hole, but a black hole can, theoretically, evaporate. ha ha, I love science!

  60. SurDin

    @1-7, Phil.

    I found what’s the typo. The SS-Radius is 15 million *Miles* ~=24 Million KM. :)

  61. martin

    15 million is small for a black hole

    YES it is 15 million becuase generally to have anything smaller requires a theoretical micro black hole etc

    you cant have a star thats much smaller than 1.8 or so solar masses so the smallest would be about 1.3million or so

    anything like 15 km would eat its way up in minutes if it fell into a star. munching its way through in a nice cylyndrical path

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