Monster black hole devours dead star

By Phil Plait | January 4, 2010 9:55 am

Deep in the heart of a globular cluster orbiting an elliptical galaxy, it looks very much as if a massive black hole is in the process of tearing apart and devouring the remnant of an old star. And how do we know we’re witnessing this violent stellar demise? Black holes are messy eaters.

chandra_ngc1399

The discovery comes from the Chandra Observatory, a telescope in space designed to detect X-rays. This high-energy form of light can only be generated by violent events, things like exploding stars, strong magnetic fields, or extremely hot objects. Astronomers (including Jimmy Irwin, an old friend I went to grad school with!) using Chandra detected an unusually bright source of X-rays coming from a globular cluster — a tightly packed collection of stars — belonging to NGC 1399, a galaxy 65 million light years away. In the picture above (a combination of Chandra X-ray images and optical images from the huge Magellan telescopes in Chile), the galaxy is the bright blob on the right, and the new object — called a ULX for Ultra Luminous X-ray source — is marked with the red lines.

We know black holes exist in globular clusters, so that’s nothing new. We also know stars are so jam-packed in globulars that it’s not only possible but relative common (on a cosmic scale) for these stars to interact gravitationally. When a star gets too near a black hole, it can have matter pulled from its surface, which falls into the black hole. As it plummets to its death, it can first pile up just outside The Point of No Return, whipping madly around the hole, and heating up so violently it can emit X-rays.

That sort of thing has been seen before. What’s new here is that first, the type of X-ray emission seen from this event indicates that the star isn’t simply giving up matter slowly to the black hole; it’s actually getting torn apart, physically shredded by the vast gravity of the black hole. Second, what the astronomers have seen is that the emission is rich in the element of oxygen, but oddly missing hydrogen. Hydrogen is the most common element in the Universe, and all normal stars are almost entirely made of the stuff (the Sun is, for example). Not seeing it means the star getting eaten up by the black hole is most likely a white dwarf, the dense remnant of a dead star’s core. After a lifetime of fusing hydrogen into helium, there typically isn’t any hydrogen left in a star’s core. Once the star dies, the remaining core becomes a white dwarf, devoid of hydrogen but also commonly rich in oxygen.

So not only is this possibly the first time a black hole has been caught in the act of viciously ripping a star apart, the star itself is a bit of an oddball.

And there’s more, too. Looking at spectra taken of the object reveals how fast the material is moving as it orbits the black hole, and that in turn tells us how massive the black hole is. What astronomers found is that this particular black hole must have a mass of a thousand times that of the Sun! Because of the way black holes form, it’s common to see them have a few times the mass of the Sun, or even as much as 20 or so. We also see truly gigantic ones with millions or billions of times the Sun’s mass. But it’s recently been theorized that intermediate-mass black holes exist as well, with hundreds or thousands of times our Sun’s mass. Observations have been tantalizing about these objects, and this new evidence from Chandra adds to the idea that middle-weight black holes exist.

I think observations like this are very exciting. When a new type of object is suspected, or even found, we usually get incremental supporting evidence for them. But it’s rare to get a twofer: not only does this support the existence of intermediate mass black holes, but we caught one in the act of violently tearing apart its dead neighbor. In a hundred years or so, the last morsels of the white dwarf will fall into the black hole, never to be seen again. Not even crumbs will be left, so it’s pretty cool we were able to see this when we did.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (35)

Links to this Post

  1. Un agujero negro que devora una estrella muerta | January 4, 2010
  1. DrFlimmer

    Ah, the good season is starting! Let the big astro-news flow!

  2. NGC3314

    Cool! And the process doesn’t just happen with supermassive black holes in galaxy nuclei, too. (We just hired Jimmy Irwin, and I’m seeing this as a better and better decision…)

  3. recently been theorized

    There you scientists go again, changing your minds and coming up with new stuff…

    :P

    I love how observations and data were gathered for this new theory. It’s almost as if scientists knew what they were doing, and had some sort of reliable method for figuring these things out!

    BTW, my daughter and I were watching a show about Gamma Ray Bursts. It’s amazing to think that we really didn’t have an idea of what was causing some of them until within her lifetime! Sometimes I think people forget how recent some knowledge we have is!

  4. Jonathan Hueschen

    Hi Phil,

    Do you know if there are any tours of the Giant Magellan Telescope? I’ll be in Santiago next week and I have some spare time, would love to check the thing out.

    If you or anyone else have any contact info that would be great too, I couldn’t find much on the internet.

  5. Jason

    Everytime we talk about a black hole eating something I can’t get; om nom nom nom out of my head. In my opinion, every black hole should be making this sound.

  6. Tony

    When I read about a black hole eating a star, I can’t help but think what if there were planets orbiting those stars, and what if there was intelligent life on one of those planets. I know since this was a white drawf there was little if any chance for life on planets here, but on other occasions, would people know it was coming?

  7. Brian

    >This high-energy form of light can only be generated by violent events,
    > things like exploding stars, strong magnetic fields, or extremely hot objects.

    Or dentists. You forgot dentists. (Although come to think of it, my new dentist IS kinda hot…)

  8. /me hums the theme to Disney’s The Black Hole

    Thanks a lot for getting that stuck in my head, Phil. :-

  9. mike burkhart

    Maybe the white drawfs matter won’t be gone some think matter that gose thro a black hole goes out of this universe and into another universe (like the oppsite universe in a Star Trek episoide) in fact our doubles in that other universe could be wacthing the white drawf emerigeing form a white hole that is if our doubles are astronomers (lets face if there is a universe that is an oppisite to this one your double in that universe would be oppisite of you for example I try to stay out of trouble and am law abiding my double in the other universe is maybe serving life in prison and leads a life of crime) the matter may also be some where else in this universe . but the one this proves is that if a space ship tried to use a black hole to go some where it would not survive . In face the thing I think we could use a black hole for is to get rid of garbage

  10. costas

    If black holes don’t exist what is the alternative theory?

  11. Wayne Robinson

    “If black holes don’t exist what is the alternative theory?”

    John Moffatt (“Reinventing Gravity”) thinks they are grey stars instead. His theory of MOG (modified gravity) includes general relativity (unlike MOND), and does away with the need for dark matter too. He says MOG also is compatible with the Bullet Cluster (which was one of the “proofs” of dark matter).
    Personally, I won’t accept the existence of dark matter until it is offered for sale on ebay (with a certificate).

  12. Yeebok

    Wayne, look up Teves, a successor to MOND which far as I know includes relativity.
    http://en.wikipedia.org/wiki/Tensor-vector-scalar_gravity

  13. “Gravity is the phenomena of Mass multiplied by the Speed of Light, Squared.”

  14. Phil, it would be great if you could include links to the underlying research papers,
    for people wanting more detailed information. I couldn’t find anything on astro-ph,
    but the ADS has http://adsabs.harvard.edu/abs/2010AAS…21540410I
    which looks very relevant…

  15. DrFlimmer

    What a coincidence. I just watched an episode of a German science-TV-series named “Alpha Centauri”. In it Harald Lesch, a German astro-physicist, explains in 15 minutes a special topic of physics/astronomy, and that can be whatever you can think of.

    Well, in that specific episode (on DvD) he explains the “Silk-damping” (see here: http://en.wikipedia.org/wiki/Silk_damping ). What it basically explains is that in the early universe the “normal” matter couldn’t collapse into denser structures due to its gravity, because the photons prevented any denser structure to built up. This is one reason why the CMB is so uniform, or, the other way around, the uniformity of the CMB tells us that there were no density fluctuations in the “normal” matter after 380000 years.

    BUT we observe little differences in the CMB on the order of 10^-5, which is extremely small. This means that there WERE density fluctuations, but only very little ones. Where did they come from? They cannot be due to the “normal” matter, because the radiation always destroyed them, as described above.
    So, what is needed is additional gravity to form these potentials. Dark matter is a good candidate.

    @ Wayne Robinson: Any links concerning MOG?

  16. coolstar

    First day of the largest astronomy meeting in HISTORY with dozens of neat Kepler talks and an intermediate mass black hole is the best you can do. Geez, Louise. We KNEW intermediate mass black holes had to exist but the hot (12000K plus) planetary sized things orbiting stars as seen in Kepler data? That’s a truly unexpected result.

  17. molybdenumfist

    Black hole black hole black hole starts with B
    …but remember kids, white dwarfs are a sometimes food.

  18. Gary Ansorge

    Only 100 years to finish its meal? ,,,and we’re right here to observe that? What specular timing we have.

    GAry 7

  19. I thought white dwarf stars were composed largely of iron and nickel, as those two elements have the most tightly-bound nuclei, and are therefore unable to yield energy via fusion. How are oxygen-rich white dwarves formed?

  20. Brian Too

    Funny, 100 years seems a long time for a black hole to complete the task. A very long time. I would have guessed a week to a month, at most.

    I mean, a black hole is the classic irresistable force, right?

  21. Wayne Robinson

    “Funny, 100 years seems a long time for a black hole to complete the task. A very long time. I would have guessed a week to a month, at most.

    I mean, a black hole is the classic irresistable force, right?”

    Well, not quite. A 10 solar mass black hole is going to have the same effect as a 10 solar mass ordinary star; it’s going to have the same gravitational force on its surroundings. It isn’t going to “vacuum up” surrounding matter any more quickly.

  22. Grimbold

    I wonder what happens to the degenerate material the white dwarf is made of when the white dwarf is ripped to shreds. It will no longer be compacted by the great weight of matter above it, because that is being stripped away by the black hole; so what happens to it?

  23. Dr Cy Coe in NL

    @Gary Ansorge and @Brian Too:
    Considering that NGC 1399 is a galaxy 65 million light years away, the blackhole has already devoured the star 65 million minus 100 years ago. :)

    Come to think of it, this event must then have occured at the same time as a mass extinction event here on earth (Cretaceous–Tertiary) that is commonly attributed to a large asteroid impact. Coincidence, I think so.. :)

  24. Dr Cy Coe in NL

    (can edit, but can’t delete my own post?)

  25. StevoR

    Astronomers (including Jimmy Irwin, an old friend I went to grad school with!)

    Any relation of the Moon walker James Irwin – the 8th person to walk on the Moon with David Scott on Apollo 15? See : http://en.wikipedia.org/wiki/James_Irwin

    @ 19. Grimbold Says:

    I wonder what happens to the degenerate material the white dwarf is made of when the white dwarf is ripped to shreds. It will no longer be compacted by the great weight of matter above it, because that is being stripped away by the black hole; so what happens to it?

    I too wonder about this. As I understand it, & I could be mistaken here of course, the “degenerate matter” making up a white dwarf can exist only because it is compressed immensely by the force of the white dwarfs gravity so once released from the star’s gravitational pressure I’d imagine the material would “depressurise” & explode.

    Given that a white dwarf is a dead star with around the mass of our Sun crushed into a sphere about size of the Earth (depending on exact mass – do we know? Maximum mass of 1.4 solar a.k.a. the Chandrasekar Limit.) then I’m also surprised it takes that long for the black hole to devour its stellar victim.

    @ 21 21. Dr Cy Coe in NL Says:

    (can edit, but can’t delete my own post?) Yup, that’s right.

  26. Sure sign that I’m a parent. I read “devours” and “messy eater” and my first thought was Cookie Monster from Sesame Street.

    Black Hole Monster: “STAAAAAAAAR! om nom nom nom nom nom nom nom”

  27. Gary Ansorge

    26. StevoR

    “I’d imagine the material would “depressurise” & explode.”

    Just think of what must then occur to the white dwarf, as its mass drops below the level required to maintain that degenerate matter state.

    Poof! (ok, a really BIG poof)

    GAry 7

  28. DrFlimmer

    Hm. Would a star really explode, when it loses its degeneracy? Why?
    Degeneracy is just another state of matter, as is liquid or solid.
    I think the gas would just change its state from “degenerated” to “gaseous”, and be done with it. Why should the star explode?

    The degeneracy prevented an implosion, not an explosion. So, when the WD loses enough mass, it should become a gaseous thing again that balances gravity with the gas pressure, but it should not explode.

    Given that a white dwarf is a dead star with around the mass of our Sun crushed into a sphere about size of the Earth [..] then I’m also surprised it takes that long for the black hole to devour its stellar victim.

    One should not forget that the WD has a strong gravity itself. I guess the black hole must pull rather strong on the WD to get anything at all. The matter is bound rather strongly to the WD and is not some loosely gas.

    The Lagrange point between the BH and the companion are quite important here. Only matter of the companion that is “over” the Lagrange point can be sucked in at all, otherwise the gravity of the companion still pulls stronger on the particle than the BH.
    Also the BH must form an accretion disk in order to pull down the matter. The material must lose its angular momentum, a process that needs some time and is not done in a few moments.
    These are just two examples why the BH has to do some hard work to swallow the WD, and why it also takes some time.

  29. Brian Too

    @22. Wayne Robinson,

    Well, my understanding may be wrong, but I was under the impression that while the overall field strengths of a 10 solar mass star and black hole are the same, the field intensities would be very different. The gravitational field of the BH originates with the singularity, while in the original star the field originates with the star matter, which is spread out over a very substantial 3-D volume. And since gravity obeys the inverse square law it drops off rapidly with distance from the source (maybe this isn’t relevant here–not sure).

    23. Grimbold,

    I don’t think that’s the right way of thinking about this. The White Dwarf’s gravity is being overcome by an even stronger gravitational source, which is of course the BH. Yeah, the WD is probably getting ripped to shreds but it’s only because an even bigger dog is taking over. Therefore the opportunity to decompress is not going to arise–the superior gravity of the BH simply takes over and incorporates the WD into itself.

    The way to think of this is as an additive process, with the larger object entirely in control of the addition. I’m supposed to say a merger, but as a practical matter, when a 1,000 mass BH swallows a WD, the BH isn’t affected that much. The WD on the other hand exits normal space and leaves only it’s gravity, spin and charge behind as a metaphoric echo of it’s existence.

  30. Gary Ansorge

    29. DrFlimmer

    “Given that a white dwarf is a dead star with around the mass of our Sun crushed into a sphere about size of the Earth”

    This refers to the point I was attempting to make. If the WD is orbiting close enough to the BHs event horizon for the BH to rip pure neutronium from its surface the other side of the WD is 11,000 km away from the event horizon, with its consequent decrease in Gravity tides. Thus, as the WDs mass reduces on the event horizon side, the opposite side of the WD should(logically) revert to normal matter, with electrons ejected from the neutrons, protons left behind, and the whole WD should begin outgassing,,,but that’s assuming that ONLY the WDs gravity has been the force holding everything “down”. Like a hugh spring with the weight compressing it removed, the WD should rebound(on the side away from the event horizon). Unfortunately, we have no idea how neutronium really behaves in the absence of its G field. It may well be that once neutronium is formed, it would be a stable super nucleon bound by its strong nuclear force.

    GAry 7

  31. DrFlimmer

    31. Gary Ansorge

    Don’t confuse white dwarfs with neutron stars ;) . A white dwarf is made up of “normal” atoms — or maybe I should say “normal” ions. The WD is stable due to the degeneracy of the electron gas. A NS is stabilized by the degeneracy of neutrons and sometimes the matter of the neutron star is called neutronium.

    This doesn’t change your argument a lot, I just wanted to make this clear.

    Tidal forces are, indeed, very important here. Sooner or later the WD will become “spaghettified” (such a nice word ;) ). But for this to happen the WD must be rather close to the BH (although not as close as if it would be a NS). So, we still face the problem of angular momentum, which is, as I think, the most important factor why it takes “so long” for the BH to swallow the WD.

  32. ritchie

    Is this what I saw last night around 3am above Liverpool , UK ? It was a large bright flickering star that seemed to be giving off a firework display,, shooting colors from it in all directions? I thought I was seeing things, so I got my wife to have a look and she said she could see the things emitting from it before I even mentioned it.. This was seen with the naked eye and was strange but beautiful but Its left me wondering what it was !!!

  33. Gary Ansorge

    32. DrFlimmer

    I stand corrected. Tanks.

    Still, I would love to see a neutron star in close orbit of a BH. We stand to learn a great deal about degenerate states. IF neutronium could remain degenerate in the absence of that high G field, there might be a bit of it floating around the galaxy. What a great construction material that could be.

    Gary 7

  34. Dan

    My educated opinion as a Taxi Driver is that Black Holes are not terribly different then White Holes.

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