Mystery Object Found Orbiting Brown Dwarf


Big planet or companion brown dwarf? Using the Hubble Space Telescope and the Gemini Observatory, astronomers have discovered an unusual object orbiting a brown dwarf, and its discovery could fuel additional debate about what exactly constitutes a planet. The object circles a nearby brown dwarf in the Taurus star-forming region with an orbit approximately 3.6 billion kilometers (2.25 billion miles) out, about the same as Saturn from our sun. The astronomers say it is the right size for a planet, but they believe the object formed in less than 1 million years — the approximate age of the brown dwarf — and much faster than the predicted time it takes to build planets according to conventional theories.

Kamen Todorov of Penn State University and his team conducted a survey of 32 young brown dwarfs in the Taurus region.

The object orbits the brown dwarf 2M J044144 and is about 5-10 times the mass of Jupiter. Brown dwarfs are objects that typically are tens of times the mass of Jupiter and are too small to sustain nuclear fusion to shine as stars do.

Artist's conception of the binary system 2M J044144. Science Credit: NASA, ESA, and K. Todorov and K. Luman (Penn State University) Artwork Credit: Gemini Observatory, courtesy of L. Cook

While there has been a lot of discussion in the context of the Pluto debate over how small an object can be and still be called a planet, this new observation addresses the question at the other end of the size spectrum: How small can an object be and still be a brown dwarf rather than a planet? This new companion is within the range of masses observed for planets around stars, but again, the astronomers aren’t sure if it is a planet or a companion brown dwarf star.

The answer is strongly connected to the mechanism by which the companion most likely formed.

The Hubble new release offers these three possible scenarios for how the object may have formed:

Dust in a circumstellar disk slowly agglomerates to form a rocky planet 10 times larger than Earth, which then accumulates a large gaseous envelope; a lump of gas in the disk quickly collapses to form an object the size of a gas giant planet; or, rather than forming in a disk, a companion forms directly from the collapse of the vast cloud of gas and dust in the same manner as a star (or brown dwarf).

If the last scenario is correct, then this discovery demonstrates that planetary-mass bodies can be made through the same mechanism that builds stars. This is the likely solution because the companion is too young to have formed by the first scenario, which is very slow. The second mechanism occurs rapidly, but the disk around the central brown dwarf probably did not contain enough material to make an object with a mass of 5-10 Jupiter masses.

“The most interesting implication of this result is that it shows that the process that makes binary stars extends all the way down to planetary masses. So it appears that nature is able to make planetary-mass companions through two very different mechanisms,” said team member Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University.

If the mystery companion formed through cloud collapse and fragmentation, as stellar binary systems do, then it is not a planet by definition because planets build up inside disks.

The mass of the companion is estimated by comparing its brightness to the luminosities predicted by theoretical evolutionary models for objects at various masses for an age of 1 million years.

Further supporting evidence comes from the presence of a very nearby binary system that contains a small red star and a brown dwarf. Luhman thinks that all four objects may have formed in the same cloud collapse, making this in actuality a quadruple system.

“The configuration closely resembles quadruple star systems, suggesting that all of its components formed like stars,” he said.

The team’s research is being published in an upcoming issue of The Astrophysical Journal.

The team’s paper: Discovery of a Planetary-Mass Companion to a Brown Dwarf in Taurus

Source: HubbleSite

18 Replies to “Mystery Object Found Orbiting Brown Dwarf”

  1. “The object orbits the brown dwarf 2M J044144 and is about 5-10 times the mass of Jupiter. Brown dwarfs are objects that typically are tens of times the mass of Jupiter and are too small to sustain nuclear fusion to shine as stars do.”

    So both of these objects are brown dwarfs? A small brown dwarf orbiting a big one? 5-10 solar masses definitely isn’t like any planet we know of, but shows that despite the vocabulary we use, there is no defining line between stars, planets, and moons. All are spherical objects formed by gravity. All will orbit around objects of higher mass. The sun and all other stars can be viewed as giant planets with intense gravity, heat, light, and fusion.

    We can even imagine the Earth and all the planets as “moons” of the sun, or Saturn and its moons as a “solar system” in miniature. Even galaxies can be viewed as super-massive solar systems!

    I know that there is a difference in the behavior of each of these, but the patterns that arise from gravity are similar on different scales! Nature is awesome!

  2. @Jlazor, where did you get “5-10 solar masses”? The Sun’s mass is considerably greater than Jupiter’s. 5-10 Jupiter masses, or more, is not unusual if you check the database.

  3. Isn’t that distance more like Sun to Neptune? Saturn is only around 800 million miles from the sun – right? Fascinating article.

  4. Jlazor: A brown dwarf star *must* be large enough to sustain deuterium fusion in its core (about 80 Jupiter masses). If it isn’t large enough to do that, then it isn’t a brown dwarf, no matter where it formed, how it formed, how how long it took to form.

    Whether or not such objects should be classified as gas super-giants (any object too small to fuse deuterium, but large enough to fuse tritium) or whether they should be given a class of their own is up for debate, but they definitely are not brown dwarfs

  5. I have a question for the experts.

    Assume you have a black hole that just barely have the mass that formed the event horizon. But due to hawkings radiation it is losing mass so the event horizon shrinks and the star surface becomes visible.

    Could this exist in reality? And could you call this a brown dwarf?

  6. Any black hole with a mass greater than that of approximately that of Luna (Earth’s moon) will passively absorb enough energy from the Cosmic Microwave Background *alone* that it will keep growing.

    Only a black hole smaller than that would slowly evaporate.

    As to the rest of your question, I have no fraking idea what the answer would be, if that were possible;).

  7. What do you mean with that gopher65?
    The mass of the moon shrunk as a black hole? Is that ever possible?

  8. I’m not one of the experts but I’ll take a stab at it.

    There’s no star surface to be revealed. The mass of the black hole is the black hole — it is matter collapsed to a state beyond even what you find in a neutron star. The event horizon grows and shrinks with the black hole, because the event horizon is its edge; the boundary between normal spacetime and Dragon Country.

    I guess what you’re asking is if a black hole can “bleed” enough mass, via Hawking radiation, so that it’s no longer a black hole.

    One problem is that Hawking radiation is an awfully slow process. For a black hole of one solar mass, the time required to evaporate away is something like 1.4*10^57 times longer than the age of the universe. And that’s assuming it spends all its time wasting away, never eating anything. The problem with that is the cosmic microwave background, which gopher pointed out.

    The other problem is that a black hole doesn’t revert to uncollapsed mass. Strangely enough, as the mass bleeds away, the temperature goes up. When it hits some critical point it either “explodes” or goes “poof”; no one is sure which — if either, because Hawking radiation has yet to be observed and is still entirely theoretical.

    So you won’t find a brown dwarf that used to be a black hole. It can’t revert back into some other form.

  9. So it actually becomes a dot, it is not something spherelike but very tine? I mean quarks have dimensions will these quarks being squashed too?

    I never thought about cosmic radiation feeding a black hole. Something new I learned.

  10. Theoretically yes, it becomes something tiny. But as far as the state of the particles, beats me. This is why we should be rooting for the remote chance of a micro black hole spawning in the LHC rather than fearing it.

  11. Olaf: I doubt that any natural mechanism exists to make small black holes of plant or moon mass, but much smaller black holes (IE, the mass of subatomic particles) might naturally form… and nearly instantly evaporate.

    My point was that no black hole will evaporate if it is more massive than Luna. Since all stellar mass black holes are much, much, much more massive than Luna, they will *always* gain energy from background radiation faster than they can evaporate it away. They’ll gain energy from eating other things too of course, but even if they’re in the dead of space with nothing else reaching them, they’ll *still keep growing*, just due to them sucking up background radiation.

    Thus, the scenario that you propose won’t happen… any time soon, anyway.

    That is the caveat . As the universe expands, the density of background radiation decreases as the Cosmic Microwave Background is stretched across a greater and greater volume of space, so eventually the energy density of the CMB will drop below the point where it will be a viable “fuel source” for large black holes. At that point even the largest black holes will start to evaporate as they starve to death. (MUWHAHAHAHAHAHA!) This will happen long after all the stars are dead and all life has ended, so it’s a moot point from out perspective.

    Back to your original question: what I’ve read suggests that the event horizon never retracts past the matter in the black hole, but rather the black hole loses mass only through evaporation in a fashion that is either random or so close to random that you never see what was beneath the event horizon.

    The event horizon’s volume decreases in direct proportion to the rate of evaporation, so none of the original mass survives: instead the energy contained within that mass is evaporated away by Hawking radiation (I call this the process of being “Hawkinged” to death).

  12. This isn’t my area either (no GR), but let me have a stab at expanding on other comments:

    The mass of the moon shrunk as a black hole?

    AFAIU any mass can become a black hole, _if_ you can compress it into a small enough volume. (Modulo when you run up against the Planck volume.)

    So it actually becomes a dot, it is not something spherelike but very tine?

    Semiclassically you see that black holes have only a few quantum properties (mass, area, charge, angular momentum). And no, no volume property, so nothing “spherelike” is attributable to them despite them having an area. (Or an event horizon a bit away.)

    [The rest of the structural properties is irretrievably lost, and how that happens without breaking some laws like 2nd law of thermodynamics have been one of the mysteries. (Now there are some solutions to this problem to choose from, see Hawking, Weinberg (IIRC) et cetera theories on that.)]

    But when you go to deeper theories like string theory it seems (to me, at least; but no ST either) one of the perspectives you can land in is that black holes are “giant” (complex) quantum states of their own. In such a case there is _intrinsically_ no volume, not even a “dot” property, no more than a charge or an angular momentum is a dot.

  13. Interesting, area and angular momentum but no volume.

    I am going to pretend that I understand it. LOL

    Yes the Moon can be compressed into a black hole, but the Moon then need some external force to collapse it.

  14. Well i was looking around and well i found this really intresteing cause of many ression and cause i have an intreste in space.

    But a little wile ago like a lot of people i guess i was reading about the whole 2012 end of the world thing and well recentley i have been made intrested in it agian not cause of the end of the world thing and i’m not some holy joe either but i just think that it is a little bit funny cause well.

    It would seam that for some unknowing reasion part of space on google sky is missing and by that i’m not talking about a mistake or a error in the progream either some one have black out a part of space and it is clear that someone dose not what some thing to be seen just yet like and well there may be millions of ression why but it dose seam a little bit funny to me and also well after doing a little reading on the whole 2012 thing that the mayan’s have kinda warned that there is an 10th outter solar system planet.

    Now i know that the thought of such a thing been real sounds a little silly that another planet could be just out side of our solar systerm orbeting around our own and of course that fact that we would be able to see it but there in it sell lay one of the most intresting qustion and that is.

    Well if in fact Nibiru is real and it is a brown dwarf star it would olny be really able to see it with the use of infar red till it was about the same distince as our moon and well with all that info if it was real it would be lest that 2 years away from from with would mean we would not see it in the sky yet and well dose it not just seam a little bit funny how nasa has just found what is been called the brown dwarf 2M J044144 and funny that there is some thing like a planet that is orbiting it could this be Nibiru the plante x ?

    As for me self i have not idea wither it is or not just pointing out is it not odd that went you look at the info that you can find easyley on the net how thing’s start to fall in to place.

    Now i’m not saying that it is or that any thing will happen in 2012 at all and well you believe that some thing will happen good for you like if not also good for you like i just think that it is odd do you?

  15. I like the idea of a new catagory between gas giants and brown dwarfs.

    btw, How many Jupiter masses is the sun?

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