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Newfound Gas Cloud Points to Possible Planets Near the Milky Way’s Black Hole


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An x-ray image of the region around Sgr A*. Credit: NASA/CXC/MIT/F.K.Baganoff et al.

Times are tough on planet Earth right now, but at least we don’t have a supermassive black hole lurking just over the horizon.

A new study suggests that stars near the Milky Way’s central black hole may well form planets. The researchers based their analysis on a very recent discovery of a gas cloud making its way toward the galactic center.

On December 14 an international team of astronomers led by Stefan Gillessen of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, announced that they had spotted something heading toward a close encounter with the central black hole, known as Sagittarius A* (Sgr A*), which has as much mass as four million suns. Gillessen and his colleagues interpreted the object to be a dusty gas cloud about three times as massive as Earth, possibly belched out as stellar winds (plasma streaming outward from stars) from the young stars that orbit the black hole.

A few days later, Ruth Murray-Clay and Abraham Loeb of the Harvard–Smithsonian Center for Astrophysics suggested that the newfound object may be much more closely connected to those stars. In a preprint posted to the Web site arXiv.org on December 20, Murray-Clay and Loeb say that the cloud Gillessen and his colleagues discovered could be the disrupted remnants of a planet-forming disk surrounding a star that used to orbit Sagittarius A* at a safe distance but is now plunging toward the black hole. A protoplanetary disk is the swirling pancake of gas and dust surrounding a young star, which can coalesce into planets, asteroids and comets. “This cloud of gas naturally originates from a proto-planetary disk surrounding a low-mass star, which was scattered a century ago from the observed ring of young stars orbiting Sgr A*,” they write.

The star itself would be too faint to see. But as Sagittarius A* has distorted and fried the disk with the black hole’s gravitational pull and the radiation of its environs, it has generated a debris stream around the star that telescopes can detect.

If the young stars orbiting Sagittarius A* host protoplanetary disks, that “implies that planets form in the Galactic centre,” the researchers write. But you wouldn’t want to live on one of those worlds. The galactic center is awash in intense radiation emitted by material swirling around the outside of the black hole, which gets compressed and heated as it falls inward. (It is that radiation from outside the event horizon that allows astronomers to “see” a black hole, which itself holds tight to all matter and photons and hence emits no light.)

Plus there’s always the chance that your host star will get knocked onto an orbit heading right for the black hole, as Murray-Clay and Loeb suspect has happened here. In some cases, the researchers suggest, planets might be torn apart by the black hole’s gravitational pull and produce bright flares as the pieces fall in.

We should soon find out whose explanation for the gas cloud is correct. The cloud, whatever its origin, is on track to swing past Sagittarius A* in mid-2013. If it’s a simple gas cloud, it will get torn apart and partly consumed by the black hole, temporarily brightening the radiation from around Sagittarius A*. If the cloud instead comprises debris from a protoplanetary disk, the star itself should cruise past Sagittarius A* largely unscathed. But the cloud will grow denser as more and more mass from the disk is dragged away from the star. Either way, it ought to be quite a show.

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. N a g n o s t i c 3:18 pm 12/26/2011

    Times are tough on planet Earth? Really?

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  2. 2. JamesDavis 9:15 am 12/27/2011

    Yes. “Times are tough on planet Earth right now” – for scientific explanations. Especially tough when our scientists resort to mimicking other scientists. I think black holes are not what everyone thinks they are. Why can’t they be black stars, and when the black light hits a planet just right, it causes the planet to disappear. The huge black hole (star) at the center of our galaxy could be where all the rest of us ‘stuff’ came from and we see our planet because our eyes can see our yellow star and its planets better than we can see all the black stars and their planets. But if you always look at stars with a closed mind or just mimic the ideas of someone else, black holes will remain black holes and never what they really are.

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  3. 3. tribalgem 5:05 am 12/28/2011

    Hmm – interesting comment on not believing current black hole theories – however, for your consideration are you aware that the main problem for black holes not being formed as per current theory, is that general relativity must fail as a theory of gravity…
    Wiki has a great article on black holes and some new theories suggested by quantum mechanics etc…would love to see you explain your idea more thoroughly than the very briefest of comments which you made. Cheers.

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  4. 4. JamesDavis 12:51 pm 12/28/2011

    “tribalgem”; you can’t raise waves in the science community when all the scientists are flowing down stream in a single line.

    It just seems strange to me that there are planets orbiting that black hold. A black hole that is believed to swallow up everything that comes near it. You would think that a black hole that large would drawn in and swallow half of the Universe and there wouldn’t be any gas clouds hanging around it or planets circling it. If that black hole can capture light and swallow it, I don’t think it would take that hole a billion years to capture a planet and swallow it. The light that is circling that black hole could be light from other stars bounding off its atmosphere and that is what allows us to see it. Scientists were wrong about the Sun orbiting Earth and I think they are wrong about black holes too…they are showing signs of being stars and not holes.

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  5. 5. Wayne Williamson 6:15 pm 12/29/2011

    I seriously doubt you can resolve anything 30k light years away that has three times the Earths mass…sounds like pure speculation…

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  6. 6. scottryan1 4:12 am 12/30/2011

    HOW BLACK HOLES FORM

    black holes only form where mass is.

    every galaxy has a black hole in the centre of the massive mass / centre. do black holes form from massive mass?

    seen as i have know idea about black holes. are there any black holes away from stars / mass?

    if there is, do they go away after a small time.

    it seams that the force of mass, or a massive force makes black holes appear / come.

    I do remember a long time ago someone said a massive star blowing up, formed a black hole, but it went away shortly after that.

    mass is also force. i could see how that would be right. if a star did blow up with that much force = mass, let alone mass near by, it would form a black hole, but if the massive force goes away, the black hole will to. this is why most black holes are in the centre of galaxy’s.

    well the black holes in the centre will stay for a very long time to the others in the milky way. there can not be any or many near the edge of a galaxy. but if there are any just out of the centre, they will be smaller and the more away from the centre, the smaller they will be. as long as they have finished eating.

    Without mass, black holes would not be.

    the force on the centre black hole would be massive, not just from all the mass, but all the stars spinning around the black holes would make mass. mass & force / gravity are the same thing.

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  7. 7. hybrid 2:05 am 01/30/2012

    The Universe is a disturbed field of pure energy seeking equilibrium. Black Holes are the disturbance, according to “The Dynamic Ether”

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