More cool astronomy news: astronomers have found the most massive stellar black hole so far, weighing in at about 24 – 33 times the mass of the Sun.
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| Drawing of IC 10 X-1 by artist (and my friend and ex-coworker!) Aurore Simonnet. Courtesy of NASA. |
Stellar mass black holes are called that because they are in the same mass range as stars (supermassive black holes are millions or billions of times the Sun’s mass and reside in galactic cores; intermediate mass BHs have hundreds of solar masses and are generally seen in star clusters, where "food" for the black hole is plentiful and they can grow easily). Stellar mass black holes form when a massive star explodes. The outer layers blow off, but the core collapses inward. If the mass of the core is high enough, it forms a black hole.
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| Picture of IC 10. Courtesy of NASA, Adam Block/NOAO/AURA/NSF |
The black hole just found is in another galaxy, a nearby dwarf galaxy named IC 10 (the black hole itself is called IC 10 X-1). It’s a little less than 2 million light years from us, putting it substantially closer than even the Andromeda Galaxy. If a black hole has a companion star orbiting it, then it can siphon off and gobble down matter form that star. As the matter falls in to the hole, it heats up… a lot. It can get to millions of degrees, and give off X-rays.
That’s how this one was found; the Chandra X-ray Observatory spotted its emission. The observations also indicated that the X-rays dipped in brightness with a regular period, which is almost certainly due to our view of the black hole being blocked by the companion star as it orbits the hole. We’re seeing black hole eclipses!
More than just being a curiosity, this gives us critical info on the hole: by observing the orbiting stars, the orbits and therefore the masses can be calculated (by using Kepler’s Laws, first formulated in the early 1600s!). When this was done (using Swift), astronomers were surprised to find the black hole was at least 24 solar masses. As far as we know, black holes in our own Galaxy are formed with much lower mass than that, and it doesn’t look like this one could have eaten enough of the other star to get this big. It really looks like it was this massive to start with.
This means that something odd is going on. A likely explanation is that the star that formed the black hole originally had fewer heavy elements (heavier than helium, that is, like carbon and manganese) than usual, so it would have had a weak solar wind. During its life, a star can lose a lot of mass through its solar wind. If this star didn’t have a strong wind, then it could have retained a lot of its original mass, forming a more massive black hole.
More observations of the black hole are planned to narrow down the mass (the observations have only been able to get a lower limit on the mass; it might be bigger). This also makes it possible that such portly black holes exist in our Galaxy too, though none has ever been found. We think that there are millions of black holes in the Milky Way, but since most of them are loners, we don’t see them; they only announce their presence when they’re eating material. There could be lots of black holes like IC 10 X-1 closer by, but we just don’t see them. Don’t worry– there’s none close enough to hurt us. I mean close in an astronomy sense, like a quadrillion kilometers or so. 
Finding oddballs, objects at extremes, pushes our ideas hard, letting us know where they are strong and where they are weak. So finding objects like IC 10 X-1 is more than just an announcement of a record breaker, it’s actually yet another tool in our workshed helping us understand the Universe.
October 30th, 2007 at 1:10 pm
Why can’t this black hole just be “kinda old” and have gobbled up enough mass to reach 24 solar masses?
October 30th, 2007 at 1:17 pm
Know that’s preaching to the faithful, but… the awe of it…. so far from us that light itself takes 2 million years for reaching us, there is the surreal corpse of a gigantic star… a rupture of space-time surrounded by a gravity well so deep not even light can escape from it. And orbiting along with it, there is a living star which is slowly but mercylessly being sucked out of existence by its undead neighbor… and we, sitting here and looking at the energy pouring from such astronomic act of destruction (which could kill us if we just dared to get as close as to see it in visible light), we humble hairless monkeys in a spinning body of molten iron and silica, can determine the mass of the undead star and its victim’s by using 400 years old mathematics…
Ain’t it like, WOOOW?
October 30th, 2007 at 1:24 pm
Bill Bones is right on. Wow.
Aurore Simonnet’s painting is terrific. This detail really grabs:
http://www.nasa.gov/images/content/195154main_WRstarBH2.jpg
October 30th, 2007 at 1:39 pm
Two million light years hey? …Well for all we know this star most likely does not exist anymore. What we see now is what was happening to that star 2 million years ago. That black hole has had 2 million years to do it’s thing.
Just think for a second if we had the power to get closer to that….that black hole is most likely much MUCH bigger than what we think it is.
October 30th, 2007 at 2:02 pm
This is perhaps an uneducated question, but in theory can a black hole ever get “full”? Or do they just keep gobbling up everything around them?
October 30th, 2007 at 2:04 pm
The first image is now on my desktop.
October 30th, 2007 at 2:59 pm
Why are here some guys always yelling you wouldn’t post about astronomy? This is the second very intersting astronomical story I read here today.
@Cello Man:
They will radiate away fast enaugh because the can do any harm (yes, Black Holes can radiate. This is called Hawking Radiation, named after Stephen Hawking who predicted this radiation which has not been observed so far.)
As far as I know/think, Black Holes could become as heavy as they want to. Everytime they eat some matter they become heavier AND their event horizon (the border of the Black Hole; passing this border there is no escape even for light, in fact, this is the definition of the event horizon, the distance from the center where even light cannot escape) grows. There is no upper limit to the growth. Phil mentioned those Super Massive Black Holes sitting in the centers of Galaxies and weighing over a billion times the mass of the sun. This is incredibly hugh!
On the other hand, some scientist think that there are very small Black Holes weighing only as much as a proton and they think those mini-BMs could be made with the LHC which comes operational next year. But: Don’t worry! They won’t consume the earth
October 30th, 2007 at 3:20 pm
Paul,
From an article on physorg.com:
The IC 10 X-1 black hole has gained mass since its birth by gobbling up gas from its companion star, but the rate is so slow that the black hole would have gained no more than 1 or 2 solar masses. “This black hole was born fat; it didn’t grow fat,” says astrophysicist Richard Mushotzky of NASA Goddard Space Flight Center in Greenbelt, Md., who is not a member of the discovery team.
October 30th, 2007 at 3:27 pm
“…there is a living star which is slowly but mercylessly being sucked out of existence by its undead neighbor…”
Would this have been happening to the star even before its companion became a black hole? Because the star that eventually became the black hole would have had just as much mass, even more, considering the mass that it lost whenever it went supernova.
October 30th, 2007 at 3:41 pm
>> Would this have been happening to the star even before its companion became a black hole? Because the star that eventually became the black hole would have had just as much mass, even more, considering the mass that it lost whenever it went supernova.
Depends. It could be that it’s a relatively recent gravitational capture.
October 30th, 2007 at 4:24 pm
Not necessarily. There is the issue that the supernova explosion may give the remaining compact object a kick (this is known to happen for neutron stars, not sure about whether black holes would also receive such a kick, though the fact that the system is bound after such significant mass loss suggests so), so the orbital parameters currently observed may be significantly different to the pre-supernova orbit.
October 30th, 2007 at 11:14 pm
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December 6th, 2007 at 5:04 pm
2million years.. more like about 5…
In the middle of our galaxy there are two massive black holes..
that’ll be fun children.
December 6th, 2007 at 5:05 pm
2million years.. more like about 5…
In the middle of our galaxy there are two massive black holes..
we will reach the center in 2012…
..
that’ll be fun.