Friday, April 13, 2012

Black Hole's 20,000,000 MPH Wind

Earlier this year, astronomers working with NASA's Chandra X-Ray Observatory reported an interesting phenomenon around the black hole IGR J17091 -- a 20 million mph wind.

Contrary to popular belief, black holes don't indiscriminately suck in every last ray of light. Around larger, so-called super-massive black holes, such as those at the centers of active galactic nuclei, magnetic fields in the accretion disks can excite and heat up in-falling matter in such a way that it creates jets that shoot forth from the poles, as seen in the image of the elliptical galaxy M87, below. Smaller black holes have also been shown to occasionally emit these relativistic jets.

Credit: NASA/Hubble Team

The amount of matter within the black hole's wind was unexpected, though. As Ashley King, lead report author from the University of Michigan, put it, "... up to 95% of the matter in the disk around IGR 17091 is expelled by the wind." That means that it's losing far more matter than it's consuming.

Not only is the wind loaded with matter, the 20 million mph speed is generally only seen around the much larger super-massive black holes, which surprised many scientists studying this system.

One of the other surprises of IGR 17091 is that the stellar wind and jets seem to alternate. In other words, sometimes the black hole is shooting off jets of charged particles from its poles, while at other times, the system is ejecting matter in several different directions. This has led some scientists to believe that the creation of the wind has some negating effect on the jets, but more research is needed to understand the mechanics.

Credit: NASA/CXC/M.Weiss
Located nearly 28,000 light years away, toward the center of the Milky Way, IGR 17091 is a stellar-mass black hole, meaning the star that it formed from was probably between five and ten times more massive than our own Sun. As shown in the artist's depiction above, this particular black hole is part of a binary system, where it "feeds" from its neighbor, a relatively light-weight star about the mass of our Sun.

This may not be "breaking" news, but I just found out about it and thought I would share the information.