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Simulation Explains Supermassive Black Holes
Spy der Mann writes "Using a new computer model of galaxy formation, researchers from Carnegie Mellon University have shown that growing black holes release a blast of energy that fundamentally regulates galaxy evolution and black hole growth itself. According to its creators, 'the model explains for the first time observed phenomena and promises to deliver deeper insights into our understanding of galaxy formation and the role of black holes throughout cosmic history'. Hi res pictures and animations (divX) are also available."
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Have you metaroderated recently?
There are limits to quasar ages based on demographic arguments (the relic holes we see today compared to historical quasar activity and assumptions about the efficiency of the matter to energy conversion). The upper limit is on order of 100 million years or so. I know the timescale for "blowing out" gas/dust on Galactic scales from a powerful quasar is much shorter than that, more like 100,000 years, so I'm going to have to see the jounral article and see what they're saying in this paper. Big difference between those two numbers. Keep in mind that even 100 million years is relatively short compared to a unverse age of 13.7 billion years and may be the "short" timescale discussed.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Here are tons of the most recent research papers on black holes. Definitely an good read for anyone with an interest in physics.
Creative Demolition
Astronomy does pretty well with women, at least compared to other hard sciences. At the undergraduate level, it looks to be close to 50/50. Last year I think we had more female applicants for our summer REU program than males. We're going to admit more women than men into our graduate program this year, too. At the more senior levels, there are fewer women, but the numbers more or less match the historical demographics. My PhD advisor was female, and I have lots of female collaborators and a female grad student. Di Matteo isn't too old -- my generation, 30s. Physics, on the other hand, is still having its problems...
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
No, the black holes CAN'T splatter into pieces. They're too massive, their gravity too strong. All the "crap" around them -- gas, dust -- that is the fuel of the quasar -- that stuff surely does spew all over. The basic accretion process, when things settle down and merg, is for that material to form a flattened disk. When you see a quasar, it is the intense radiation from this hot disk that does all the shining. The black hole just provides the gravity. There may also be relativistic jets shooting out the spin axis, but their formation is not well understood. Neither are the less collimated outflows from around quasars (one of the reasons I'm suspicious about their results -- they're dealing with a broad brush and could be right on that level but we surely don't understand a lot of the details even on an empirical, observational level).
I've got some lecture slides on active galaxies (powerpoint) up at my astronomy website. Look at: This link. There are some some real images, and some artists renditions, you might like. I've just used the powerpoint web format, so it looks crappy in anything but explorer. Sorry.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Just in case, I made a BT link for the video and have it running in the background. So if the site does get SlashDotted, you know where to get it. :)
http://s2.isohunt.com/release.php?id=10330
I'm a signature virus. Please copy me to your signature so I can replicate.
There are interesting pictures on Google Images when you search for big black holes. Science is fascinating.
The high supernova rate resulting from the burst of star formation is likely more of a problem than a central quasar, especially since the star formation can take place outside of the Galactic center. I give my intro astronomy students a problem to computer what the Galactic core would look like if it was a quasar and there was no intervening gas/dust (a really big if, since there is a lot of obscuration now).
Quasars can be 1000 times more luminous than an entire galaxy. The absolute magnitude of such a luminous quasar would be about M = -28.5. If the black hole in the center of our galaxy became a quasar, and obscuring gas and dust did not dim it, what would the apparent magnitude of the galactic core be? Think about the answer and what that would look like in the sky.
The answer is a magnitude of -13.9, about the same as the full moon. It would be more concentrated that the light of the moon, and you'd be able to see it in the day time. But, as I said, intervening gas/dust would diminish it's light, and the Milky Way and Andromeda do not have black holes massive enough to shine as brightly as my example. Our atmosphere would also be there to protect us from X-rays and UV, much as it does now.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
The blackholes don't actually emit anything. The accretion disk is what does the emitting.
Actually, black holes do emit. It's called Hawking radiation. But you're right in that what we see is coming from the accretion disk.
The origin of the X-rays are not well understood, but are thought primarily to come from upscattering of thermal photons in a very hot atmosphere above the accretion disk. All the light basically comes from the stuff right around the black holes moving at relativistic speeds, not the black holes themselves.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Eventually the accreation disk (that does the radiating) will all get sucked in, and then there will be no more "wind", so more matter can be pulled in.
I am trolling
A collision between galaxies is not exactly as dramatic as you seem to think it would be. Remember, stars are light-years apart. Actual collisions between stars would be very rare, and unless the black holes come within an incredibly tiny distance they would just slingshot around each other in a hyperbolic orbit and keep going. The real issue is that large numbers of stars would be flung off into space in the process, but I'd say that if there are any humans still alive then, a boring night sky is something they can live with.
Karma: Segmentation fault (tried to dereference a null post)
If I'm not mistaken, the Milky way and the Andromeda galaxy will collide
You are correct. And a simulation of that can be found here in mpeg format.
The following website gives the hard numbers for whether the women at senior levels matches the historical demographics. It gives the percentage of women who receive PhDs compared to faculty positions for 1992, 1999 and 2003 at many different universities. Grad students in 1992 should have become either full professors or assistant/associate professors by 2003 (depending on when they received their PhDs). Check out the percentage of women who got PhDs in 1992 and compare it with the percentage of women faculty in 2003 for the different universities. With the exception of a few, most universities have a sharp difference between the fraction of 1992 female grad students and 2003 female faculty (assistant, associate and full profs). The number of women faculty does not match the historical demographics. Here are some interesting stats for well-known institutions:
h tml
Caltech:
22.6% 1992 female grad students
13.8% 2003 female faculty (associate, assistant and full profs)
MIT:
20.8% 1992 female grad students
11.5% 2003 female faculty
Harvard:
18.2% 1992 female grad students
6.3% 2003 female faculty
Princeton:
26.3% 1992 female grad students
10% 2003 female faculty
UC Berkeley:
22.6% 1992 female grad students
10.7% 2003 female faculty
Women in astronomy stats (from the American Astronomical Society):
http://www.grammai.org/astrowomen/stats/combined.
Seems astronomy is still having problems too!