Posted by Davin Flateau on 20 Feb 2006 at 11:13 am.
Filed under General, Astronomy.
University of Arizona astronomer Dr. Fulvio Melia spoke under the giant 60-foot dome of Exploration Place’s CyberDome Theater on February 17 and 18. The assembled audiences were treated to a deep but down to earth explanation of one of the most exotic, cutting-edge topics in science today - the supermassive black holes found at the center of many galaxies. Dr. Melia covered many fascinating developments that have come to light in the short time these objects have been scrutinized. I thought I’d write about just a few of the topics that Dr. Melia covered for the sake of those folks who weren’t able to make it down.
Chicken or the Egg?
Which came first - the galaxy or the supermassive black hole in its center? Originally, it was thought that a galaxy would go through a catastrophic collision with another galaxy to produce a supermassive black hole at its center. However, recent observations suggest a “co-evolution” of the black hole and its surrounding galaxy. This means a big public relations boost for black holes. Often associated with death and destruction, it seems now that black holes may be the key to the creation of galaxies, including our very own. Like any good press agent would say: you can’t buy that kind of positive publicity!
The Milky Way vs. The Andromeda Galaxy
The Ultimate Rumble in the Jungle. I can hear it now:
Aaaand in this corner - weighing in at 200 billion stars, don’t call it a candy bar, it’s our own Millllllky Way Galaxy! And in the far corner - 2.5 million light years away to be exact - weighing in at an astounding 1.5 times that of the Milky Way, she’s big and mean, it’s The Andromeda Galaxy!
Our home galaxy is on a collision course with the huge nearby Andromeda Galaxy. Like two semi-trailers barreling down the highway toward each other, you know the result is going to be interesting. The two beautiful spiral galaxies as we know them today will be twisted like funnel cake as invisible arms of gravity tear at each other to form a new entity 3 billion years from now.
As the new “Andromeda Way” galaxy slowly starts to take the form of a football-shaped elliptical galaxy over the next billion years after the collision, the supermassive black holes from the two original galaxies will combine. The merger of these two massive objects will “ignite” the core of our Andromeda Way, and the newborn galaxy will start to flare massive amounts of energy out in the Universe as the new black hole consumes a tremendous amount of material. Our new galaxy will become a quasar as our new home joins some of the most energetic objects in the Universe. See a movie of a supercomputer simulation of the merger by John Dubinski from the University of Toronto.
Dancing Stars in the Milky Way’s Center
Can we see the black hole at the center of our galaxy? It’s not easy. Black holes are, well, black, and even supermassive black holes are still quite tiny, only about the size of the distance from the sun to the orbit of Mars (about the size of a large star). Throw in 28,000 light years worth of stars, dust and gas obscuring our view, and the task may seem impossible. By looking at invisible wavelengths that pierce all the dust and gas in the way, astronomers have managed to peer into the inner sanctum of the black hole’s lair, and it’s a bizarre place.
In the immediate vicinity of the supermassive black hole in the center of the Milky Way, astronomers have seen the awesome effects of concentrating the mass of 4 million suns into such a tiny space. The black hole is surrounded by hot gas and dust, bursting with huge amounts of x-rays as mass is converted into energy near the black hole. Thousands of stars are crammed into just a few light years, bathing the entire region in crowded starlight.
In the space the size of a solar system, entire stars fly at incredible speeds, whipping around the black hole in highly eccentric orbits, similar the orbits of comets around our sun. The picture you see here is not an animation, but is a movie taken from actual observations over the last decade or so.
The technology doesn’t quite exist yet to image the supermassive black hole itself, but that could change soon. The Very Long Baseline Array, with its hemisphere-wide network of telescopes that combine to act like one huge telescope, should be able to actually take pictures of the “shadow” of the event horizon in the not too distant future. 8×10s and wallet sizes will be extra, though.
