Living On The Edge Of Oblivion

January 08, 2009

This week astronomers at the American Astronomical Society (AAS) meeting in Long Beach, California got their most detailed yet look at the sprawling center of our galaxy. You can look in the direction of the galactic core on a summer's night, it's in the constellation Sagittarius. But thick lanes of stars and coal-black dust prevent our direct view of the center.

But super-sharp, dust penetrating near-infrared light images from the Hubble Space Telescope reveal a dramatic fantasy landscape. For starters the core is chock full of stars set against a background tapestry of stalagmite-looking fingers of dust on the edge of giant molecular clouds, the incubators for new stars. Several super massive young star clusters are home to some of the brightest stars in the galaxy.

At the center of action, quite literally, is the massive cluster that sits smack dab on top of the Milky Way's central black hole -- a 3 million solar-mass sleeping giant. What has puzzled astronomer for years is that bright blue young stars can be see very close to the black hole, within a distance of just a few light-years. They are too young to have traveled there. It has always been hard to imagine they could form so close to the black hole.

New observations by the Very Large Array radio telescope near Socorro, New Mexico now have found stars forming near the central black hole.  Within this region, gas molecules are strengthening naturally occurring radio emission in the same way that lasers strengthen light beams. These areas are called cosmic masers, and they accompany new star formation.

Since most gas clouds are light-years across, this means these maser-forming clouds near the central black hole must be smaller and more dense than usual to avoid being tidally ripped apart by the black hole's gravitational tug. In this extreme environment stars, and any accompanying planets, would whip around the black hole at a dizzying rate.

If you were on a planet in this hyperactive zone the sky would be ablaze with many more stars than seen from Earth. There would be a bright concentration of stars off in one direction surrounding the central black hole, which would not be visible from a few light-years away.

Unfortunately, the radiation from super-hot gas swirling into the black hole would probably make it difficult for life as we know it to arise, veteran black hole researcher Andrea Goetz told me at an AAS reception. This is too bad because I was ready to go on and wildly speculate how a civilization might cope with living life in the fast lane is a swirling disk of stars precariously close to a black hole.

What makes the presence of life even more problematic is that the stars are so close together in this region that planetary systems might not stay intact. Planets would be dislodged from their orbits and go sailing off as orphaned worlds. Encounters with other stars might send planets and their stars plummeting into the black hole, or catapult them out of the galaxy as hypervelocity objects.

Other research presented here at the AAS meeting supports the idea that black holes are the seeds around which galaxies form. This addressed a chicken and egg question: what came first, our galaxy's black hole or the first generation stars? Radio telescope observations of primeval galaxies that existed less than one billion year after the big bang show that super massive black holes already dwell at their centers, and suck in huge streamers of gas. The black holes may facilitate the early formation of stars in these streamers. But the black holes may squelch star formation later on by energetically blowing gas out of a galaxy via extragalactic jets. So back holes may regulate a galaxy's growth.   

Talk about the tail wagging the dog! 

Comments

[Adam]

Would be cool if black-holes really did form stable wormhole bridges between galaxies or even universes. Imagine if the Universe was already engineered at, or just after, the Big Bang and given a bunch of wormhole subways between the future galaxies. Perhaps our Universe is but one in a very long series, and Life in previous expanded phases has engineered the topology to nucleate the galaxies and give the new Universe a head-start