Friday, November 24, 2006

RAGTAG SPIRAL

Unlike the massive elliptical galaxy featured in the previous post, this "topsy- turvy" starburst galaxy seen in this image by the European Southern Observatory's Very Large Telescope in Chile is a comparative lone wolf, undergoing an unusually large amount of stellar formation. Starburst galaxies usually result from mergers with other galaxies in galaxy clusters.

At a distance of some 15 million light years in the minor southern constellation of Reticulum, NGC 1313 shows no evidence of such mergers and it has no nearby neighbors.

Not only is it oddly asymmetrical and riddled with starbursts; deeper x-ray imaging reveals that NGC 1313 has at least two black holes, estimated to be hundreds of times the mass of our own sun. Our own Milky Way has a supermassive black hole in its center, and our galaxy is also rife with smaller black holes produced from massive single stars. But NGC 1313's intermediate-mass black holes as identified in images of ultra-luminous x-ray sources (ULX), can't be easily dismissed with current theory. That's mainly because astrophysical theory doesn't readily explain how such intermediate-sized black holes could form from a single binary (or double) star system.

Image: ESO

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