UMass Magazine Online

Winter 2005

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Supergalactic X-Ray Vision
The Chandra Observatory reveals the riddle of hot gas

–Charles Creekmore




	X-ray photos of the colossal cloud complex known as Abell 2125 are giving professor Daniel Wang a first-ever glimpse of the inner life of galaxies. (photo by Ben Barnhart)

UMASS AMHERST ASTRONOMER DANIEL WANG is currently studying a celestial wonder never before beheld by humans. In exquisitely detailed images from NASA’s Chandra X-ray Observatory he is probing the inner workings of a colossal cloud complex formed three billion years ago by the merging of multimillion-degree gases. The phenomenon is literally a distant memory.

The cloud complex known as Abell 2125—which swaddles hundreds of galaxies—also gives us a snapshot of how the universe is constructed.

“Galaxies, you see, are always forming out into even larger structures, or clouds, and those are merging into even more gigantic structures, or complexes,” says Wang. “This is actually the well-defined hierarchical makeup of the universe.”

The universe, then, is configured something like a set of Russian nesting dolls: a riddle, wrapped inside an enigma, hidden inside a cloud. Or, at least it was hidden, before NASA launched its Chandra Observatory, with ten times the resolution of earlier x-ray telescopes. Now Chandra can x-ray the universe in much the same way that your local clinic x-rays your body. In effect, Chandra can depict the skeletal features inside these titanic cloud complexes, an intergalactic anatomy that before was invisible to earthbound telescopes.

“With Chandra we can see many more inner details and textures of cloud clusters than were ever possible before,” notes Wang.

Primeval cloud complexes evolve in a life-and-death struggle that Chandra photographs with chilling accuracy. For example, one image shows the violent plume of fiery gases left by a dying galaxy as it glides through the heavens at 2,000 kilometers per second, creating a space wind that strips the galaxy of its gases, the fuel for forming stars such as our sun. While the sizzling gases, chemically enriched from supernovas and starbursts, are “rampaciously”(as Wang describes it) skinned from the galaxy, it methodically runs out of gas, thus polluting these larger cloud formations.

“Hot gas is important because it is the main body of the universe,” says Wang. “In fact, there is more mass in these gases than all the mass of all the galaxies.”

This is the way a galaxy ends, not with a bang, but with a jet stream. And, as it does, Abell 2125 is nourished. This astronomical event, which we can view now, though it actually happened a quarter of the way back in time toward the original Big Bang, is a case of total recall that Chandra is remembering, quite accurately, at the speed of light.
http://www-astro.phast.umass.edu/

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