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Scientist say 'party atmosphere' gives clue to galaxy creation

Galaxies start off full of energy like a raging house party, but eventually quiet down as they age, according to research.

January 26, 2012|By Joseph Serna

A team of astronomers that includes a leading UC Irvine scientist has found a missing link that shows how the universe's most active star-creating galaxies evolve into its largest and quietest ones billions of years later.

UCI post-doctoral scholar Julie Wardlow and her colleagues accurately measured the invisible halo of dark matter — visible only through its gravitational effects on light and mass — that surrounds the universe's galaxies.

"It's important in terms of galaxy evolution," Wardlow said. "Somehow the galaxies in the past need to transform into the galaxies of today."

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One way to look at it would be viewing the universe as your neighborhood, with a new family building a house, or galaxy, next door.

They relied on the Atacama Pathfinder Experiment telescope in Chile with NASA's Spitzer Space Telescope, among others, to assist in the research.

At the center of every house are "the parents," or black holes. Until this recent discovery, scientists couldn't draw a specific link to how this home with a few "kids," or stars, running around and making noise eventually turned an older, quieter place to live. Now they do.

Consider that one night the parents go to sleep early. The kids tell their friends to come over, and soon you have a party with music and other kids showing up. That is a starburst galaxy. Inside the house, it's full of life and chaos.

"We're observing them in a very, very active phase," Wardlow said of the starbursts.

All the cars that the kids' friends came in? That's the dark matter.

Because that party is so noisy, it definitely doesn't last long — about 100 million years, just a hiccup in the life of a neighborhood about 14 billion years old. When the parents wake up, they suck all the energy out of the party.

Some kids and close friends stay, but most are thrown out, though their cars stay put outside. That's a quasar, or the aftermath of a starburst. The parents shoot radiation — a bunch of high-energy, destructive matter — out into the cosmos to wreak havoc on the rest of the neighborhood, or universe.

What's left is the final stage, the elliptical galaxy. It's huge because the kids have grown up and maybe have families of their own. The house is bigger, but there's no more star creation, no more raging parties. It's quiet.

Using telescopes, scientists saw that all the dark matter, or cars, early on indicated it was a young, cool place to be. As the galaxy aged, the house grew, and so did the amount of cars outside.

The discovery could reveal our own Milky Way galaxy's future, as it's expected to possibly collide with the Andromeda galaxy. According to scientists, it would be one heck of a party.

joseph.serna@latimes.com

Twitter: @JosephSerna

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