New, "Luminous" Galaxies Are a Wild Bunch

Anne Minard
for National Geographic News
August 10, 2007
Astronomers just got new glasses—and they're helping reveal the universe at its wildest.

A new study has found unusually large, prolific galaxies dating back to just two billion years after the universe formed around 13.7 billion years ago.(Explore a virtual solar system.)

Using new telescope technologies, a global team of 25 researchers are chronicling the galaxies' early lives, when they churned out stars a thousand times faster than the Milky Way, astronomers say.

"It's a real surprise to find galaxies that massive and luminous existing so early in the universe," said astronomer and lead study author Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.

Astronomers had believed smaller, dimmer galaxies were much more common in the early universe, because it takes time for galaxies to form and grow. (Related: "Eight New Neighboring Galaxies Found, Scientists Announce" [January 10, 2007].)

The findings were published this week in the Astrophysical Journal.

Sharper Focus

Astronomers believe the galaxies are so violent, with new stars constantly colliding and merging, that they also churn out massive amounts of dust. (Related: "Colossal Four-Galaxy Collision Discovered" [August 7, 2007].)

Grant Wilson, an assistant professor of astronomy at the University of Massachusetts and a co-author on the new paper, said astronomers once underestimated the rate of early star formation in bright, active galaxies because their dust hid the starlight.

But because the new galaxies are so massive and hot, their stars heat the surrounding dust to about -387 degrees Fahrenheit (-233 degrees Celsius)—about twice as warm as dust in the Milky Way.

Those are perfect conditions for astronomy's newest tools—telescopes that are built to capture nonvisible light—to detect the galaxies, experts say.

Old News?

Not all astronomers agree the results are such a surprise.

The new paper is one of several in the past two years that have "discovered" the wild galaxies.

Scott Chapman at the University of Cambridge's Institute of Astronomy in the United Kingdom published his own sightings of such galaxies in 2005.

He said the current paper "really does not offer anything new to the speculation."

George Rieke, at the University of Arizona in Tucson, led NASA's Spitzer Space Telescope team for 15 years. He declined to comment on the paper.

"I think praising the new work would get me in trouble with those who did the older effort," he said.

Nevertheless, the new galaxies further open a stunning new window into the skies, many experts agree. (Learn about galaxy hunters.)

You Can't Believe Your Eyes

Wilson said it took so long to see these galaxies partly because of human bias.

"Our eyes are adapted to optical light and that's how we built our telescopes," he said.

But dust hides most of the starlight in the bright galaxies, and optical telescopes aimed straight toward them—even the Hubble Space Telescope—see only darkness.

The Spitzer Space Telescope can see the galaxies because it uses infrared wavelengths, though it gets interference from other galaxies.

A newer breed of telescope, called submillimeter telescopes, uses wavelengths between the infrared and radio wavelengths.

The James Clerk Maxwell Telescope in Hawaii, which originally spotted the new galaxies, will soon be fitted with a new submillimeter camera.

The device will allow it to detect hundreds to thousands of hot, distant galaxies every year.

And the Large Millimeter Telescope, under construction now in Mexico, will open the door to discovering hundreds of such galaxies per hour, rather than hundreds per decade, Wilson of the University of Massachusetts said.

The galaxies provide countless opportunities to study new stars.

Scientists still don't really know how stars form or how starbursts happen, Wilson said, but now all those processes may come into focus.

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