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Giant "Blob" Is Largest Thing in Universe

Kate Ravilious
for National Geographic News
July 31, 2006
 
Japanese astronomers have discovered what they call the largest object in the universe: a colossal structure 200 million light-years wide that resembles a swarm of giant green jellyfish.

Using the Subaru and Keck telescopes on the Mauna Kea volcano in Hawaii, the research team found an enormous object containing clusters of galaxies surrounded by gas clouds known as Lyman alpha blobs.

Because the object is so far away, the astronomers are actually looking at something from 12 billion years ago, a mere 2 billion years after the universe is believed to have been formed in the big bang.

This young galactic blob could reveal how and when the earliest galaxies formed. (See a photo of the oldest known galaxy cluster [February 17, 2005].)

Galactic Birthplace

Ryosuke Yamauchi from Tohoku University in Sendai, Japan, and his colleagues used the Subaru Telescope to study a region of the universe known to contain large concentrations of gas.

By placing a special filter on the telescope, they were able to concentrate on the narrow range of light wavelengths expected from galaxies at extreme distances.

With these special "goggles" Yamauchi and his team were able to pick out the giant blob. It spreads out along three wavy tentacles.

Each arm is packed with galaxies around four times closer to each other than the universe's average.

Previously known structures with such high density are much smaller, only about 50 million light-years across.

"The densest regions in the universe are the places where galaxies are thought to have formed first. Because this is one of the biggest structures known, it must be one of the very first to have formed," said Philip Best, an astronomer at the Institute for Astronomy at the University of Edinburgh in the U.K.

(Get some space wallpaper).

Early Origins

Astronomers had predicted that such a structure would exist. Computer models had suggested that some of the most massive galaxies in our universe originated from a blob like this.

"We knew these kind of structures would be out there, but something of this size is relatively rare, and it is really nice to hear that one has been found," Best said.

Some of the gas bubbles in the blob are as much as 400,000 light-years across—nearly twice the size of our own galaxy, the Milky Way.

The astronomers think that these blobs may have collapsed under their own gravity and given birth to "supergalaxies"—the most massive galaxies that exist in the universe today.

"These structures are exciting precisely because they give us clues as to what our own part of the universe may have looked like billions of years ago," said Marek Kukula, also from the Institute for Astronomy at the University of Edinburgh.

"It should help us to piece together the story of how our own galaxy—and, ultimately, ourselves—came to be."

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