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  sci-tech > space > story pagecorner  

Hubble snaps clues about origin of spiral galaxies

spiral galaxy
A picture of a spiral galaxy taken by the Hubble Space Telescope  

October 6, 1999
Web posted at: 4:22 p.m. EDT (2022 GMT)

In this story:

Are all galaxies created equal?

Bulge has puzzled scientists for years


WASHINGTON (CNN) -- The Hubble Space Telescope is giving astronomers new clues about the birth of spiral galaxies like our own.

One team of astronomers studying pictures from Hubble said Wednedsay they had confirmed that the central bulges of the more tightly wound spirals were all created at more or less the same time in the early universe.

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VideoCNN's Miles O'Brien reports on the size and age of galaxies as seen from the Hubble Space Telescope.
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The team, led by Reynier Peletier from the University of Nottingham in the United Kingdom, used the Hubble to look into the center of 20 spiral galaxies that have large bulges.

"What they found that is quite surprising is that all of them are old," Peletier said at a news conference Wednesday. "All of them were formed within a period of only two billion years."

Scientists said the relatively brief incubation period for these galaxies could have happened through the collapse of a single hydrogen cloud or through the merging of primeval star clusters.

"These bulges (in the spiral galaxies) are as old as the oldest galaxies we know of in the universe, which are the ellipticals and clusters," Peletier said.

Peletier said scientists also found newly formed stars in the spiral galaxies.

Are all galaxies created equal?

hubble picture
The anatomy of a spiral galaxy  

A second team of astronomers led by C. Marcella Carollo of Columbia University in New York surveyed galaxies that have smaller bulges with bar-like structures across them. Carollo said Hubble gave scientists new information about the age of galaxies.

"We have seen that the massive bulges are essentially very old systems," Carolla said. "This is teaching us that the formation of these fundamental components of galaxies occurs very early in the universe when the universe is very young."

But Carolla said this is not the whole story. Her team found that at least half of the smaller bulges formed in different ways.

They are not miniature versions of the massive bulges, Carolla said. "But they're actually very complex structures in their centers."

She said the smaller bulges have a lot of young stars and, in the center of the systems, a central dense source. This is believed to be a star cluster.

Bulge has puzzled scientists for years

David Leckrone, a Hubble Space Telescope project scientist, explained that spiral galaxies are mostly flat.

"Our galaxy, and spiral galaxies in general, are basically flattened, pancake-shaped discs," said. "They have within those discs spiral patterns of stars and clouds of gas and dust."

But in the middle of spiral galaxies, there's a clump that has puzzled astronomers for a long time.

"In the center of the galaxy you see both a bright nucleus and surrounding that nucleus a larger, roughly spherical shaped region called the bulge," Leckrone said.

Scientists believe learning how the bulges formed can help them understand how our galaxy formed.

The two teams used the high-powered Hubble Space Telescope's visible light and infrared cameras to look into the bulges of more than 200 neighboring galaxies, some as far as 100 million light years away.

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Hubble Heritage Project
Space Telescope Science Institute
The Next Generation Space Telescope
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