Hubble lets astronomers glimpse formation of earliest galaxies Infrared examination believed to show stars about 12 billion years ago

October 09, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

WASHINGTON -- Astronomers peering out beyond the most distant known galaxies in the universe have discovered well, more galaxies.

Using a new infrared camera aboard the Hubble Space Telescope, the researchers have found faint red dots and streaks, perhaps 12 billion light-years away, that appear to be part of the first generation of galaxies ever to form.

If they're right, their pictures reveal a portion of the universe as it existed at just 5 percent of its present age. They suggest that stars were assembling themselves into galaxies as early as 700 million years after the Big Bang, which scientists believe was the beginning of all space, matter and time.

"These are the deepest images of individual galaxies ever obtained," said University of Arizona astrophysicist Rodger I. Thompson. The pictures fulfill a key Hubble objective and reveal "places and times in the universe we really had no view of before."

The galaxies' precise distance won't be known until astronomers can get more light from them to analyze. That, Thompson said at NASA headquarters yesterday, will require either techniques not yet invented or advanced telescopes not yet built.

Alan M. Dressler, an expert on the beginnings of the universe who is not connected with the Hubble discovery, called the feat an "exciting first step in our infrared view of the early universe."

"We must be getting very close to seeing the original building of the things we call galaxies today," he said.

Astronomers are able to see deep into space and far back in time because even light -- traveling at 186,000 miles per second -- needs time to get from there to here.

The sunshine in your eyes at rush hour on the Beltway, for example, left the sun about seven minutes earlier. Light from a star one light-year away (5.9 trillion miles) needed a year to get here. We see that star as it existed one year ago.

Likewise, when astronomers get pictures of galaxies 12 billion light-years away, they are seeing those galaxies as they existed 12 billion years ago.

Astronomers curious about how galaxies have evolved since the Big Bang can examine the composition and structure of those visible at various distances -- and so at various points back in time -- and try to understand what has happened over time.

The early galaxies in this latest Hubble discovery were spotted in a portion of the sky called the "Hubble Deep Field." Situated above the spiral plane of our Milky Way galaxy, it was chosen for study because it seemed quite empty.

To the astronomers' delight, the 1995 photographs of the Deep Field -- snapped in visible light by Hubble's Wide Field/Planetary Camera -- revealed a swarm of galaxies in a bewildering variety of colors, shapes and sizes. They were packed into a region of sky that would appear from Earth as wide as a grain of sand held at arm's length.

Those galaxies appeared as they existed 8 billion or 9 billion years ago, when the universe was 10 percent of its present age.

Many of them, however, looked oddly shaped, with strangely distributed lumps of hot, young stars. "Many of us wondered if we were missing something," said Dressler.

They needed to look again in infrared wavelengths.

Why? First, because visible starlight can be absorbed and blocked from view by the swirling dust in many galaxies. Only infrared sensors on orbiting telescopes can see through the dust to reveal the stars within and the galaxies' true dimensions.

vTC Second, as the universe expands, so does the light traveling across it. Visible light waves en route to Earth for eons of time expand like a Slinky into longer wavelengths. Eventually they become infrared radiation invisible to the human eye.

To see such hidden and distant objects, astronomers needed Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), which was installed during NASA astronauts' last service call early in 1997.

On the NICMOS infrared images, astronomers found two things that were new.

Those oddly shaped, lumpy, visible-light galaxies had suddenly been filled in, and they looked like quite normal-shaped, dusty galaxies.

The astronomers also spotted dozens of reddish dots and streaks they hadn't seen in visible-light images. Those matched calculations for how galaxies would appear at much greater distances than those in the 1995 Hubble Deep Field pictures and several billion years closer to the Big Bang.

Delighted as they are, astronomers will have vexing problems if they look still farther back in space and time, and continue to see more and more stars and galaxies, Dressler said.

Cosmologists would have to come up with new theories to explain how such objects could form so quickly after the Big Bang.

Pub Date: 10/09/98

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