LEXIS-NEXIS® Academic Universe-Document
Copyright 1996 Times Mirror Company  
Los Angeles Times

May 6, 1996, Monday, Home Edition

SECTION: Part A; Page 1; Metro Desk

LENGTH: 1504 words



In a string of discoveries that have opened a door to our distant past, Caltech and UCLA astronomers have caught sight of galaxies like our Milky Way just coming into being, switching on their first stars.

These so-called protogalaxies offer astronomers a glimpse 13 billion years back in time to when sun-like stars were beginning to ignite inside wombs of hydrogen gas.

"It means we can study the natural history of the universe," said astrophysicist Matthew Malkan of UCLA, who published one of the first sightings last summer. "But this is even better than fossils because these are alive, and we're watching them in their natural habitat."

By studying the infant galaxies as they evolve, astronomers hope to extract clues to some of the most fundamental mysteries in physical science--including how galaxies form, how the universe got its overall structure, and how the chemical elements were created. Scientists have been able to see as far as 85% of the way back to the beginning of the universe. As recently as five years ago, astronomers didn't think galaxies existed so early in the history of the universe, said Caltech astrophysicist Charles Steidel, who has found dozens of the infant galaxies. The universe had not cooled sufficiently for matter to congeal into large structures, they believed.

Even if these early galaxies did exist so far back, astronomers thought, they would be too dim to see.

Now new technology--in particular the Keck telescope in Hawaii and the Hubble Space Telescope--has changed all that.

"Before 1995, no protogalaxies were known," said Malkan. "Now they're going to become routine."

Four groups of astronomers have seen glimmers of ancient galaxies since the summer of 1995, each using a different strategy. Still, finding them remains "monstrously difficult," said Malkan. Because the galaxies are so distant and dim, only the sharpest telescopes and most patient astronomers can tease them out.

To qualify as a galaxy, most of the gas in an interstellar cloud needs to be turning into stars.


Since Malkan's group is looking for infant galaxies, it searches for the signature of starlight that only comes from very hot, young, fast-burning stars. Ultraviolet light from the stars pumps energy into hydrogen atoms in the cloud, which then glow. "It's just like a neon tube," Malkan said.

The light comes encoded with a wealth of information, much like a voice print. A series of bright and dark lines spells out a visible imprint of the harmonic tones that atoms sing out when strummed by specific frequencies of light. The astronomer reads these lines like words on a page. The pattern they make gives clear information about the source of the light, its motion, its energy and even its history.

The light carries this information through the expanding universe for 13 billion years or so before it reaches the extinct volcano on Mauna Kea where the Keck sits. The time lag means that these protogalaxies could well have developed into mature galaxies like the Milky Way by the time the light reaches Earth's shores. (If, perchance, astronomers in that mature galaxy 13 billion light years away have recently found the Milky Way in their telescopes, they would see only an infant galaxy in the first stages of creation.)

Not only are the astronomers looking back in time, they are seeing the origin of chemistry. Because all atoms except hydrogen and helium are cooked up in stars, watching the first stars light up is a way to watch the original atomic alchemy that produced everything from diamonds to dust. "We used to just have theories about how the elements formed," Malkan said. "Now we can see it happening."

The 13-billion-light-year journey has a noticeable effect on the light: it gets stretched into longer wavelengths, some of which arrive on Mauna Kea as infrared radiation. Malkan's group looks for these stretched light waves in part because long waves bend more easily around interstellar dust (just as long radio waves bend around cars).

But looking at infrared wavelengths also poses enormous problems. Infrared radiation is heat, and even the warm glow of the night sky is enough to drown out the light from a galaxy.

"We're looking for that blip of excess radiation that stands out from the radiation coming from the sky," Malkan said.

Once they locate the blip of radiation, the astronomers take a more detailed look to make sure they are seeing what they think they're seeing. However, to see the patterns of lines etched into the spectrum, the detector attached to the telescope in effect spreads the light as if it were going through a prism, dimming it a hundredfold.

While merely spotting a protogalaxy can be done by a number of powerful telescopes, only the Keck can sort out the spectrum. So far the UCLA group has pinned down one spectrum, and from the looks of it, the protogalaxy is producing stars at the rapid rate of 130 per year. "It's a burst of star birth," Malkan said.

Another recently discovered protogalaxy is even more prodigious, producing perhaps a 1,000 suns a year. But this discovery, said University of Colorado astronomer Erica Ellingson, was completely serendipitous. Her team was measuring the velocities of nearby galaxies with a smaller telescope on Mauna Kea when this one "stuck out like a sore thumb," she said. If the galaxy turns out to be what it appears to be, it will be the brightest galaxy ever observed--about a hundred times brighter than the Milky Way.


Meanwhile, the Hubble Space Telescope picked up multiple images of what scientists think is yet another protogalaxy--this one only about 60% of the way back to the beginning of the universe.

While the object looks like a protogalaxy, it is even more interesting to astronomers for a different reason. It is the clearest sighting yet of a bizarre phenomenon predicted by Einstein known as gravitational lensing. In effect, the immense gravity of a star group sitting between Earth and the galaxy bends light like a lens, greatly magnifying the image--and in this case, producing multiple distorted copies like images in a fun house.

The galaxy, says Princeton's Wesley Colley, one of its discoverers, is probably not the kind that will mature into a Milky Way. "This may be a kind of weirdo," he said. "It's large and it has a funny shape to it."

In contrast, Caltech's group is looking for very normal infant galaxies so they can better understand the early development of our own Milky Way. "We are looking for average things," Steidel said, "rather than looking for bizarre mutations that make themselves easy to be found."

Steidel's approach, said Ellingson, is what all the astronomers should be doing. "It's very systematic, very scientific."

Steidel uses a technique that has picked out hundreds of possible protogalaxies and a few dozen sure ones. In effect, he looks for signs that the ultraviolet light from the hot, young stars has been absorbed by the hydrogen cloud. Only light from hot young stars would be so completely eaten up by the cloud, he says.

In a sense, Steidel is looking for the telltale shadow of the ultraviolet light--or what he calls the "ultraviolet dropout." This is essentially just the opposite of what Malkan is looking for; his door is Malkan's window.


Because his group has found so many protogalaxies, Steidel is confident that they will be able to tease out information about how the universe formed galaxies and clusters of galaxies in the first place.

"The really exciting thing is, we can ask: What are they? How are they clustered? For the first time we have actual observational evidence for how structure develops in the universe."

Meanwhile, Malkan's group found evidence of carbon atoms in the galaxy he looked at. Because carbon can only be created inside stars, and then regurgitated into interstellar space to form other stars, the presence of carbon suggests that these are not first-generation stars, but rather their children.

"The carbon tells you this galaxy has already been making stars," said Malkan. If so, that means protogalaxy hunters may be able to look back even farther to find their ultimate ancestors.

"We haven't pointed to anything that says: We have seen the very first moment of the very first birth of the very first star. That would be awesome. And I think we're going to see it someday."

Baby Pictures

The light from embryonic galaxies travels through the expanding universe for 13 billion years or so before it reaches the Hubble Telescope orbiting Earth. If astronomers in those galaxies found the Milky Way in their telescopes, they would see us the way we were 13 billion years ago, an infant galaxy in the first stages of creation.

In the box above is an image of an infant galaxy taken by Hubble. Over the eons it took the light to reach Earth, a mature galaxy, like that indicated by the arrow, has probably developed.

Sources: NASA, Caltech

GRAPHIC: GRAPHIC-CHART: Baby Pictures, Los Angeles Times

LOAD-DATE: May 6, 1996