Image: Distant galaxy
ESO
Photos from the European Southern Observatory show the distant galaxy known as Abell 1835 IR1916 within the circles. The right image is an enhancement of the area defined by the box in the left image.
By Senior science writer
updated 3/1/2004 5:40:35 PM ET 2004-03-01T22:40:35

Astronomers say they've peered deeper into the cosmos than ever before, recording light that left a galaxy when the universe was just 3 percent its current age.

The discovery represents an important and challenging leap in time and space beyond the previous recordholder and points to more record-setters to come. The galaxy is 13.23 billion light-years away, seen when the universe was 470 million years old.

Likening the universe to an 80-year-old human, the astronomers said the previous record holder would be a 4-year-old child, while the newfound galaxy is just 2½.

The galaxy is thought to be one of the first to form, in an era when a thick "fog" had begun to lift and end the so-called cosmic Dark Ages that followed on the heels of the theoretical Big Bang. It and others found in the same study will help theorists refine ideas about how galaxies initially developed.

The near-infrared observation was made with the European Southern Observatory's Very Large Telescope in Chile. In a sort of "Best Supporting Actor" role, an intervening cluster of galaxies served as a giant, natural magnifying glass, making is possible to detect the more distant galaxy.

"This discovery opens the way to future explorations of the first stars and galaxies in the early universe," said the study's co-leader, Daniel Schaerer from the Geneva Observatory and University in Switzerland.

Shattering the record
Light from faraway objects is stretched during its travels across space. The wavelengths of visible light are gradually shifted from blue to red, toward invisible infrared light. Scientists measure this stretching with a scale they call redshift.

Prior to Monday's announcement, the most distant galaxy — presented just two weeks ago — was estimated to be somewhere between redshift 6.6 and 7.0 and was said to be 13 billion light-years away. It had supplanted a redshift 6.4 galaxy that was announced in January 2003.

The redshift scale is like a logarithmic one: The difference between redshift 1 and 2 is billions of years, but the difference between redshift 6 and 7 is only hundreds of millions of years. The most distant echoes of the cosmos come from redshift 1,000 or higher, radiation that's stretched into radio waves.

The new No. 1 sits at redshift 10, according to Schaerer and his colleague Roser Pello from the Observatoire Midi-Pyrenees in France.

More record-setters possible
Getting to redshift 10 and beyond, many scientists have thought, would be extremely challenging if not impractical until next-generation space telescopes are built. One scientist involved in finding the redshift 6.4 galaxy in January 2003 said last month that getting routinely beyond redshift 6.5 with current telescopes would be very difficult.

Schaerer is more optimistic.

"Though technically difficult there's no reason why one should not be able to find galaxies beyond redshift 7," he told Space.com.

Here's why: The newfound galaxy is catalogued as Abell 1835 IR1916. The intervening galaxy cluster, whose gravity bends light from objects beyond, magnified the light of the Abell 1835 IR1916 somewhere between 25 and 100 times. There are other, similar natural lenses in space.

Among the challenges astronomers face is sorting out what these magnified observations mean.

After identifying several objects that appeared to be very far away, Schaerer and Pello examined visible-light images from the Canada-France-Hawaii Telescope and the Hubble Space Telescope. The galaxies don't show up in those images, suggested their light had all shifted out of the visible and into the infrared and helping the astronomers pin down their redshifts.

In all, six previously unseen galaxies appear to sit more than 13 billion light-years distant.

Schaerer hinted that the new record might not hold the top spot for long.

"In principle one could be able to find galaxies up to redshift 16-18 from the ground," he said. "In practice this seems, however very difficult. I suspect that redshifts around 11-14 could be feasible, but very tough."

For now, he said, "we'll start to observe more galaxies between redshift 7 and 10, to be able to study their properties and to understand in more detail how they form and evolve. We've just started to see the tip of the iceberg."

Big business
Most of the most distant galaxies seen are known as a quasars, a class of very bright and compact objects thought to be powered by supermassive black holes.

Abell 1835 IR1916 is probably not a quasar, but it is experiencing a bout of intense star formation, the astronomers said. Yet the overall mass of the stars is estimated to be 10,000 times less than the mass of our much more mature Milky Way Galaxy.

Astronomers are not exactly sure how galaxies grew in the early years of the universe, but discoveries like this one should help them sort it all out. The leading theory holds that black holes and star formation go hand-in-hand, and that galaxy mergers played an especially important role early on in a universe that was smaller and far more crowded.

The latest discovery supports this big-business model of galaxy growth by acquisition, the astronomers said.

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