Cosmic lenses magnify distant galaxies.

In the past 3 years, astronomers have discovered a universe of distant galaxies--some 600 starlit bodies that lie at least 8 billion light-years from Earth. They hail from a time when the cosmos was less than one-third its current age. As important as that population of galaxies has become for understanding the early cosmos, studying these objects has a drawback. Precisely because they lie so far away, distant galaxies appear too small and too faint for astronomers to observe in detail.

Thanks to the cosmic equivalent of a zoom lens, however, 15 newly discovered distant galaxies loom bigger and brighter than the rest. Magnified some 20 times, images of these galaxies have revealed a surprising secret. Each possesses a mammoth, high-speed wind that blasts material into space. These winds send out a hot gas rich in the materials that astronomers call metals--carbon, oxygen, silicon, and heavier elements.

The billowing winds are so vast that they could account for the entire quantity of metals in the young cosmos, says Tom J. Broadhurst of the University of California, Berkeley. He reported the findings this week in Paris at the Texas Symposium on Relativistic Astrophysics.

To probe the structure of distant galaxies, Broadhurst and his colleagues relied on a phenomenon that Albert Einstein pointed out in the 1930s. According to his theory of general relativity, gravity bends light and a massive object distorts and magnifies light from an object behind it.

The astronomers recently focused on three massive, relatively nearby clusters of galaxies known to act as gravitational lenses. They observed reddish arcs, indicating that the clusters bent light from distant galaxies. To examine the area, Broadhurst's team used a spectrograph on the world's largest visible-light telescopes, the twin Keck telescopes atop Hawaii's Mauna Kea. The spectra of the magnified images showed that the galaxies rank among the most distant known, residing at least 10 billion light-years from Earth.

The cosmic enlargement enabled the team to study light from the galaxies in unprecedented detail. The researchers found that the galaxies are about one-tenth the size of the Milky Way and form stars in a few, widely distributed clumps.

Broadhurst and Brenda Frye of Berkeley reported on the first of the galaxies they observed in the June 1 ASTROPHYSICAL JOURNAL LETTERS. After studying the spectra of light from several more galaxies, they have concluded that each has a superwind containing an abundance of metals. The winds stream out at speeds of 300 to 400 kilometers per second. Broadhurst suggests that type II supernovas, explosions of massive stars, produced both the metals and the powerful winds that drove them out into space.

The hot winds of ionized material from the galaxies "crashed into each other, and they polluted the whole of the intergalactic medium" of the early universe, Broadhurst says. He notes that this distribution could explain a longstanding puzzle: Why is the gas bathing today's clusters of galaxies so rich in metals? Broadhurst proposes that clusters incorporated metal-enriched gas that had been made by galaxies in the early cosmos.

According to a rival theory, galaxies produced the metals after they had already congregated in clusters. However, the supernova explosions required would have been so forceful that the metal-enriched gas generated would have been ejected from the clusters, Broadhurst says.

Garth D. Illingworth of the University of California, Santa Cruz and his colleagues published an earlier report on a distant galaxy magnified by a gravitational lens. Although the chance alignment between a distant galaxy and a lens is rare, he predicts that galaxies viewed that way will be "valuable pathfinders to star formation and the internal structures of [the first] galaxies."