Science notes

New light on a dark patch of cosmic history

Astronomers are slowly lifting the veil from a period of cosmic history dubbed "the dark ages."

At a recent meeting of the American Astronomical Society in Seattle, two teams of researchers reported that they had spotted fledgling galaxies, stars, and quasars that may have helped end a 1 billion-year period when light from these objects was obscured by a universe brimming with hydrogen atoms.

These objects appear "at the boundary of the directly observable universe," says Arizona State University astronomer Rogier Windhorst, whose group detected the stars and minigalaxies with the Hubble Space Telescope.

Current theories hold that the first atoms - mostly hydrogen - started forming roughly 300,000 years after the universe began, some 14 billion years ago, in an enormous release of energy known as the Big Bang. As the universe cooled and the first stars and baby galaxies formed, researchers hold that their light was too feeble to ionize hydrogen, which would have allowed their light to pass freely.

As their numbers grew, however, their combined ultraviolet light also grew intense enough to ionize hydrogen in a sustained way. To earthbound observers, it's as though they are peering through breaks in an increasingly threadbare cosmic fabric.

Using the spectra of light from seven quasars shining from within the "dark ages," a second team says it has spotted the primitive hydrogen fabric itself, as well as heavier elements forged in stars' fusion furnaces.

Ocean's magnetic fields detected by satellite

Oceans can be attractive for many reasons - one of them is magnetism.

Research in the current issue of the journal Science has shown for the first time that the ocean's magnetic fields can be detected via satellite. The research also raises the potential to use the oceans' magnetic fields as a means of tracking large-scale ocean circulation patterns.

Variations in these patterns over time represent "a key factor in addressing climate and global change concerns," notes Robert Tyler, a scientist with the University of Washington's Applied Physics Laboratory, whose team conducted the research.

He explains that salts in seawater dissolve to form ions - electrically charged atoms. As the ions are carried by ocean currents or shifted by tides, Earth's overall magnetic field goes to work, affecting them in various ways. One effect encourages the ions to gather themselves into dense patches of electrical charge. The charge can build to the point where it short-circuits into surrounding water or into the sea floor. Each discharge, a brief burst of flowing electrical current, sets up its own magnetic field.

These fields are weak - on the order of one-thousandth of Earth's magnetic field. Dr. Tyler and his colleagues teased them out of satellite data by running computer simulations of what the magnetic signals from lunar tides would look like, then comparing that pattern with magnetic-field records from the German CHAMP satellite, launched in 2000. The predicted patterns closely matched the satellite data.

The next step, he concludes, is to examine the feasibility of using this approach to tracking ocean flow from space.

Aerosols in airliner exhaust may cool atmosphere

Become a frequent flier to combat global warming?

That could be one tongue-in-cheek conclusion from research conducted in Italy and the Netherlands. As commercial airliners rumble through the sky, they not only can leave a sparkling white contrail behind them; they also spew tiny sulfate aerosols into the atmosphere.

A team led by Giani Pitari, of the University of L'Aquila in Italy, studied the impact these aeronautical aerosols have on atmospheric chemistry. Using computer simulations that track the direct and indirect chemical effects of airliner exhaust, they found that the sulfate aerosols would tend to cool the surface while warming the upper atmosphere - similar to the effect of sulfate aerosols from volcanic eruptions.

Released into the atmosphere at airliner cruising altitudes, however, these particles also could slow the rate of recovery of stratospheric ozone, the researchers say, because the aerosols serve as platforms for ozone- eating chemical reactions.

The work appears in the Jan. 6 issue of Geophysical Research Letters.

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