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On the horizon: News from the frontiers of science

Sugar-powered cars, a downside to bird feeders, and the dark core of Omega Centauri.

Sugar-powered Cars

Pranksters put sugar in gas tanks to foul engines and halt cars in their tracks. But a Virginia Tech scientist is developing a way to run cars on sugar.

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Y.-H. Percival Zhang's "sweet engine" runs on hydrogen made from starch, a clean-burning and potentially renewable alternative to fossil fuels.

Although hydrogen fuel cells are much more efficient than combustion engines, hydrogen is difficult to transport, store, and distribute – as well as expensive to produce. But Professor Zhang's method, which he presented April 9 at the national meeting of the American Chemical Society in New Orleans, circumvents the need for transportation and storage by turning sugar into fuel in the car on an as-needed basis.

It produces three times more hydrogen than current anaerobic fermentation methods. "This is the highest energy efficiency in the world," says Zhang, an assistant professor at Virginia Tech in Blacksburg, Va.

The secret? A stew of naturally occurring enzymes that, at 86 degrees F., create hydrogen and CO2 from a water-sugar mixture. The process could be market-ready in 5 to 10 years, says Zhang.– Moises Velasquez-Manoff

A downside to bird feeders

Backyard bird feeders have become almost as ubiquitous as garden hoses. One result: the northern cardinal's range has grown significantly since the early 1960s. Yet scientists know little about the long-term effect the explosion in feeders is having on bird populations.

So a group of biologists in Britain has pulled together a look at what is known. They find that most of the effects from supplemental feeding seem to be positive. But seed-laden feeders have the potential to trigger long-term changes in species' range and breeding patterns.

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In reviewing studies from the past 30 years, the team finds that supplemental feeding led female birds to lay eggs significantly earlier than is typical for their species. For some birds, such as Florida scrub jays, this put the young out of sync with the natural food sources they needed at that stage of their development. For one species of flightless parrot in New Zealand, a feeding campaign to increase the birds' population actually led to the birds hatching more males over time than females.

The biologists add that some of the less desirable effects of supplemental feeding could be reduced if more people follow best-feeding practices, such as those outlined by Project Feeder Watch, led by researchers as Cornell University. The results appear in the current issue of Frontiers in Ecology.– Peter N. Spotts

The dark core of Omega Centauri

The largest, brightest star cluster in the night sky appears in the constellation Centarus. And astronomers are closing in on solving its centuries-long identity crisis. What Ptolemy once pegged as a single star and Sir John Herschel saw as a globular cluster (he was getting warmer) now appears to be the leftover core of a dwarf galaxy that the Milky Way gobbled up.

Globular clusters are groups of up to 1 million stars that are born so close together that their combined gravity binds them in a group, in contrast to open clusters such as the Pleiades, where the stars all move away from each other. But Omega Centauri, as the cluster in question is known, was odd, compared with other globulars: It rotates faster, has a flatter shape, and contains far more mass. Its stars display traits that imply two bursts of star formation – one when it formed, another when it became the Milky Way's snack.

An international team of astronomers, led by Eva Noyola at the Max Planck Institute for Extraterrestrial Physics in Germany, measured the motion of the cluster's stars. The innermost stars were moving unusually fast, given the overall mass of the stars in the cluster. Something really massive must lie at the cluster's heart, they reasoned. The most likely explanation: A rare, intermediate-class black hole – far more hefty than black holes that form from collapsed stars, but far less massive than the black holes found at the cores of large galaxies. If the hidden actor is a black hole, the team figures it tips the scales at 40,000 times the mass of the sun. The results have been accepted for publication in the Astrophysical Journal.– P.N.S.