On the horizon

Hurricanes: fiercer, less frequent

Hurricanes are growing stronger worldwide, feeding off of ever-warmer water in the tropical oceans, according to a new study by a team of scientists at Georgia Tech in Atlanta and the National Center for Atmospheric Research in Boulder, Colo.

The team found that over the past 35 years, the average number of Katrina-like category 4 and 5 storms grew from 10 a year during the 1970s to 18 a year since 1990. And these dynamos represent a larger share of tropical cyclones - from about 20 percent of all hurricanes and typhoons in the '70s to 35 percent today.

Data also present a puzzle: Over the past decade, the average number of hurricanes worldwide has eased and they don't last as long, even though the waters that feed them have gotten warmer. The one exception is the Atlantic Basin, where storms have grown more frequent and last longer.

The results, which appear in the current edition of the journal Science, follow on the heels of a study published in July that found similar trends in storm strength, using a different measure.

An orphan in space

Astronomers are puzzling over an orphan of prodigious proportions: a super-massive black hole without a galaxy to call home, some 5 billion light years away.

An international team of astronomers stumbled across the orphan during a survey of quasars - distant sources of intense radiation. The radiation comes from galaxies containing active super-massive black holes at their cores. The team is convinced that their solo black hole lacks a galaxy - at least of the sort astronomers are used to seeing. The team scoured the space around the black hole with the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope in Chile, which would have detected a host galaxy.

Based on a blob of glowing gas and a severely disrupted galaxy near the black hole, the team suggests that the black hole collided with the jumbled galaxy roughly 100 million years ago. But that leaves unanswered the question of what happened to the material that should have been the black hole's host galaxy. One intriguing possibility, the team says: The galaxy hosting the black hole might have been made of dark matter, a form of matter that so far has eluded detection except by its indirect effects on galaxies that astronomers see.

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