On the horizon

A frozen world found more than 8 billion miles from Earth is believed to be the farthest known object in our solar system, scientists say. The discovery of Sedna, a "planetoid" of rock and ice between 800 miles and 1,100 miles in diameter - three-quarters the size of Pluto - was announced by Mike Brown, an astronomer at the California Institute of Technology who led the NASA-funded team that discovered it. Sedna is the largest object found orbiting the sun since the discovery of Pluto in 1930 and lies more than three times as far from the sun as Pluto.

Scientists estimate the temperature on the planetoid never rises above 400 degrees below zero F., making it the coldest known body in the solar system. Sedna follows an elliptical path around the sun, which takes 10,500 years to complete. Brown believes Sedna is the first known member of the long- hypothesized Oort Cloud, a repository of comets that swoop past Earth.

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less warming from water vapor

Some climate forecasters may be over- estimating increases in global temperatures. A new study found that such forecasts are based on an overestimation of the amount of water vapor that will enter the atmosphere as Earth warms.

Researchers at the University of Maryland, NASA, and the New Mexico Institute of Mining and Technology verified that water vapor is increasing in the atmosphere as the surface warms. But the increases were not nearly as high as many widely used climate-forecasting computer models have assumed, the researchers said.

The increase of water vapor is a key debate among scientists. Greenhouse gases trap heat, increasing evaporation from oceans and causing more water to evaporate. The rise in vapor leads to a further increase in temperatures. General-circulation models, the primary tools scentists use to forecast climate, predict Earth's surface will warm nearly twice as much over the next 100 years as do models that contain no water-vapor feedback. The new findings, which measured vapor worldwide and showed significantly less of it, will help make climate models more accurate.

RIght whales rebound

There is growing optimism that the endangered North Atlantic right whale can come back from the edge of extinction. The new hopes are prompted by observations of the whales in their only known winter calving area, off the coast of Georgia and northern Florida.

Scientists now believe that a previously undocumented group of as many as 17 female right whales has started using the calving grounds. They're also encouraged by the number of right whales born recently. So far this season, 13 newborns have been seen in Georgia and Florida waters. Only one calf was reported in 2000. About 300 North Atlantic right whales remain, making them one of the most endangered species.