On the horizon

First 'exoplanet' seen from earth

It was a "Kodak moment" - the first confirmed direct image, using earthbound telescopes, of a planet orbiting another star, say astronomers with the European Southern Observatory in Chile.

Direct imaging has been a holy grail in the hunt for these "exoplanets." It's largely been thought the province of a coming generation of orbiting telescopes. Several other groups have tried from the ground, with inconclusive results.

The ESO team first detected the object in April 2004 near a brown dwarf star 200 light-years away in the constellation Hydra. Even with help from the Hubble Space Telescope, it was too tough to tell if the object, five times as massive as Jupiter, was a companion to the star. In February and March, the team turned ESO's Very Large Telescope on the pair. They found that the two were moving against background stars, confirming companionship. The work is set to be published in the journal Astronomy and Astrophysics.

Atmosphere as heat sponge

Earth is soaking up more of the sun's energy than it sends back into space - another indicator that the climate is warming, largely due to human activity.

That's the conclusion of a new study by a group of scientists from NASA, Columbia University, and the Lawrence Berkeley National Laboratory. The study compares computer simulations of Earth's radiation balance against measured increases in upper-ocean temperatures over the past decade. The measurements confirm the simulations' result that the planet is retaining about 0.85 watts per square meter more energy than it radiates back into space. The team estimates that global average temperatures would continue to rise another 0.6 degree Celsius (1 degree F.) even if humans hit the brakes on greenhouse-gas emissions today - largely because of the oceans' enormous capacity to retain, then release, heat. The results appear on the journal Science's "Sciencexpress" website.

Near moon with a far-out past

When the Cassini spacecraft swung past Saturn's moon Phoebe last June, scientists knew they were looking at an odd duck. They just didn't realize how odd.

Phoebe's orbit is unusual compared with Saturn's other moons - backward and highly elliptical. Early descriptions of Phoebe's composition also implied that it wasn't built of material that would have been found in its neighborhood.

Phoebe's cosmic kin are more likely to be Pluto or Triton than the moons of Saturn, report two of the orbiter's research teams, after studying measurements taken during Cassini's flyby. Phoebe's rock-to-ice ratio suggests that it formed in the more distant reaches of the outer solar system occupied by what is now known as the Kuiper Belt.

That would mean astronomers have gotten their first close look at a Kuiper Belt object. Its surface composition is among the most varies of any object yet seen in the solar system, say the researchers.

Their results appear in Thursday's edition of the journal Nature.

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