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Alt 07.06.2004, 13:52   #13
Desert Rose
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Man will den morgigen Venustransit dazu benutzen um die Technik, auf der Suche von Extrasolar Planeten, zu verfeinern.

Extrasolar planet hunters eye Venus transit

09:00 06 June 04

NewScientist.com news service

Extrasolar planet hunters will set their sights close to home on Tuesday when Venus passes in front of the Sun for the first time since 1882.

About 120 planets have been discovered orbiting other stars. Three of these were revealed because they dimmed their stars' light during transits, which also gave information about the planets' masses. And future space missions such as NASA's Kepler, due to launch in 2007, aim to find many more transits by monitoring 100,000 Sun-like stars.

The transit of Venus will dim the Sun's light by just a tenth of one per cent but the data astronomers hope to gather will help interpret future extrasolar searches. "Extrasolar planets are unique among astronomical objects because there are local counterparts to study," says Sara Seager, who models the atmospheres of extrasolar planets at the Carnegie Institution in Washington, DC.

Seager's colleague Dan Kiselman will use the Swedish one-metre Solar Telescope in the Canary Islands to look for carbon dioxide in Venus's atmosphere during the transit. The gas comprises 97 per cent of the planet's atmosphere, but Seager says: "We designed the experiment to detect something we know is there. If we're going to interpret extrasolar planets, we want to make sure the models are correct."

The team will also look for trace amounts of sodium or potassium in the planet's atmosphere. These elements - the remains of burned-up meteorites - float in Earth's upper atmosphere but have never been seen on Venus. Seager hopes backlighting by the Sun may reveal the elements' faint absorption signal.
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