Wednesday, March 23, 2005
I see planets
Jacob
For the first time, astronomers have directly detected radiation from planets that orbit distant stars. So far, more than 130 such planets have been identified indirectly, but with a new technique researchers have "seen" heat from two giant planets close to their stars.
One planet, known as TrES-1, is 489 light years away in the constellation Lyra. The other, HD 209458b, is 153 light years off, in the constellation Pegasus.
"It's an awesome experience to realise we are seeing the glow of distant worlds," said David Charbonneau, of the Harvard Smithsonian Centre for Astrophysics, who, with colleagues, reports today in the Astrophysical Journal. A second team, at Nasa Goddard Space Flight Centre, reports in Nature online today.
The two groups of scientists used different instruments aboard Nasa's Spitzer space telescope, but a similar approach.
Until 1995 the only planets known in the universe were the nine orbiting the sun. Then astronomers studying gravitation wobbles in faraway stars deduced they were seeing evidence of giant planets orbiting close to parent stars.
Any planet is 10,000 times less bright than its parent star, so there would be no hope of detecting visible light. But Drake Deming, of Nasa, and Dr Charbonneau realised that they might detect heat.
They measured changes as each planet passed in front of and then behind its star, and found that HD 209458b had a temperature of 857C (1,574F) and TrES-1 was at 787C.
"The one thing [these planets] cannot hide is their heat," said Dr Charbonneau.
