In November 2001, it was announced that the first chemicals had been detected in the atmosphere of an extrasolar planet. This was done by looking at the system as the planet transited (or passed in front of) the star. The light from the star will change by a tiny amount when part of it passes through the atmosphere of the planet and by making extremely sensitive observations this tiny change can be detected. The element that was detected was sodium, and from prior observation the planet is known to be about 70% the mass of Jupiter and so close to its star that its atmosphere is heated to 1100 Celsius (2000 Fahrenheit)!