Light From A Distant Planet

Light emitted by a planet far beyond our Solar System has been identified
for the first time. The planet, illustrated in the above drawing, had its
light detected by comparing the brightness of only the parent star, when
the planet was behind the star, to the light emitted when both the planet
and its parent star were visible. The Earth-orbiting Spitzer Space Telescope
made the observation in infrared light, where the intrinsic glow of the planet
outshines the light it reflects from its central star. The direct observation
of light allowed a measurement of both the temperature and size of the planet:
HD 209458b. Planet HD 209458b was confirmed to be larger than expected for its
mass and on an orbit around its parent star that was unexpectedly close to a circle.