Traces of a distant extrasolar planet's hazy
red sunset have been detected for the first
time.
Astronomers
pointed the Hubble Space Telescope HD 189733b, a gaseous Jupiter-like world about
63 light-years from Earth, as it passed in front of its parent star to catch a
glimpse of the planet's atmosphere. Previous observations have not
revealed much about the planet's atmosphere, other than that it
has clouds.
"One
of the long-term goals of studying extrasolar planets is to measure the
atmosphere of an Earth-like planet [and] this present result is a step in this
direction," said Frederic Pont, an astronomer at the Geneva University
Observatory in Switzerland. Pont led the team of astronomers who made the new
Hubble observations.
"HD
189733b is the first extrasolar planet for which we are piecing together a
complete idea of what it really looks like," Pont said.
Starlight
passing through a planet's outer atmosphere can take on different colors as it
passes through different gases. In the case of HD 189733b, scientists said the
light traveling through the planet's hazy atmosphere appeared red in front of
its yellow star, which is about 76 percent of the diameter of the sun.
They
expected to see the fingerprints of sodium, potassium and water in the red
haze, but instead discovered iron, silicate and aluminum oxide (which sapphire
gems are made of). The composition is similar to Venus and Saturn's moon Titan—both
worlds with chokingly thick air.
So far, HD
189733b isn't thought to harbor any Earth-sized moons or Saturn-like rings, but
more powerful telescopes
of the future might detect them.
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