“To do this we observe the
spectrum of the star in and out
of transit and subtract the two”,
explains Professor Hellier, “and the
difference will show tiny spectral
features caused by molecules in the
planet’s atmosphere which absorb
some of the star’s light.”
The WASP team pointed NASA’s
Spitzer Space Telescope at the
system WASP-12, and found that
the atmosphere of WASP-12’s
planet is dominated by carbonrich molecules, in contrast to
the oxygen-rich composition of
Earth. This finding of a planetary
system very different to our own
was reported in Nature, and led
to widespread publicity over the
possibility of planetary cores made
of diamond.
“WASP-South has now
found exoplanets around 60
different stars.”
Such is the potential of
‘transmission spectroscopy’ of
transiting exoplanets that both
NASA and ESA (European Space
Agency) are planning dedicated
space missions to investigate
exoplanet atmospheres. “Our task
is to find the best targets for those
missions”, states Professor Hellier,
“we’re aiming to find a range of
different-sized planets around
the brightest stars, because those
will be the systems that tell us
most about how planets form
and evolve.” The long-term goal
is the possibility of detecting
‘bio-marker’ molecules in exoplanet
atmospheres, molecules that could
only have arisen as a result of life
on those planets. It may be some
decades before it is technically
feasible to detect bio-markers
in the atmospheres of Earth-like
planets, but astronomers are
already well on that road.”
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