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the parent star and the orbiting telescope. The job is not finished at
that point. There is a good deal of cross-checking involving both
other satellites and ground-based telescopes, because the dips in
luminosity may be due not to planets, but to (say) the less luminous
member of a pair of binary stars. It is best to combine the transit data
with those of gravitational wobble and, if possible, microlensing too
(although even in the star-filled heavens it is rare that one star lies
exactly
behind another).
The inventory of confirmed planets
156
out in space grows rapidly.
By the summer of 2013, from Kepler alone there were 134 confirmed
planets in 76 star systems—but also in excess of 3,000 exoplanet
candidates, still to be verified. It is a tricky task, as the small dips in
starlight can be confused with inherent fluctuations in the brightness
of stars.
Kepler's mission came to an end in 2013, after two of the spinning
wheels that kept it in position failed (the craft might still be put to
use to gather other data, however, even in its crippled state). COROT,
too, no longer functions. Like Kepler, it lasted a little longer than
planned (although for part of that time with only half its information-
gathering capacity), then suffered a final computer malfunction late
in 2012. A smaller machine than Kepler, it nevertheless discovered
over 30 exoplanets, with data from a couple of hundred more candi-
dates still being pored over.
What a variety these exoplanets show, although we hasten to add
that the variety we see today is a heavily biased one, even as the data
continue to flood in. It is easier to detect big planets than small ones,
and those that are close to their parent star than those that are far
away. Nevertheless, a pattern is emerging that suggests that our solar
system is by no means the standard model—and therefore that the
nature and chances of oceans and life (as we know them, at least) will
be different, out there.
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