Over the last few weeks, astronomers announced not one but two
extraordinary discoveries in the ongoing search for planets orbiting
stars beyond the sun. The first was a world about the size of
Neptune, 5,000 light-years away, whirling around in a solar system
with four stars. It's something like Luke Skywalker's home world of
Tatooine in the "Star Wars" movies, except that fictional planet
sported only two suns.
The second was an Earth-size planet right next door in the Alpha
Centauri system - three stars that orbit one another not thousands
or hundreds but a mere four light-years from our solar system. That
makes it not just the nearest "new" planet ever found but the
nearest that could be found. (It isn't for nothing that so many sci-
fi authors - although not George Lucas - have set their tales in
the Alpha Centauri system.) With a surface temperature of 2,000
degrees or so, this planet's surface is probably molten, but its
presence implies, tantalizingly, that there could be more.
All of this is exciting and wonderful, but it's a far cry from
the discoveries astronomers thought they would be making by now.
Back in the mid-1990s, when the first "exoplanets" (extrasolar
planets) were found in distant star systems, NASA talked boldly
about the new generation of powerful telescopes it was planning to
build, in large part to hunt for alien worlds, especially those in
balmy, life-friendly orbits.
By the early 2000s, something called the Space Interferometry
Mission, or SIM, was going to measure the nearly imperceptible side-
to-side wobbles caused by the gravity of Earth-size planets, tugging
their stars first one way, then the other as they orbited. By 2007,
the original version of the James Webb Space Telescope, designed to
be bigger and more powerful than the Webb scope now under
construction, was supposed to be taking direct images of giant
planets, along with other astronomical duties.
And by 2020 or so, the Terrestrial Planet Finder, or TPF, would
be imaging true Earth "twins," scanning their atmospheres for gases
that might betray biological activity.
As of today, however, SIM has been canceled; the smaller, less
powerful Webb will launch by 2018 perhaps; and the TPF has been put
on the back burner, maybe permanently. These disappointments have
partly to do with NASA's ever-shrinking science budget, but SIM and
TPF were also torpedoed by internal squabbling among scientists who
disagreed about the best designs and about whether SIM was vital or
unnecessary.
Yet even without the scopes they hoped for, astronomers are
finding planets by the carload, using the Kepler space telescope,
launched in 2009, and even small, ground-based instruments. Rather
than wait for NASA to come through with expensive new toys,
innovators like Harvard University's David Charbonneau; William J.
Borucki of the NASA Ames Research Center in the Bay Area; and Michel
Mayor at the Geneva Observatory in Switzerland kept pushing existing
the science to its limits, and then pushing again.
Borucki, for example, lobbied for more than a decade to have NASA
approve his Kepler mission, which is designed to look for the faint
dip in light that occurs when an exoplanet passes in front of its
star. It was a simpler and cheaper planet discovery method than SIM
and the rest, but the agency kept finding fault with his proposal,
so he answered their objections and re-proposed it five times. Since
its launch, Kepler has found more than 2,000 probable planets.
Charbonneau chose to look for dips in starlight as well, but from
the ground; his innovation was to look at dim red stars, figuring a
dip in light would be easier to spot if the star was dimmer to begin
with. And Mayor took his 1990s-era instruments, which look for
subtle changes in a star's color as a planet yanks it back and forth
during the planet's orbit, and refined them beyond what anyone
thought was technologically possible. It was his team that found the
Alpha Centauri planet.
The result: While the telescope makers dithered, the roster of
planets has exploded, from just one in 1995 to 800 known alien
worlds, and an additional 2,300 - provisionally identified by
Kepler - that are waiting to be confirmed by further observations.
Some of these provisional planets come from an unlikely source:
Citizen scientists on the website planethunters.org, scouring Kepler
spacecraft data, were the ones who flagged the new four-star planet
in Kepler's database, after the professional scientists had missed
it.
This sort of scrappy ingenuity has kept the field of
exoplanetology hopping with new discoveries, astonishing even the
most seasoned scientists with the endless surprises the cosmos seems
to hold. But just imagine the discoveries that would be happening
with a NASA science budget that could keep up with astronomers'
dreams.
Michael D. Lemonick is a senior writer at Climate Central and the
author of "Mirror Earth." He wrote this for the Los Angeles Times.
