BOULDER,
Colorado – NASA's sharp-shooting Kepler spacecraft is ready to take its place
this week in the pantheon of planetary detection technologies.
It wasn't
long ago when a question mark loomed over astronomers pondering whether
other planets existed beyond our little family of solar system
worlds. Today, nearly
330 exoplanets have been discovered in the past 15 years - most of which are
gas giants with characteristics similar to Jupiter and Neptune.
It's a
little out of the astronomical limelight, but there are those that see planet
hunting as a "space race"...a worldwide competition to find
other Earths circling their respective stars.
In early
February, it was announced that the French COnvection ROtation and
planetary Transits
(CoRoT) spacecraft had discovered the smallest exo-planet yet, and with a surface to walk on
to boot, albeit blazingly boot-melting hot.
COROT-exo-7b is the
tiniest terrestrial planet ever detected outside the Solar System and
orbits a sun-like star.
"CoRoT is an excellent mission...a
complimentary mission to Kepler," explained William Borucki, Kepler's science
principal investigator at NASA's Ames Research Center at Moffett Field, Calif.
Those using
CoRoT have found that many of the stars they've surveyed are more variable than
expected, Borucki noted in a February 19 NASA press briefing on Kepler.
"So it's
going to be harder for us to find some of these planets. That's one of the reasons
they haven't found as many planets as they had hoped for at this time," Borucki
said. Still, the CoRoT team remained confident that their spacecraft will find
many more planets, he added.
Show
time for Kepler
Now it's
show time for NASA's Kepler, which is set
for a late-night liftoff on Friday, March 6.
It is billed
as the first mission with the ability to find planets like Earth - rocky
planets that orbit Sun-like stars in a warm and cozy zone where liquid water
could be sustained on the surface. Liquid water is viewed as crucial for the
formation of life.
"The CoRoT
mission continues to provide surprises with its latest discovery of a hot super
Earth with a 21-hour orbit. The Kepler mission looks forward to the
challenge of being the first to find an Earth-size planet in the habitable zone
of another star," Borucki advised SPACE.com.
There are a
host of differences between the two spacecraft.
The CoRoT
mission, along with its planet finding skills, is also designed to detect the subtle variation in a
star's light, caused by sound waves rippling across the surface. By doing this,
CoRoT will gain a detailed insight into the internal conditions of the star.
This technique is known as asteroseismology.
For the $600 million Kepler, there
is one goal: finding Earth-size planets in
the habitable zone of sun-like stars.
CoRoT launched in December 2006 and
in the last two years has led to the discovery of six giant planets and the recent
claim of a terrestrial planet in a 21-hour orbit with a diameter about 1.7
times that of the Earth.
More discoveries of hot terrestrial
size planets larger than the Earth are expected in the coming years. However,
because of CoRoT's small aperture and because it can only look at a star
field for five months before turning to another, it is not expected to discover
Earth-size planets in the habitable zone.
Kepler, meanwhile, is specifically
designed to discover dozens of Earth-size planets in the habitable
zone and hundreds near the habitable zone.
A comparison of Kepler to
CoRoT shows that Kepler has a 95-centimeter aperture, a field of view of
100 square degrees, 42 detectors, and monitors a field of view long enough to
find planets with periods as long as 1.5 years.
For CoRoT, it has a 27-centimeter
aperture, a field of view of four square degrees, and two detectors for
planet finding, and monitors a single field of view long enough to find planets
with periods no longer than 2.5 months.
Strong hints
At the ready to dive in on Kepler's
findings is James Kasting, a professor of geosciences at Pennsylvania State
University in State College, Pa. One of his space specialties is assessing
habitable zones around stars and the search for extraterrestrial life.
"I'm thrilled that Kepler is about
to launch," Kasting told SPACE.com.
Kasting
spotlighted CoRoT's recent finding of a super-Earth - about two Earth diameters
- circling a Sun-like star and having a surface temperature in excess of 1,500
degrees Celsius (2,700
degrees Fahrenheit).
"Kepler, if
it works, should find Earth-mass planets orbiting at one Astronomical Unit
around sun-like stars...assuming, of course, that they are present," Kasting
said. "As such it will give us strong hints as to whether other habitable
planets exist."
Looking
beyond Kepler and CoRoT, Kasting said what's really needed is a combination of
space-based astrometry and space-based direct imaging to find Earth-sized
planets around nearby stars and to study them spectroscopically.
"A positive
result from Kepler could help give us the momentum to get those missions funded,"
Kasting suggested.
Statistically
valid estimate
The French CoRoT
spacecraft is serving largely to whet our appetite for what Kepler will
discover, said Alan Boss in the Department of Terrestrial Magnetism at the Carnegie
Institution of Washington in Washington, D.C.
Boss is the
author of the newly published "The Crowded Universe - The Search for
Living Planets" – a book that points out that a "new space race" is
under way. The winner will claim victory, he writes, by discovering how
frequently Earth-like planets occur in our neighborhood of the Milky Way
Galaxy.
Boss
pointed out that the CoRoT spacecraft sports a smaller diameter (less than
one-third of Kepler), a smaller field of view for transit searches (about 20
times smaller than Kepler's), and has a restriction to staring for no more than
150 days at the same stars versus at least 3.5 years for Kepler.
All that
adds up to key facts: "CoRoT is able to find a few hot and warm super-Earths,
but not the habitable Earths that Kepler will discover," Boss told SPACE.com.
"Kepler should also discover enough Earth-like worlds - probably dozens - to
yield a good, statistically valid estimate of the frequency of Earths," he
said.
"CoRoT is
wonderful," Boss concluded, "but Kepler will be 'wonderfuller!'"
High
hopes
Meanwhile,
hopes are high for Kepler here at the Boulder, Colorado-based Ball Aerospace
& Technologies Corporation. Ball is the firm responsible for developing the
planet-hunting Kepler flight system and is supporting mission operations.
Working
closely with Ball in operating the spacecraft is a team of 20 students and 16
professionals from the neighboring University of Colorado, Boulder's Laboratory
for Atmospheric and Space Physics (LASP).
There were
1,350,000 labor hours here at Ball, in-house, to build that machine," said John
Troeltzsch, Ball Aerospace Program Manager for Civil Space Systems. "Kepler is
a very unique NASA telescope in that we have a huge field of view," he told SPACE.com.
Troeltzsch
said that Kepler is "perfectly optimized" to search for
Earth-size planets in the habitable zone of their parent stars.
While
Kepler is on tap for a three-and-a-half year prime mission, the hope is for
extending its planet-searching duties.
"The longer
you go...the more science you're going to get," Troeltzsch said. "We get up
there and we're finding planets, there's really going to be, I think, a lot of
compelling reasons to extend the mission."
Predicted Troeltzsch:
"I think we're going to find a lot of planets. It's going to change the way
people think about space. And I also think it's going to change the way NASA's
targeting future missions to do follow-up."
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