Results are in for the first search for Earth-sized planets
using MOST, Canada’s suitcase-sized space telescope. UBC astronomer
Jaymie Matthews will explain what has been "un-earthed"
at the Jan. 11 American Astronomical Society (AAS) Meeting
in Washington DC.
Taking advantage of the MOST (Microvariability & Oscillations
of STars) satellite’s unique ability to measure minute changes
in the brightness of stars, Matthews and other scientists
from the team put a star 160 light years away under an astronomical
"stakeout" to determine the existence of Earth-sized
extrasolar planets — or exoplanets — that would escape detection
by any other existing observatory.
MOST’s target was a Sun-like star called HD 209458, already
known to have a giant planet 15 times the diameter of Earth
and 220 times its mass. Named HD 209458b, the planet orbits
its parent star extremely closely — at only 1/20th of the
distance the Earth orbits the Sun.
By timing the regular faint dips in brightness as this planet
passes in front of the star, the MOST team can detect the
effects of the subtle gravitational tugs of other smaller
planets that might be hiding in the system.
"We were able to rule out Earth-sized planets in some
of the orbits where theorists believed they might be found,"
says Matthews, lead mission scientist of MOST, a Canadian
Space Agency mission.
The team’s analysis of reflected light signals of the planet
is also ruling out many possible models of its atmosphere
and cloud cover.
Likening the observations to making weather forecasts for
a planet 160 light years away, Matthews says the job poses
major challenges.
"Imagine trying to see a mosquito disappearing behind
a 400-Watt streetlamp, not at the next street corner or a
few blocks away, but 1,000 kilometers away," says Matthews.
"That’s equivalent to what we’re trying to do to detect
the planet’s eclipse in the HD 209458 system."
While the MOST team cannot yet rule out or detect Earth-like
planets in larger orbits around HD 209458, as the data accumulate
in the coming years, Matthews says MOST may be able to determine
whether or not there are potentially habitable worlds around
that star.
"Hugging so surprisingly close to its parent star, HD
209458b could never support life as we know it," says
Matthews. "But does it have any Earth-like neighbours
at a more comfortable distance? That’s a question that no
other observatory — on Earth or in space — can tackle at
the moment, except MOST."
MOST (Microvariability & Oscillations of STars) is a
Canadian Space Agency mission. Dynacon Inc. of Mississauga,
Ontario, is the prime contractor for the satellite and its
operation, with the University of Toronto Institute for Aerospace
Studies (UTIAS) as a major subcontractor. The University of
British Columbia (UBC) is the main contractor for the instrument
and scientific operations of the MOST mission. MOST is tracked
and operated through a global network of ground stations located
at UTIAS, UBC and the University of Vienna.
For more information, visit www.astro.ubc.ca/MOST/.
Note to editors:
- Prof. Matthews is available by phone from Washington DC
after 9:30 a.m. PST on Wednesday, Jan. 11. Please call 604.828.0272.
- A low resolution image illustrating the findings is available
at www.publicaffairs.ubc.ca/download.
For high resolution images or a video animation, please
contact Brian Lin, UBC Public Affairs, at 604.822.2234 or
cell 604.818.5685.
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