"Boggle" might be the perfect name for the planet Notre Dame's
David Bennett and an international team of astronomers discovered
recently. The distant world, estimated to be one-and-a-half times
the size of Jupiter, is so far away from Earth and the means of
its discovery is so novel that it boggles the mind.
The planet is the most distant from Earth ever discovered --
17,000 light years away, near the center of our galaxy -- and
the first to be found with a controversial technique called microlensing.
Until now most of the more than 100 known planets were discovered
by observing a telltale wobble in a star's rotation caused by
a nearby orbiting planet. The "wobble" technique works up to 170
light years away.
Microlensing is a clever idea based on an insight of Albert
Einstein's that allows scientists to use the universe itself as
a kind of telescope. According to Einstein, massive objects, such
as stars and planets, curve space and warp time in their vicinity.
Thus light travels around the curved space in a way similar to
how a magnifying glass bends light.
With that in mind, astronomers have been scanning the sky looking
for instances where one star passes in front of another as seen
from Earth. In that particular case the gravity of the foreground
star can bend and focus the light of the background star. If the
star has a planet revolving around it, a signature pattern of
brightening and dimming will occur. The phenomenon is so rare
-- Einstein believed it never would be observed -- that Bennett
says astronomers had to look at hundreds of millions of stars
to find the microlensing alignment of star and planet. The technique
is controversial because it is difficult to verify since the microlensing
event happens only once.
In summer 2003 a team of U.S. and Polish scientists using a
telescope in Chile noticed a microlensing event in the constellation
Sagittarius. When Bennett's group, composed of scientists from
the United States, New Zealand and Japan, looked at its data for
the same event captured from a telescope in New Zealand the scientist
detected the signature "brightness blips" indicating the presence
of a planet.
Bennett's group has a proposal pending with NASA to search for
stars with planets using an orbiting wide-angle telescope half
the size of the Hubble telescope. The new telescope, called the
Microlensing Planet Finder (MPF), would have the ability to scan
millions of stars every night looking for the telltale microlensing
signature of a distant planet. If the MPF is funded by NASA, the
Notre Dame research associate professor of physics will be the
lead scientist for the project.
(July 2004)
