Smaller Version of the Solar System Is Discovered
- From: Florida <demeter547opine@xxxxxxxxx>
- Date: Sat, 16 Feb 2008 10:14:30 -0800 (PST)
http://www.nytimes.com/2008/02/15/science/space/15planets.html?em&ex=1203310800&en=92443ad116b59163&ei=5087%0A
The New York Times
February 15, 2008
Smaller Version of the Solar System Is Discovered
By DENNIS OVERBYE
Astronomers said Wednesday that they had found a miniature version of
our own solar system 5,000 light-years across the galaxy -- the first
planetary system that really looks like our own, with outer giant
planets and room for smaller inner planets.
"It looks like a scale model of our solar system," said Scott Gaudi,
an assistant professor of astronomy at Ohio State University. Dr.
Gaudi led an international team of 69 professional and amateur
astronomers who announced the discovery in a news conference with
reporters.
Their results are being published Friday in the journal Science. The
discovery, they said, means that our solar system may be more typical
of planetary systems across the universe than had been thought.
In the newly discovered system, a planet about two-thirds of the mass
of Jupiter and another about 90 percent of the mass of Saturn are
orbiting a reddish star at about half the distances that Jupiter and
Saturn circle our own Sun. The star is about half the mass of the Sun.
Neither of the two giant planets is a likely abode for life as we know
it. But, Dr. Gaudi said, warm rocky planets -- suitable for life --
could exist undetected in the inner parts of the system.
"This could be a true solar system analogue," he said.
Sara Seager, a theorist at the Massachusetts Institute of Technology
who was not part of the team, said that "right now in exoplanets we
are on an inexorable path to finding other Earths." Dr. Seager praised
the discovery as "a big step in finding out if our planetary system is
alone."
Since 1995, around 250 planets outside the solar system, or
exoplanets, have been discovered. But few of them are in systems that
even faintly resemble our own. In many cases, giant Jupiter-like
planets are whizzing around in orbits smaller than that of Mercury.
But are these typical of the universe?
Almost all of those planets were discovered by the so-called wobble
method, in which astronomers measure the gravitational tug of planets
on their parent star as they whir around it. This technique is most
sensitive to massive planets close to their stars.
The new discovery was made by a different technique that favors
planets more distant from their star. It is based on a trick of
Einsteinian gravity called microlensing. If, in the ceaseless shifting
of the stars, two of them should become almost perfectly aligned with
Earth, the gravity of the nearer star can bend and magnify the light
from the more distant one, causing it to get much brighter for a few
days.
If the alignment is perfect, any big planets attending the nearer star
will get into the act, adding their own little boosts to the more
distant starlight.
That is exactly what started happening on March 28, 2006, when a star
5,000 light-years away in the constellation Scorpius began to pass in
front of one 21,000 light-years more distant, causing it to flash.
That was picked up by the Optical Gravitational Lensing Experiment, or
Ogle, a worldwide collaboration of observers who keep watch for such
events.
Ogle in turn immediately issued a worldwide call for continuous
observations of what is now officially known as OGLE-2006-BLG-109. The
next 10 days, as Andrew P. Gould, a professor of mathematical and
physical sciences at Ohio State said, were "extremely frenetic."
Among those who provided crucial data and appeared as lead authors of
the paper in Science were a pair of amateur astronomers from Auckland,
New Zealand, Jennie McCormick and Grant Christie, both members of a
group called the Microlensing Follow-Up Network, or MicroFUN.
Somewhat to the experimenters' surprise, by clever manipulation they
were able to dig out of the data not just the masses of the interloper
star and its two planets, but also rough approximations of their
orbits, confirming the similarity to our own system. David P. Bennett,
an assistant professor of astrophysics at the University of Notre
Dame, said, "This event has taught us that we were able to learn more
about these planets than we thought possible."
As a result, microlensing is poised to become a major new tool in the
planet hunter's arsenal, "a new flavor of the month," Dr. Seager said.
Only six planets, including the new ones, have been discovered by
microlensing so far, and the Scorpius event being reported Friday is
the first in which the alignment of the stars was close enough for
astronomers to detect more than one planet at once. Their success at
doing just that on their first try bodes well for the future,
astronomers say.
Alan Boss, a theorist at the Carnegie Institution of Washington, said,
"The fact that these are hard to detect by microlensing means there
must be a good number of them -- solar system analogues are not rare."
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