ebruary 14, 2008 Scientists Find Solar System Like Ours By DENNIS OVERBYE

Astronomers say they have 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.

The discovery, they said, means that our solar system might be more
typical of planetary systems across the universe than had been thought.

“It looks like a scale model of our solar system,” said Scott Gaudi
of Ohio State University. He led an international team of 69 professional
and amateur astronomers, who announced the discovery in a news conference
with reporters on Wednesday. Their results are being published Friday
in the journal Science.

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 about half the mass of the Sun, at about half the distances
that Jupiter and Saturn circle our own Sun.

Neither of the two giant planets is a likely abode for life as we know
it, but, as Dr. Gaudi pointed out, 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, “Right now in exoplanets we are on an
inexorable path to finding other Earths.” She praised the new discovery
as “a big step in finding out if our planetary system is alone.”

Since 1995, around 250 so-called 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 inside the orbit
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 stars should become perfectly aligned with the Earth, the gravity of
the nearer star can bend and magnify the light from the more distant one,
causing it to suddenly get much brighter for a few days.

If the alignment is especially perfect, any big planets attending the
nearer star will get into the act, adding their own little bumps 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. It
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-109L. The
next 10 days, as Andrew Gould of 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. Ms. McCormick,
who described herself as “an ordinary New Zealand mother,” said she
had done her observing with a 10-inch Meade telescope from a shed in
her back yard.

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 Bennett 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,” in the words
of Dr. Seager. The new system, she said, is just the tip of the iceberg
and the odds are that a lot of the ones that will be discovered could
be like ours.

Only six planets, including the new ones, have been discovered by
microlensing so far and the Scorpius event was the first in which the
alignment of the stars was perfect 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 Washinton, 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.”