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.”

Via New York Times