Two planets proportionally similar to Jupiter and Saturn are
orbiting a star in a constellation called Scorpius, which is 5,000 light years,
or 30 quadrillion miles, away.
The finding suggests that solar systems patterned like ours
may be common, something astronomers have long believed to be true, said Scott
Gaudi, assistant professor of astronomy at Ohio State University and lead
author of the study. The study was published in the Feb. 15 issue of the
"I think this is very encouraging in terms of the hope
that there are other solar systems like our own out there," Gaudi said. "This
is a good step in the direction of trying to answer these questions."
Scientists detected the planets using a technique called "gravitational
microlensing," which required constant nighttime monitoring of the
faraway constellation over a 10-day span. To do so, researchers relied on
amateur astronomers Jennie McCormick and Grant Christie, both based in Auckland, New
Zealand, to collect data during the American
Microlensing, long considered the "poor cousin" of
planet-finding techniques, uses Einstein's theory of relativity to find massive
objects in outer space. When a close and a distant star align, the foreground
star acts as a lens, magnifying the background star. Gravity of the planets near the background star further distorts
the image. Scientists calculate the mass of the planets by measuring the extra
distortions in that background star.
"In general, the bigger
the planet, the larger the area is that it distorts," said Andrew Gould,
professor of astronomy at Ohio
State, and one of the
study's co-authors. "If the planet is bigger, it will have fluctuations
that last longer."
This discovery marks the first time microlensing has been used
to find more than one planet. Only four other planets have been detected by
this method, which is a tricky and time-consuming process, also requiring tens
of thousands of hours of mathematical modeling.
"There's a lot of triage involved," Gould said. "It's
really the result of an incredibly chaotic process." Gould also heads the
MicroLensing Follow-Up Network, a collaboration of professional and amateur
astronomers who assist in collecting data for microlensing events.
There is much that is still unknown about the planets. Astronomers
don't know how big they are, what they are made of, or whether other smaller
planets orbit the same host star. Any planet the size of earth would have
escaped detection by the team because it would be too small to be seen with current
technology at that distance.
"To see an earth directly would be like trying to find a
firefly within one inch of a search light," said Sara Seager, professor of planetary science at the Massachusetts
Institute of Technology.
But astronomers do know the mass of both planets and the mass
of the star that they orbit. They know that these planets - believed to be gas
giants - are the same distance from their sun as Jupiter and Saturn are to
ours. And like Jupiter compares to Saturn, the larger planet is triple the size
of the other.
"The star itself is smaller and dimmer than the sun,"
Gaudi said. "The planets are also smaller. But the amount of sunlight is
not that different than ours, because the planets are closer."
Microlensing is particularly useful when objects are too far away to be
located by more traditional methods, such as radial velocity, or the "wobble"
So far, Scientists have found about 270 planets and about 25
multiple-planet systems, mostly using the wobble method. Seager said most of
these planets "are just crazy" -- giants compared to earth and clustered
closer to their sun than those in our solar system.
Scientists believe this is because, the wobble method, by its
very nature, is more sensitive to finding planets that sit closer to their parent star.
"[Microlensing] is the only technique that can find
Saturn-like planets at Saturn-like distances from the star," Seager said. "We're
seeing a triumph of a new technique and a vindication for people working so
hard to find planets that no other technique can find."