Amateur and Professional Astronomers Team to Find New Exoplanet

http://www.cfa.harvard.edu/press/pr0514.html

Harvard-Smithsonian Center for Astrophysics
Release No.: 05-14
For Release: May 23, 2005

Amateur and Professional Astronomers Team to Find New Planet

Cambridge, MA--For the first time, amateur and professional astronomers
have teamed up to discover a new planet circling a distant star. The
planet was detected by looking for the effect of its gravitational
field
on light from a more distant star, a technique known as microlensing.
It
is only the second world to be discovered using the microlensing
technique. Gravitational microlensing offers the potential for
detecting
Earth-mass planets using existing or near-future technologies.

"This discovery is the tip of the iceberg for microlensing searches,"
said astronomer Scott Gaudi (Harvard-Smithsonian Center for
Astrophysics). "With improving technologies and techniques, the first
Earth-sized planet may be found by microlensing."

"If an Earth-mass planet was in the same position [as the planet we
found], we would have been able to detect it," agreed professor Andrew
Gould (Ohio State University), a member of the team who made the
discovery.

Microlensing searches scored their first discovery only last year. This
second find confirms the power of this planet-hunting technique and
heralds the beginning of routine planet detection by microlensing.

"This is the beginning of the age of microlensing. We expect many more
discoveries in the coming years," said Gaudi.

The newfound planet weighs approximately 3 times as much as Jupiter and
probably orbits a star similar to the sun. At the time of its
discovery,
it was located about 3 times the earth-sun distance from its host star.
Although its orbit is uncertain, the possibility of a "hot Jupiter"
that
revolves very close to its star was ruled out.

Both the planet and its star are located about 15,000 light-years from
the earth, making this world one of the most distant ever discovered.
Gravitational microlensing offers unique advantages for astronomers
hunting planets: not only can it find more distant worlds than more
common techniques such as the radial velocity, or "wobble," method, but
microlensing also is more sensitive to smaller worlds.

"Even the signal from an earth-mass planet can be relatively large -
tens of percent, which is very detectable," said Gaudi.

Gaudi played a key role in confirming the new planet. Although a
microlensing event can last days, the presence of a planet will affect
the signal for only a day or so. Therefore, data must be analyzed as
quickly as it is gathered to identify the events that merit close
watching.

"I was in Korea when we saw that this event was doing something strange
and different," said Gaudi. "When I first looked at the deviation, I
thought it looked like a planet. As soon as I got home to Cambridge, I
downloaded the data and worked on it for 12 hours straight to analyze
it. I figured out that there was no other explanation. It had to be a
planet."

Detecting the planet's signal required obtaining data from many
observatories around the world so that the microlensing event could be
monitored around-the-clock. Gaudi is a member of the Microlensing
Follow
Up Network (MicroFUN), which is headed by Gould.

"There was an old saying that the sun never set on the British Empire.
You could say that the sun never rises on our collaboration!" said
Gaudi.

Two New Zealand amateur astronomers belong to the MicroFUN
collaboration-Grant Christie of Auckland, who used a 14-inch-diameter
telescope, and Jennie McCormick of Pakuranga, who used a 10-inch
telescope. Data from both telescopes proved crucial in detecting the
planet, and both observers share co-authorship on the paper announcing
the find.

"These amateur astronomers work all day, then go home and observe all
night," said Gaudi. "Their contribution is a testament to how far
amateur astronomers have come. It speaks highly of their dedication to
the field."

The microlensing event was detected and monitored extensively by the
Optical Gravitational Lensing Experiment, or OGLE, headed by Andrzej
Udalski of Warsaw University. Two other collaborations-the Probing
Lensing Anomalies NETwork (PLANET) and Microlensing Observations in
Astrophysics (MOA) -also followed the event and contributed to the
journal paper.

Gravitational microlensing occurs when a massive object in space, like
a
star or even a black hole, crosses in front of a star shining in the
background. The object's strong gravitational pull bends the light rays
from the more distant star and magnifies them like a lens. On earth,
observers see the star get brighter as the lens crosses in front of it,
and then fade as the lens gets farther away. The presence of a planet
orbiting the nearby star will modify this otherwise smooth process in a
predictable way.

The paper announcing this discovery will be published in an upcoming
issue of The Astrophysical Journal Letters and is available online at
http://arxiv.org/abs/astro-ph/0505451.

Note to editors: An image to accompany this release is online at
http://www.cfa.harvard.edu/press/pr0514image.html.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics (CfA) is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.

For more information, contact:

David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468


Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016