http://www.cfa.harvard.edu/press/2009/pr200905.html

Harvard-Smithsonian Center for Astrophysics Press Release
Release No.: 2009-05
For Release: Friday, January 16, 2009

Transit Search Finds Super-Neptune

Cambridge, MA - Astronomers at the Harvard-Smithsonian Center for
Astrophysics have discovered a planet somewhat larger and more massive
than Neptune orbiting a star 120 light-years from Earth. While Neptune
has a diameter 3.8 times that of Earth and a mass 17 times Earth's,
the
new world (named HAT-P-11b) is 4.7 times the size of Earth and has 25
Earth masses.

HAT-P-11b was discovered because it passes directly in front of
(transits) its parent star, thereby blocking about 0.4 percent of the
star's light. This periodic dimming was detected by a network of
small,
automated telescopes known as "HATNet," which is operated by the
Center
in Arizona and Hawaii. HAT-P-11b is the 11th extrasolar planet found
by
HATNet, and the smallest yet discovered by any of the several transit
search projects underway around the world.

Transit detections are particularly useful because the amount of
dimming
tells the astronomers how big the planet must be. By combining transit
data with measurements of the star's "wobble" (radial velocity) made
by
large telescopes like Keck, astronomers can determine the mass of the
planet.

A number of Neptune-like planets have been found recently by radial
velocity searches, but HAT-P-11b is only the second Neptune-like
planet
found to transit its star, thus permitting the precise determination
of
its mass and radius.

The newfound world orbits very close to its star, revolving once every
4.88 days. As a result, it is baked to a temperature of around 1100
degrees F. The star itself is about three-fourths the size of our Sun
and somewhat cooler.

There are signs of a second planet in the HAT-P-11 system, but more
radial velocity data are needed to confirm that and determine its
properties.

Another team has located one other transiting super-Neptune, known as
GJ436b, around a different star. It was discovered by a radial
velocity
search and later found to have transits.

"Having two such objects to compare helps astronomers to test theories
of planetary structure and formation," said Harvard astronomer Gaspar
Bakos, who led the discovery team.

HAT-P-11 is in the constellation Cygnus, which puts in it the field of
view of NASA's upcoming Kepler spacecraft. Kepler will search for
extrasolar planets using the same transit technique pioneered by
ground-based telescopes. This mission potentially could detect the
first
Earth-like world orbiting a distant star. "In addition, however, we
expect Kepler to measure the detailed properties of HAT-P-11 with the
extraordinary precision possible only from space," said Robert Noyes,
another member of the discovery team.

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 A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar{at}cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam{at}cfa.harvard.edu
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