A long (149 years ago) time ago in a galaxy not really that far away...

(be sure to check out the animations!!!!)

N E W S R E L E A S E

Embargoed until 10:00 AM PDT, Wednesday, July 13, 2005

First Planet Under Three Suns Is Discovered

PASADENA, Calif.--An extrasolar planet under three suns has been
discovered in the constellation Cygnus by a planetary scientist at
the California Institute of Technology using the 10-meter Keck I
telescope in Hawaii. The planet is slightly larger than Jupiter and,
given that it has to contend with the gravitational pull of three
bodies, promises to seriously challenge our current understanding of
how planets are formed.

In the July 14 issue of Nature, Maciej Konacki, a senior postdoctoral
scholar in planetary science at Caltech, reports on the discovery of
the Jupiter-class planet orbiting the main star of the
close-triple-star system known as HD 188753. The three stars are
about 149 light-years from Earth and are about as close to one
another as the distance between the sun and Saturn.

In other words, a viewer there would see three bright suns in the
sky. In fact, the sun that the planet orbits would be a very large
object in the sky indeed, given that the planet's "year" is only
three and a half days long. And it would be yellow, because the main
star of HD 188753 is very similar to our own sun. The larger of the
other two suns would be orange, and the smaller red.

Konacki refers to the new type of planet as "Tatooine planets,"
because of the similarity to Luke Skywalker's view of his home
planet's sky in the first Star Wars movie.

"The environment in which this planet exists is quite spectacular,"
says Konacki. "With three suns, the sky view must be out of this
world-literally and figuratively."

However, Konacki adds that the fact that a planet can even exist in a
multiple-star system is amazing in itself. Binary and multiple stars
are quite common in the solar neigborhood, and in fact outnumber
single stars by some 20 percent.

Researchers have found most of the extrasolar planets discovered so
far by using a precision velocity technique that is easier to employ
on studies of single stars. Experts generally avoided close-binary
and close-multiple stars because the existing planet detection
techniques fail for such complicated systems, and also because
theories of solar-system formation suggested that planets were very
unlikely to form in such environments.

Konacki's breakthrough was made possible by his development of a
novel method that allows him to precisely measure velocities of all
members of close-binary and close-multiple-star systems. He used the
technique for a search for extrasolar planets in such systems with
the Keck I telescope. The planet in the HD 188753 system is the first
one from this survey.

"If we believe that the same basic processes lead to the formation of
planets around single stars and components of multiple stellar
systems, then such processes should be equally feasible, regardless
of the presence of stellar companions," Konacki says. "Planets from
complicated stellar systems will put our theories of planet formation
to a strict test."

Scientists in 1995 discovered the first "hot Jupiter"-in other words,
an extrasolar gas-giant planet with an orbital period of three to
nine days. Today, more than 20 such planets are known to orbit other
stars. These planets are believed to form in a disk of gas and
condensed matter at or beyond three astronomical units (three times
the 93-million-mile distance between the sun and Earth).

A sufficient amount of solid material exists at three astronomical
units to produce a core capable of capturing enough gas to form a
giant planet. After formation, these planets are believed to migrate
inward to their present very close orbits.

If the parent star is orbited by a close stellar companion, then its
gravitational pull can significantly truncate a protoplanetary disk
around the main star. In the case of HD 188753, the two stellar
companions would truncate the disk around the main star to a radius
of only 1.3 astronomical units, leaving no space for a planet to form.

"How that planet formed in such a complicated setting is very
puzzling. I believe there is yet much to be learned about how giant
planets are formed," says Konacki.

[Note to editors: Two embargoed animations of the three-sun
system-one in low resolution and the other in high resolution-are now
available at the following links:

A still image will be available on Monday by calling the number below]

Contact: Robert Tindol
(626) 395-3631
tindol@caltech.edu