Washington, D.C. – After 15 years of observation and lots of
patience, the world’s premier planet-hunting team has finally found a
planetary system that reminds them of our own solar system.
At a press conference today (Thursday, June 13) at National
Aeronautics and Space Administration (NASA) headquarters, University
of California, Berkeley, astronomer Geoffrey W. Marcy and Carnegie
Institution of Washington astronomer Paul Butler announced the
discovery of a Jupiter-like planet orbiting a sun-like star at nearly
the same distance as Jupiter orbits our sun.
The press conference will be Webcast live at

“This is the first near analog to our Jupiter,” said Marcy,
professor of astronomy and director of UC Berkeley’s Center for
Integrative Planetary Science. “All other extrasolar planets
discovered up to now orbit closer to the parent star, and most of
them have had elongated, eccentric orbits. This new planet orbits as
far from its star as our own Jupiter orbits the sun.”

The star, 55 Cancri in the constellation Cancer, was already
known to have one planet, which was announced by Butler and Marcy in
1996. That planet is a gas giant slightly smaller than the mass of
Jupiter, and whips around the star in 14.6 days at a distance only
one tenth that from the Earth to the sun. Using the 93-million-mile
Earth-sun distance as a yardstick, called an astronomical unit or AU,
the newly found planet orbits at 5.5 AU, comparable to Jupiter’s 5.2
AU distance from the sun. With a mass between 3.5 and 5 times that of
Jupiter, the planet has a slightly elongated orbit that carries it
around the star in about 13 years, comparable to Jupiter’s orbital
period of 11.86 years.

“We haven’t yet found an exact solar system analog, with a
planet in a circular orbit and a mass closer to that of Jupiter,”
Butler said. “But this shows we are getting close, we are at the
point of finding planets at distances greater than 4 AU from the host
star. And we found this planet among the 107 stars we first targeted
when we started looking for planets at Lick Observatory in 1987, so I
think we will be finding more of them among the 1,200 stars we are
now monitoring.”

The planet-hunting team, funded by grants from the National
Science Foundation and NASA, announced a total of 15 new planets
today, including the smallest ever detected: a planet circling the
star HD49674 in the constellation Auriga at a distance of 0.05 AU –
one-twentieth the distance from the Earth to the sun. Its mass is
about 15 percent that of Jupiter, or nearly half that of Saturn, and
40 times the mass of the Earth. This brings the total number of known
planets outside the solar system to more than 90.

The team of astronomers passed their data on 55 Cancri along
to theoretical astronomer Greg Laughlin, assistant professor of
astronomy and astrophysics at UC Santa Cruz, who conducted dynamical
calculations that show an Earth-sized planet could survive in a
stable orbit between the two gas giants.

“We tried a hypothetical configuration of a terrestrial
planet in the habitable zone around one AU from the central star and
found it very stable,” said Laughlin, who also is associated with
Lick Observatory. “Just as the other planets in our solar system tug
on the Earth and produce a chaotic but bounded orbit, so the planets
around 55 Cancri would push and pull an Earthlike planet in a manner
that would not cause any collisions or wild orbital variations.”

For the foreseeable future, any such planet in the habitable
zone around 55 Cancri will remain speculative.

“Nevertheless, this planetary system will be the best
candidate for direct pictures when the Terrestrial Planet Finder is
launched later this decade,” said UC Berkeley astronomer Debra A.
Fischer, referring to NASA’s planned space-borne imaging telescope
designed to take pictures of Earth-sized planets.

The star 55 Cnc is 12.5 parsecs (41 light years) distant and
a middle-aged, 4-7 billion-year-old G8 star rich in heavy elements
like carbon, iron, silicon and sulfur, Fischer said. The sun is about
5 billion years old, with half that amount of heavy metals.
Laughlin speculated that the large, inner planet probably
formed farther from the parent star, where ice could form and rocks
accrete to form a solid core, and only migrated inward after it had
scooped up a shroud of gas. This inward migration is a characteristic
of giant planets in a disk of gas and dust that is typical of forming
planetary systems, he said. They create a spiral wake that actually
tugs on the planet, slowing it down and sending it spiraling inward
toward the star.

“To me, the question is why it stopped before crashing into
the star,” Laughlin said. Numerous giant extrasolar planets have been
found in very short-period orbits – 3 to 3.5 days – when, by all
rights, they should have spiraled to a flaming death.

There also may be another planet around 55 Cnc, because the
two known planets do not yet explain all the observed Doppler
wobbling. The team needs more data before they can come to a final
conclusion, but one possibility is a Saturn-mass planet orbiting
about 0.24 AU from the star, or one-quarter the Earth-sun distance.

Marcy and Butler originated a sensitive technique for
measuring the slight Doppler shift in starlight caused by a wobble in
the position of a star, a periodic shift due to a planet yanking on
the star as it orbits. From measurements over a period of years, they
are able to infer the period, its approximate mass and the size of
its orbit. Uncertainties arise because there is no way to determine
the orientation of the orbit – whether we are seeing it edge on, or
tilted to face toward us.

Discovery of a second planet orbiting 55 Cnc is the
culmination of 15 years of observations using the 3-meter telescope
at Lick Observatory, which is owned and operated by the University of
California. Four of the 13 newly found planets were discovered at the
3.9-meter Anglo-Australian Telescope in New South Wales, Australia.
In addition to the 300 stars the team monitors with the Lick
telescope, the astronomers are following another 650 with the
10-meter Keck Telescope in Hawaii and another 250 southern hemisphere
stars with the 3.9-meter AAT. Within a couple of years, they hope to
use the 6.5-meter Magellan telescopes at Las Campanas Observatory in
Chile to ramp up to 2,000 stars, all within 50 parsecs (150 light
years) of Earth.

“This will cover all the good candidates out to 50 parsecs,
so we will know where to look when we have the Terrestrial Planet
Finder and the Space Interferometry Mission, which will do the first
reconnaissance to identify Earth-like planets,” Butler said.
In addition to Marcy, Butler, Fischer and Laughlin,
collaborators on the project include Steve Vogt, professor of
astronomy and astrophysics at UC Santa Cruz; Greg Henry of the Center
of Excellence in Information Systems at Tennessee State University,
Nashville; Dimitri Pourbaix of the Institut d’Astronomie et
d’Astrophysique, Universite’ Libre de Bruxelles; Hugh Jones of the
Astrophysics Research Institute at Liverpool John Moores University
in the United Kingdom; Chris Tinney of the Anglo-Australian
Telescope; Chris McCarthy of the Department of Terrestrial Magnetism
at the Carnegie Institution of Washington; Brad Carter of the
University of Southern Queensland, Australia; and Alan Penny of the
Rutherford Appleton Laboratory in the United Kingdom.


NOTE: Paul Butler can be reached at the Carnegie Institution in
Washington: paul@dtm.ciw.edu or (202) 478-8866. Debra Fischer can be
reached at fischer@astro.berkeley.edu or (415) 643-8973, and Steven
Vogt at vogt@ucolick.org. Greg Laughlin is at (831) 459-3208 or

Animation and an artist’s concept are available at
More information on planet-finding research and future missions is
available at:


An artistic rendering of the planetary system by noted artist Lynette
Cook can be downloaded for use free of charge at
http://www.berkeley.edu/news/media/download/. Please credit Lynette