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Contact: Jane Platt
FOR IMMEDIATE RELEASEApril 21, 1998
NASA ASTRONOMERS FIND PLANET CONSTRUCTION ZONE AROUND NEARBY STAR
NASA astronomers using the new Keck II
telescope in Hawaii have discovered what appears to be the clearest evidence
yet of a budding solar system around a nearby star.
Scientists released an image of the
probable site of planet formation around a star known as HR 4796, about 220
light-years from Earth in the constellation Centaurus. The image, taken with
a sensitive infrared camera developed at NASA's Jet Propulsion Laboratory,
shows a swirling disc of dust around the star. Within the disc is a telltale
empty region that may have been swept clean when material was pulled into
newly formed planetary bodies, the scientists said.
"This may be what our solar system
looked like at the end of its main planetary formation phase," said Dr.
Michael Werner of JPL, who co-discovered the region, along with Drs. David
Koerner and Michael Ressler, also of JPL, and Dana Backman of Franklin and
Marshall College, Lancaster, PA. "Comets may be forming right now in the
disc's outer portion from remaining debris."
The discovery was made on March 16 from
the giant 10-meter (33-foot) Keck II telescope atop Mauna Kea, Hawaii. Keck
II and its twin, Keck I, are the world's largest optical and infrared
telescopes. Attached to the Keck II for this observation was the
mid-infrared camera, developed by Ressler at JPL and designed to measure
heat radiation.
The four scientists reported their
discovery in a submission to Astrophysical Journal Letters. The disc was
discovered independently and contemporaneously at the Cerro Tololo
Observatory in Chile by another team of scientists, led by Ray Jayawardhana
of the Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, and Dr.
Charles Telesco of the University of Florida, Gainesville.
Koerner of JPL said the finding
represents a "missing link" in the study of how planetary systems are born
and evolve. "In a sense, we've already peeked into the stellar family album
and seen baby pictures and middle-aged photos," Koerner said. "With HR 4796,
we're seeing a picture of a young adult star starting its own family of
planets. This is the link between discs around very young stars and discs
around mature stars, many with planets already orbiting them."
"This is the first infrared image where
an entire inner planetary disc is clearly visible," Werner said. "The
planet- forming disc around the star Beta Pictoris was discovered in 1983 by
the Infrared Astronomical Satellite (IRAS), and also later imaged with the
Hubble Space Telescope, but glaring light from the star partially obscured
its disc."
The apparent diameter of the dust disc
around HR 4796 is about 200 astronomical units (one astronomical unit is the
distance from Earth to the Sun). The diameter of the cleared inner region is
about 100 astronomical units, slightly larger than our own solar system.
HR 4796 was originally identified as an
interesting object for further study by Dr. Michael Jura, an astronomy
professor at the University of California, Los Angeles. The star, HR 4796,
is about 10 million years old and is difficult to see in the continental
United States, but is visible to telescopes in Hawaii and the southern
hemisphere.
The discovery of the HR 4796 disc was
made in just one hour of observing time at Keck, but the JPL team plans to
return to Hawaii in June for further studies. They hope to learn more about
the structure, composition and size of this disc, and to determine how discs
around stars in our galaxy produce planets. They plan to study several other
stars as well, including Vega, which was featured prominently in the movie,
"Contact."
The Harvard/Florida research team that
also found the HR 4796 disc included Drs. Lee Hartmann and Giovanni Fazio of
Harvard-Smithsonian Center for Astrophysics, and Scott Fisher and Dr. Robert
Pina of the University of Florida.
JPL's use of the Keck telescope is
supported by NASA's Origins program, a series of missions to study the
formation of galaxies, stars, planets and life, and to search for Earth-like
planets around other stars that might have the right conditions for life.
The W. M. Keck Observatory is owned and
operated by the California Association for Research in Astronomy, a joint
venture between the University of California, the California Institute of
Technology and NASA. Use of the Keck Observatory for Origins research is
managed by JPL for NASA's Office of Space Science, Washington, DC. JPL is a
division of Caltech.
The research of both teams was
supported in large part by the NASA Origins Program, with additional support
to the Harvard/Florida team from the National Science Foundation, the
National Optical Astronomy Observatories, and the Smithsonian Institution;
and with additional NASA support for the Caltech/JPL-Franklin & Marshall
team, including use of the Keck Observatory.