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 (JPL), Pasadena, CA, shows a swirling disk of dust around the star. Within the disk 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 disk's outer portion from remaining debris."
The discovery was made on March 16 from the giant 33-foot (10-meter) 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 The Astrophysical Journal Letters. The disk 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 (CfA), 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 disks around very young stars and disks around mature stars, many with planets already orbiting them."
"This is the first infrared image where an entire inner planetary disk is clearly visible," Werner said. "The planet- forming disk 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 disk."
The apparent diameter of the dust disk 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 disk 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 disk, and to determine how disks 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 disk 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, California Institute of Technology (Caltech), Pasadena, CA, 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 CfA- 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.
- end - The Keck II image of HR 4796 and information on the MIRLIN camera are available on the World Wide Web at: http://cougar.jpl.nasa.gov/mirlin.html.
A false-color image of the HR 4796A disk is available at: http://www.astro.ufl.edu/news/
Information on the Keck Observatory is available at: http://www2.keck.hawaii.edu:3636