JHU Device Helps Locate Brown Dwarf Emil Venere ------------------------------------ Homewood News and Information Using an image-sharpening device designed and built at Hopkins, astronomers at Hopkins and the California Institute of Technology have made the first confirmed discovery of something resembling a planet orbiting a star. The astronomers--relying on the adaptive optics coronagraph mounted on a telescope at Mount Palomar in California--found and photographed a brown dwarf, a cosmic object too massive to be a planet but too small and cool to shine like a star, in orbit around a star 19 light-years from Earth in the constellation Lepus. The discovery marks the first time astronomers can be certain that they have identified a brown dwarf. Details of the observation, confirmed by the Hubble Space Telescope on Nov. 17 at the Palomar Observatory in southern California, were published in the Nov. 30 issue of the British journal Nature. Brown dwarfs are thought to be failed stars; they did not start out with enough mass to generate the high temperatures needed to bring about nuclear fusion, which makes stars shine. Astronomers have long been able to observe stars orbiting other stars, in so-called binary star systems, but the Caltech/Hopkins discovery marks the first time that a more planet-like object has been observed in orbit around a star. The team of astronomers deduce that the object is about 20 times more massive than Jupiter, even though it probably is about the same size as Jupiter. It orbits a red-colored star called Gliese 229, some 112 trillion miles from Earth. "This is clearly a brown dwarf," said Samuel Durrance, a Hopkins astrophysicist who conceived the idea for the adaptive optics coronagraph, which was needed to make the crisp images. "One difference between planets and brown dwarfs lies in how they formed." The brown dwarf, named GL 229B, is probably similar in many respects to the large gaseous planets in our solar system, he said. The astronomers suspect that the brown dwarf developed during the normal star-formation process as one of two members of a binary system. The brown dwarf did not acquire enough mass to become a star. Astronomers cannot yet rule out the possibility that GL 229B formed as a super-size planet. All of the planets in our solar system, including the large gaseous planets like Jupiter and Saturn, are believed to have formed from material in a primeval disk of dust around our newborn sun. They did not start out as potential stars. The discovery of GL 229B comes three years into a long-term project to search for "low-mass" companions of stars near Earth. The brown dwarf was first observed in October 1994 using the adaptive optics device and a 60-inch reflecting telescope at Mount Palomar, said David Golimowski, an associate research scientist in the Department of Physics and Astronomy. Golimowski, who has been involved in designing and building the coronagraph since its inception, was one of the astronomers who made the historic observation. It took another year to confirm that the object was actually an orbiting companion of the star. Although the astronomers do not know the brown dwarf's orbit, they estimate that its distance from the star is at least the same as Pluto's from the sun, about 4 billion miles. "I don't want to say this is the discovery of a lifetime because I'm hoping that the rest of my astronomical career will be filled with things like this," said the 32-year-old Golimowski. "This has been sort of the holy grail for a lot of people."
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