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Planetary discovery NASA NEWS RELEASE Posted: July 1, 2005 NASA researchers recently discovered the largest solid core ever found in an extrasolar planet, and their discovery confirms a planet formation theory.
When a consortium of American, Japanese and Chilean astronomers first looked at this planet, they expected one similar to Jupiter. "None of our models predicted that nature could make a planet like the one we are studying," said Bun'ei Sato, consortium member and postdoctoral fellow at Okayama Astrophysical Observatory, Japan. Scientists have rarely had opportunities like this to collect such solid evidence about planet formation. More than 150 extrasolar planets have been discovered by observing changes in the speed of a star, as it moves toward and away from Earth. The changes in speed are caused by the gravitational pull of planets. This planet also passes in front of its star and dims the starlight. "When that happens, we are able to calculate the physical size of the planet, whether it has a solid core, and even what its atmosphere is like," said Debra Fischer. She is consortium team leader and professor of astronomy at San Francisco State University, Calif. The planet, orbiting the sun-like star HD 149026, is roughly equal in mass to Saturn, but it is significantly smaller in diameter. It takes just 2.87 days to circle its star, and the upper atmosphere temperature is approximately 2,000 degrees Fahrenheit. Modeling of the planet's structure shows it has a solid core approximately 70 times Earth's mass. This is the first observational evidence that proves the "core accretion" theory about how planets are formed. Scientists have two competing but viable theories about planet formation. In the "gravitational instability" theory, planets form during a rapid collapse of a dense cloud. With the "core accretion" theory, planets start as small rock-ice cores that grow as they gravitationally acquire additional mass. Scientists believe the large, rocky core of this planet could not have formed by cloud collapse. They think it must have grown a core first, and then acquired gas. "This is a confirmation of the core accretion theory for planet formation and evidence that planets of this kind should exist in abundance," said Greg Henry, an astronomer at Tennessee State University, Nashville. He detected the dimming of the star by the planet with his robotic telescopes at Fairborn Observatory in Mount Hopkins, Arizona. Support for this research came from NASA, the National Astronomical Observatory of Japan and the National Science Foundation. A paper about this discovery was accepted for publication in the Astrophysical Journal. |
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As excitement builds for the first space shuttle launch in over two years, this comprehensive video selection captures the major pre-flight events for Discovery and her seven astronauts.
Administrator Mike Griffin is the sole witness testifying before the House Science Committee in this hearing on the future of NASA. (2hr 01min 09sec file)
One day before beginning the space shuttle Flight Readiness Review, Administrator Mike Griffin gives a televised address to agency workers and answers questions. (26min 09sec file)
The Stafford-Covey Task Group holds a news conference from NASA Headquarters following the panel's final public hearing on the space shuttle program. (55min 58sec file)
The 18th Progress resupply ship launched to the International Space Station is guided to docking with the Zvezda service module's aft port via manual control from commander Sergei Krikalev. A problem thwarted plans for an automated linkup.
The House Science Committee, Subcommittee on Space and Aeronautics, begins its hearing on the International Space Station. (29min 59sec file)
House members question Expedition 11 crew member John Phillips living on the International Space Station. (16min 33sec file)
The hearing continues with questioning by House members of former station astronauts Peggy Whitson and Mike Fincke. (31min 33sec file)