For the first time: a photograph of a planet outside the solar system * Hubble's success * The image was taken by Hubble's 'Nicomos' infrared camera
Maggie McKee, New Scientist
Is this a historical picture? Two objects, the smaller of which may be a planet. Photo: Hubble Space Telescope
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An image that NASA defines as nothing less than the history of a planet orbiting another star, taken by the Hubble Space Telescope. A "planet" 5-10 times the diameter of Jupiter orbits a white dwarf located about a hundred light years from us.
The astronomers take a bit more caution, and say that additional data is needed to be sure that it is indeed a planet and not an object in the background that was caught in the same field of view.
The confirmation will come after additional observations are made that show that the two objects are indeed moving together in space.
During the last 10 years, scientists have discovered more than 120 planets outside the solar system, but all of them were found through indirect processes rather than direct observation.
Glowing ball
The new image of Hubble was taken by John Debes, a graduate student at Pennsylvania State University, as part of a project to search for planets orbiting other suns. The big problem in observing such planets is not sensitivity but contrast." Dance told the BBC. "The presence of a bright mother star makes the planet relatively dim and difficult to observe.
That's why Debs and his colleagues looked for planets around dim white dwarfs - stars at the end of their lives that have shrunk into a glowing ball the size of Earth. "We studied seven white dwarfs and around three of them we saw what might be planets. In one of them, the planet is several times larger than Jupiter.” said.
The as-yet-unnamed world is about the same distance from its sun as Neptune is from our sun.
The planet began its life several billion years ago at a much closer distance to its parent star. The parent star used to be close and must have been much more massive and brighter than our Sun. At the end of his life he must have spread and destroyed all the planets close to him. Only the more distant ones could survive, and as the star lost mass, their orbits expanded, due to the planet's reduced gravity.
Debs remains cautious about the bone until it is established with certainty that it is related to the white dwarf. "If this is indeed a planet and not a background star in the same line of sight, we should see it moving with the star across the sky within a few months."
Debs plans follow-up observations with the Hubble Space Telescope and ground-based telescopes.
A new type of hot, fast-moving planet has been discovered
Astronomers have discovered two hot and fast planets outside the solar system. Astronomers say the hot gas giants may represent a new type of planet. This is what the New Scientist magazine says.
The planets were discovered during their transit in front of their star, a transit that causes the brightness of the star to weaken. These two planets are added to two other planets, which were previously seen transiting in front of their star.
All but one of the 120 extrasolar planets (planets outside the solar system) discovered so far complete orbits around their star in about three Earth days or more, but the two new planets, which are the size of Jupiter, move at tremendous speed and complete orbits in less than two days.
"They give the impression of a completely new type, and it is not yet clear whether they were formed in a different way," says Guillermo Torres, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, United States, who confirmed the discovery of one of the planets.
Current theory holds that planets such as Jupiter can form at a distance from their sun that is not less than the distance between Earth and the sun. However, in such a case the gravitational interactions with the gas in the environment or with other planets may push them inward towards the star.
Apparently, most of the extrasolar planets went through this migration and became a kind of "hot Jupiter" state. The newly discovered planets, which are estimated to be extremely rare, have been nicknamed "boiling Jupiter". They are at a distance from their sun that is one fiftieth of the distance between the Earth and the sun. The previous closest planet was twice as far away.
It's possible that the new planets' proximity to their sun causes them to lose some of their mass to their star, Torres says. "Another interesting thing is that they are so close to their star and so hot, and the radiation from their star can change their structure."
The gas giants were discovered by a team led by François Bauchy of the Astrophysics Laboratory in Marseille, France. The team used an 8.2 meter dish spectrograph at the Very Large Telescope (VLT) in Paranal, Chile. The two planets were discovered among a list of 41 dimming stars selected by astronomers from the OGLE study at Las Campanes Observatory in Chile. OGLE has been scouring the sky since 2000 for stars whose light periodically dims because planets are believed to be present in such systems.
The dimming effect usually originates from other stars or brown dwarfs, which pass in front of their star from Earth's perspective. A direct transit of a planet between Earth and its star is a rare event.
The two new planets, called 113-TR-OGLE and 132-TR-OGLE, are 6000 and 1200 light years from Earth respectively, in the southern constellation Carina. 113-TR-OGLE is about 35 percent more massive than Jupiter, and it completes an orbit around its star every 1.43 days. The Jupiter-sized 132-TR-OGLE completes one orbit around its star every 1.69 days.
The extrasolar planet detection method allows astronomers to determine the mass of the planets by measuring the motion of the stars toward the planets.
Most of the extrasolar planets were discovered with the help of the gravitational pull they exert on their star, which causes the star to "dance". However, this method cannot be used to estimate the mass of the planet.
Torres told New Scientist that the discovery of the two planets confirms the fact, "that the method of transiting a planet in front of its star is particularly effective for detecting Jupiter-sized planets."
In 2007, NASA will launch the Kepler mission, which will search for transits of Earth-sized planets in front of their star.
The new discoveries will be published in the next issue of the magazine Astronomy and Astrophysics.
Translation: Dikla Oren
The article in New Scientist
Know planets outside the solar system
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