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05-17-2007, 08:17 AM
By Reuters and Los Angeles Times
WASHINGTON — A recently discovered planet is the size of Neptune and made up mostly of hot, solid water, European astronomers reported Wednesday.
The planet, called GJ 436b, orbits quickly around a dim, red star about 33 light-years away, the team at the Geneva Observatory said.
"It's not a very welcoming planet," said Frederic Pont, an astronomer who helped make the discovery. The planet is hot because it is near its star and under high pressure because of its mass.
"The water is 'frozen' by the pressure, but it's hot," Pont said. "It's a bit strange — we are used to water changing conditions because of temperature, but in fact water can also be solidified by pressure."
The planet was discovered in 2004 by a team of U.S. scientists who observed it only indirectly.
"All we could tell is that it was there and about how much mass was there," said astronomer Jason Wright of the University of California, Berkeley, part of the original team. "Now we know much more about the planet than we did before. It is a very exciting discovery that they made."
Using a Swiss-based telescope, the University of Geneva team determined the size of the planet by watching it pass in front of its star. The rest is guesswork, Pont said.
"When it passes in front of the star, it is like a mini eclipse," he said. "The amount of light that it hides is proportional to its size."
Astronomers have found about 200 so-called extrasolar planets orbiting stars other than our sun. Many are detected by indirect measurements such as tiny variations in the wobble of a star caused by the gravitational tug of a planet.
Many of the extrasolar planets appear to be gas giants like Jupiter. This one appears to be smaller, but not small enough to be rocky, as Earth is.
Key to the conclusion that GJ 436 b could be an ocean planet was determining its density. Researchers first determined the size of the planet by watching it pass in front of its star, causing a kind of mini-eclipse.
"From the size and the mass we get the density," Pont said.
"It is an 'ice giant' planet like Uranus and Neptune rather than a small-mass gas giant or a very heavy 'super-Earth,' the researchers wrote in their report, published in the journal Astronomy & Astrophysics.
The planet orbits the M-dwarf star GJ 436, about half the mass of the sun but a hundred times dimmer. The planet is quite near its star, orbiting it every three days. So even though the star is relatively cool, the planet's surface is hot, estimated at about 476 degrees Fahrenheit.
The scientists said the planet could have an atmosphere of hydrogen and helium. Combined with the scorching heat, that would make the planet hostile to life, at least as we know it. But if the planet is covered in water, it makes the possibility of finding other planets with water in more hospitable orbital zones more likely.
source: http://seattletimes.nwsource.com/html/nationworld/2003710356_planet17.html
WASHINGTON — A recently discovered planet is the size of Neptune and made up mostly of hot, solid water, European astronomers reported Wednesday.
The planet, called GJ 436b, orbits quickly around a dim, red star about 33 light-years away, the team at the Geneva Observatory said.
"It's not a very welcoming planet," said Frederic Pont, an astronomer who helped make the discovery. The planet is hot because it is near its star and under high pressure because of its mass.
"The water is 'frozen' by the pressure, but it's hot," Pont said. "It's a bit strange — we are used to water changing conditions because of temperature, but in fact water can also be solidified by pressure."
The planet was discovered in 2004 by a team of U.S. scientists who observed it only indirectly.
"All we could tell is that it was there and about how much mass was there," said astronomer Jason Wright of the University of California, Berkeley, part of the original team. "Now we know much more about the planet than we did before. It is a very exciting discovery that they made."
Using a Swiss-based telescope, the University of Geneva team determined the size of the planet by watching it pass in front of its star. The rest is guesswork, Pont said.
"When it passes in front of the star, it is like a mini eclipse," he said. "The amount of light that it hides is proportional to its size."
Astronomers have found about 200 so-called extrasolar planets orbiting stars other than our sun. Many are detected by indirect measurements such as tiny variations in the wobble of a star caused by the gravitational tug of a planet.
Many of the extrasolar planets appear to be gas giants like Jupiter. This one appears to be smaller, but not small enough to be rocky, as Earth is.
Key to the conclusion that GJ 436 b could be an ocean planet was determining its density. Researchers first determined the size of the planet by watching it pass in front of its star, causing a kind of mini-eclipse.
"From the size and the mass we get the density," Pont said.
"It is an 'ice giant' planet like Uranus and Neptune rather than a small-mass gas giant or a very heavy 'super-Earth,' the researchers wrote in their report, published in the journal Astronomy & Astrophysics.
The planet orbits the M-dwarf star GJ 436, about half the mass of the sun but a hundred times dimmer. The planet is quite near its star, orbiting it every three days. So even though the star is relatively cool, the planet's surface is hot, estimated at about 476 degrees Fahrenheit.
The scientists said the planet could have an atmosphere of hydrogen and helium. Combined with the scorching heat, that would make the planet hostile to life, at least as we know it. But if the planet is covered in water, it makes the possibility of finding other planets with water in more hospitable orbital zones more likely.
source: http://seattletimes.nwsource.com/html/nationworld/2003710356_planet17.html