An odd planet the size of Neptune, made mostly of hot, solid water,
was discovered last year and offers evidence that other planets may be
covered with oceans, and European astronomers reported with more
information last Wednesday. Called GJ436b, the planet orbits quickly
around a cool, red star just 30 light-years away, the team at the
Geneva Observatory said. "It's not a very welcoming planet," Frederic
Pont, an astronomer who helped make the discovery, said in a telephone
interview. 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'. "The water is frozen by the pressure but it's hot. 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,"
Pont said.

The planet is also likely blanketed by hydrogen,the researchers said -
conditions hardly conducive to life. But if there is water, there
could be water on other planets in other solar systems
and thus perhaps life as we know it, perhaps not.

"It shows there could be many ocean planets," Pont said.Using a Swiss-
based telescope, the team determined the size of the planet by
watching it pass in front of its star. The rest is
guesswork, but it is easy guesswork, Pont said."When it passes in
front of the star it is like a mini eclipse,"Pont said. 'Smaller stars
are cooler and redder' "The amount of light that it hides is
proportional to its size,"he said. And the size says a lot.
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.And many appear to be gas giants
like Jupiter. This one appears to be smaller, but not small enough to
have a rocky
centre as the Earth does."From the size and the mass we get the
density," Pont said. And the density of GJ436b suggests it is made of
water.

"No one can be absolutely sure that it's water, but with this kind of
density and if you take the matterials that usually make a planet, it
is very typical of water planets," Pont said.

The researchers wrote in their report:
"The mass and radius that we measure for GJ436b indicate that it is
mainly
composed of water ice. It is an 'ice giant' planet like Uranus and
Neptune
rather than a small-mass gas giant."
It is very close to its star, the M-dwarf star GJ436. "It's a small
star, 100 times less bright than the sun," Pont said. It is about half
the sun's mass."Smaller stars are cooler and redder," he added.That is
why the water can persist, albeit in a hot and solid state. The
astronomers estimate its 250 degrees Celsius."It is by far the
closest, smallest and least massive
transiting planet detected so far," the researchers, who included a
team in Tel Aviv, Israel, wrote in their report published in the
journal Astronomy & Astrophysics.

The star is relatively close in astronomical terms, about 33 light-
years away. A light-year is the distance light travels in a year at
300 000km per second, or close to 10 trillion kilometres.
Just last month members of the same team said they had found the most
Earth-like planet yet outside our solar system, with balmy
temperatures and orbiting a red dwarf star called Gliese 581.

Darrell Lakin
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Smithfield, VA 23430