[posted and mailed]

The rec.arts.sf.* newsgroup this belongs in is rec.arts.sf.science, to
which I have now redirected it.

"Bill Bonde ( ``Soli Deo Gloria'' )" wrote in
:

http://www.space.com/scienceastronom...th_040825.html

#begin quote
In a discovery that has left one expert stunned, European astronomers
have found one of the smallest planets known outside our solar system,
a world about 14 times the mass of our own around a star much like the
Sun.

It could be a rocky planet with a thin atmosphere, a sort of "super
Earth," the researchers said today.

But this is no typical Earth. It completes its tight orbit in less
than 10 days, compared to the 365 required for our year. Its daytime
face would be scorched.

The planet's surface conditions aren't known, said Portuguese
researcher Nuno Santos, who led the discovery. "However, we can expect
it to be quite hot, given the proximity to the star."

Hot as in around 1,160 degrees Fahrenheit (900 Kelvin), Santos told
SPACE.com.

Still, the discovery is a significant advance in technology: No planet
so small has ever been detected around a normal star. And the finding
reveals a solar system more similar to our own than anything found so
far.

Terrestrial in nature

The star is like our Sun and just 50 light-years away. A light-year is
the distance light travels in a year, about 6 trillion miles (10
trillion kilometers). Most of the known extrasolar planets are
hundreds or thousands of light-years distant.

The star, mu Arae, is visible under dark skies from the Southern
Hemisphere. It harbors two other planets. One is Jupiter-sized and
takes 650 days to make its annual trip around the star. The other
planet, whose existence was confirmed with the help of the new
observations, is farther out.

The three-planet setup, with one being rocky, is unique.

"It's much closer to our solar system than anything we've found so
far," said Alan Boss, a planet-formation theorist at the Carnegie
Institution in Washington.

"This really is an exciting discovery," said Boss, who was not
involved in the work. "I'm still somewhat stunned they have such good
data."

The discovery was made with a European Southern Observatory telescope
at La Silla, Chile, working at the verge of what's possible to detect.
Most of the more than 120 planets found beyond our solar system are
gaseous worlds as big or larger than Jupiter, mostly in tight orbits
that would not permit a rocky planet to survive.

A handful of planets smaller than Saturn have been found, but none
anywhere near as small as the one announced today. And a trio of
roughly Earth-sized planets was found in 2002 to orbit a dense stellar
corpse known as a neutron star. They are oddballs, however, circling
rapidly around a dark star that would not support life. Some planet
hunters don't consider these three to be as important as planets
around normal stars.

At 14 times the mass of Earth, the newfound planet -- circling a star
similar in size and brightness to our Sun -- is about as heavy as
Uranus, a world of gas and ice and the smallest giant planet in our
solar system. Theorists say 14 Earth-masses is roughly the upper limit
for a planet to possibly remain rocky, however. And because this
planet is so close to its host star, it likely had a much different
formation history than Uranus.

In our solar system, the four innermost planets are all rocky.

Rock and air

The leading theory of planet formation has the gas giants forming from
a rocky core, a process in which the core develops over time, then
reaches a tipping point when gravity can rapidly collect a huge
envelope of gas. This theory suggests the newfound planet never
reached that critical mass, said Santos, of the Centro de Astronomia e
Astrofisica da Universidade de Lisboa, Portugal.

"Otherwise the planet would have become much more massive," Santos
said via e-mail.

"This object is therefore likely to be a planet with a rocky core
surrounded by a small gaseous envelope and would therefore qualify as
a super-Earth," the European team said in a statement.

In a telephone interview, Boss of the Carnegie Institution said the
European's analysis of the data represents a "reasonable argument." He
said the planet had to form inside the orbit of the larger planet in
the system, which orbits the star about twice as far as Earth is from
the Sun. Boss also points out that Earth is about 18 times as massive
as Mercury, so even in our solar system there is a range of
possibilities for rocky planets.

Finally, Boss said, the star mu Arae has a higher metal content than
the Sun, and theory says a planet forming close to such a star can be
expected to gather more mass. It's all about how much building
material is available, he said.

There are no conventional pictures of the object, as it was detected
by noting its gravitational effect on the star. The search project
leading to the discovery is led by Michel Mayor of the Geneva
Observatory in Switzerland.

While researchers do not know the full range of conditions under which
life can survive, the newly discovered world, with its hot surface, is
not the sort of place biologists would expect to find life as we know
it.

Santos said life on the large world is not likely. But, he added, "one
never knows."






--
Dan Goodman
Journal http://dsgood.blogspot.com or
http://www.livejournal.com/users/dsgood/ Whatever you wish for me, may
you have twice as much.