Speculate about the new super-earth recently detected

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

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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."



--
"And he did bring them. It took a number of years, but one by one he
brought them here. Except for his father, that old man died where he was
born." -+ "Elia Kazan, "America, America"