Descubierto planeta rocoso de 6 masas terrestres: «En 1998, se descubría un planeta extrasolar en la estrella Gliese 876, una estrella de tipo solar que está a tan solo 15 años luz de nosotros, en la constelación de Acuario. La estrella tiene un tercio de la masa del Sol y»

Más descubrimientos... copio una nota de prensa calentita calentita. Un nuevo exoplaneta, esta vez de 7,5 veces la masa de la Tierra...

Astronomers Announce the Most Earth-Like Planet Yet Found Outside the Solar
System

EMBARGOED FOR 1:00 P.M. EDT, MONDAY, JUNE 13, 2005

Arlington, Va. Taking a major step forward in the search for Earth-like
planets beyond our own solar system, a team of astronomers has announced
the discovery of the smallest extrasolar planet yet detected. About
seven-and-a-half times as massive as Earth, with about twice the radius, it
may be the first rocky planet ever found orbiting a normal star not much
different from our Sun.

All of the nearly 150 other extrasolar planets discovered to date around
normal stars have been larger than Uranus, an ice-giant about 15 times the
mass of the Earth.
"We keep pushing the limits of what we can detect, and we're getting closer
and closer to finding Earths," said team member Steven Vogt, a professor of
astronomy and astrophysics at the University of California, Santa Cruz.

"Today's results are an important step toward answering one of the most
profound questions that mankind can ask: Are we alone in the universe?"
said Michael Turner, head of the Mathematical and Physical Sciences
Directorate at the National Science Foundation, which provided partial
funding for the research.

The newly-discovered "super-Earth" orbits the star Gliese 876, located just
15 light years away in the direction of the constellation Aquarius. This
star also possesses two larger, Jupiter-size planets. The new planet whips
around the star in a mere two days, and is so close to the star's surface
that its temperature probably tops 400 to 750 degrees Fahrenheit (200 to
400 degrees Celsius)oven-like temperatures far too hot for life as we know
it.

Nevertheless, the ability to detect the tiny wobble that the planet induces
in the star gives astronomers confidence that they will be able to detect
even smaller rocky planets in orbits more hospitable to life.

"This is the smallest extrasolar planet yet detected and the first of a new
class of rocky terrestrial planets," said team member Paul Butler of the
Carnegie Institution of Washington. "It's like Earth's bigger cousin."

The team measures a minimum mass for the planet of 5.9 Earth masses,
orbiting Gliese 876 with a period of 1.94 days at a distance of 0.021
astronomical units (AU), or 2 million miles.

Though the team has no direct proof that the planet is rocky, its low mass
precludes it from retaining gas like Jupiter. Three other purported rocky
planets have been reported, but they orbit a pulsar, the flashing corpse of
an exploded star.

"This planet answers an ancient question," said team leader Geoffrey Marcy,
professor of astronomy at the University of California, Berkeley. "Over
2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about
whether there were other Earth-like planets. Now, for the first time, we
have evidence for a rocky planet around a normal star."

Marcy, Butler, theoretical astronomer Jack Lissauer of NASA/Ames Research
Center, and post-doctoral researcher Eugenio J. Rivera of the University of
California Observatories/Lick Observatory at UC Santa Cruz presented their
findings today (Monday, June 13) during a press conference at NSF in
Arlington, Va.

Their research, conducted at the Keck Observatory in Hawaii, was supported
by NSF, the National Aeronautics and Space Administration, the University
of California and the Carnegie Institution of Washington.

A paper detailing the results has been submitted to The Astrophysical
Journal. Coauthors on the paper are Steven Vogt and Gregory Laughlin of the
Lick Observatory at the University of California, Santa Cruz; Debra Fischer
of San Francisco State University; and Timothy M. Brown of NSF's National
Center for Atmospheric Research in Boulder, Colo.

Gliese 876 (or GJ 876) is a small, red star known as an M dwarf the most
common type of star in the galaxy. It is located in the constellation
Aquarius, and, at about one-third the mass of the sun, is the smallest star
around which planets have been discovered. Butler and Marcy detected the
first planet there in 1998; it proved to be a gas giant about twice the
mass of Jupiter. Then, in 2001, they reported a second planet, another gas
giant about half the mass of Jupiter. The two are in resonant orbits, the
outer planet taking 60 days to orbit the star, twice the period of the
inner giant planet.

Lissauer and Rivera have been analyzing Keck data on the Gliese 876 system
in order to model the unusual motions of the two known planets, and three
years ago got an inkling that there might be a smaller, third planet
orbiting the star. In fact, if they hadn't taken account of the resonant
interaction between the two known planets, they never would have seen the
third planet.

"We had a model for the two planets interacting with one another, but when
we looked at the difference between the two-planet model and the actual
data, we found a signature that could be interpreted as a third planet,"
Lissauer said.

A three-planet model consistently gave a better fit to the data, added
Rivera. "But because the signal from this third planet was not very strong,
we were very cautious about announcing a new planet until we had more
data," he said.

Recent improvements to the Keck Telescope's high-resolution spectrometer
(HIRES) provided crucial new data. Vogt, who designed and built HIRES,
worked with the technical staff in the UC Observatories/Lick Observatory
Laboratories at UC Santa Cruz to upgrade the spectrometer's CCD (charge
coupled device) detectors last August.
"It is the higher precision data from the upgraded HIRES that gives us
confidence in this result," Butler said.

The team now has convincing data for the planet orbiting very close to the
star, at a distance of about 10 stellar radii. That's less than one-tenth
the size of Mercury's orbit in our solar system.

"In a two-day orbit , it's about 200 degrees Celsius too hot for liquid
water," Butler said. "That tends to lead us to the conclusion that the most
probable composition of this thing is like the inner planets of this solar
system a nickel-iron rock, a rocky planet, a terrestrial planet."

"The planet's mass could easily hold onto an atmosphere," noted Laughlin,
an assistant professor of astronomy at UC Santa Cruz. "It would still be
considered a rocky planet, probably with an iron core and a silicon mantle.
It could even have a dense steamy water layer. I think what we are seeing
here is something that's intermediate between a true terrestrial planet
like the Earth and a hot version of the ice giants Uranus and Neptune."

Combined with improved computer software, the new CCD (charge coupled
device) detectors designed by this team for Keck's HIRES spectrometer can
now measure the Doppler velocity of a star to within one meter per
second human walking speed instead of the previous precision of three
meters per second. This improved sensitivity will allow the planet-hunting
team to detect the gravitational effect of an Earth-like planet within the
habitable zone of M dwarf stars like Gliese 876.

"We are pushing a whole new regime at Keck to achieve one meter per second
precision, triple our old precision, that should also allow us to see
Earth-mass planets around sun-like stars within the next few years," Butler
said.

"Our UC Santa Cruz and Lick Observatory team has done an enormous amount of
optical and technical and detector work to make the Keck telescope a rocky
planet hunter, the best one in the world," Marcy added.

Lissauer also is excited by another feat reported in the paper submitted to
the journal. For the first time, he, Rivera and Laughlin have determined
the line-of-sight inclination of the orbit of the stellar system solely
from the observed Doppler wobble of the star. Using dynamical models of how
the two Jupiter-size planets interact, they were able to calculate the
masses of the two giant planets from the observed shapes and precession
rates of their oval orbits. Precession is the slow turning of the long axis
of a planet's elliptical orbit.

They showed that the orbital plane is tilted 40 degrees to our line of
sight. This allowed the team to estimate the most likely mass of the third
planet as seven and a half Earth masses.

"There's more dynamical modeling involved in this study than any previous
study, much more," Lissauer said.

The team plans to continue to observe the star Gliese 876, but is eager to
find other terrestrial planets among the 150 or more M dwarf planets they
observe regularly with Keck.

"So far we find almost no Jupiter-mass planets among the M dwarf stars
we've been observing, which suggests that, instead, there is going to be a
large population of smaller mass planets," Butler noted.

Esta mañana me llegó el anuncio de rueda de prensa. Mola :)

Acabo de leer este anuncio de posibles planetas girando alrededor de sus correspondientes estrellas; te lo envío por si te puede interesar. Papi.

Intentando enviarte este anuncio, de las etrellas con planetas, de repente veo que tú también ya me lo enviaste. Nos hemos cruzado en la idea. Un abrazo a todos. Papi.

Hola Pedro, ¿nos estamos enviando, a la vez, lo mismo? ¿qué significa url? ¿sin el url te llegó mi mensaje anterior y quizás éste también, y a la vez, en el margen de media hora?