Another Jupiter Twin Found in Flood of Planet Discoveries

Space.com ^ | 6/19/02 | Robert Roy Britt and Tariq Malik

[Brett66]

Another Jupiter Twin Found in Flood of Planet Discoveries

By Robert Roy Britt
Senior Science Writer
and Tariq Malik
Staff Writer

WASHINGTON, D.C. - European astronomers announced this week the discovery of a Jupiter-like planet around another star, a finding that comes less than a week after a similar announcement of a Jovian lookalike around another star by a U.S.-led team.

The latest discovery is a gas giant world similar in mass to Jupiter in an orbit at 3.7 astronomical units (AU). One AU is the distance from Earth to the Sun. Jupiter orbits at 5.2 AU.

Though the discovery does not reveal whether any Earth-like planets might also orbit the star, it leaves the door wide open.

"There is space for terrestrial planets in the inner regions," the Geneva Observatory's Stephane Udry, one of the discoverers, said in an interview.

If such terrestrial (rocky) planets exist, the system would be more similar to our solar system than any presently known. Most astronomers agree it will be several years before technology allows the detection of Earth-sized planets, however.

Last week, a planet-hunting team led by Geoffrey Marcy of the University of California, Berkeley, announced the first extrasolar planet with a mass and orbit similar to Jupiter. That planet's orbit was elongated and not circular, like Jupiter's, however.

The European team has found a planet whose orbit is nearly circular. Such orbits are seen as important for the creation of stable planetary systems.

The discovery was presented at a press conference here at the Carnegie Institution during a four-day meeting titled "Scientific Frontiers in Research on Extrasolar Planets."

The Geneva researchers also announced 11 other newfound planets, all large and closer to their host stars than the Jovian tiwn. Some of these planets were also found by Marcy's team and announced last week, so it is unclear at the moment how many extrasolar planets, all totaled, have been found. The count is above 100, however.

Combined, the discoveries are the culmination of years of data gathering and they point the way to the next era of planet hunting in which astronomers will search for worlds more like Earth.

"The first planets we detected were the ones with short periods, completing an orbit in just a few days," said Didier Queloz, who is also on the Geneva team. "They were the easiest to detect because they give the largest signals."

Astronomers find most extrasolar planets indirectly by watching the stars they circle. The planet's gravity causes its parent star to wobble, just slightly, but enough to be measured from Earth.

"Now we can see long period planets, we can check for multiple planets in systems already known to contain a single planet and check for Jupiter analogues that may indicate solar systems like our own," Queloz said.

The Jupiter-like planet found by the European team orbits its host star in about seven years, a few short of the nearly 12 it takes Jupiter to round the Sun.

Improved ground instruments, astronomers say, could make earthbound observations 100 times better, and one such tool -- the High Accuracy Radial velocity Planetary Search (HARPS) spectrograph, will soon be installed onto the European Southern Observatory's La Silla Observatory in Chile.

Scientists also hope to spot other planets using a transit-method, which measures the change in a star's light output as a planet crosses between it and observers on Earth.

Meanwhile, both NASA and the European Space Agency are looking toward space as a better home base to fish for planets.

NASA has two missions planned over the next decade. Kepler, slated to launch in 2007, will attempt to generate a census of Earth-like planets around Sun-like stars, but it will only detect them -- no photographs will be possible. Later, the Terrestrial Planet Finder is slated to make the first images of Earth-like planets around other stars, assuming they exist.

Queloz serves on the scientific advisory group for the ESA's Darwin project, a plan to send a flotilla of eight spacecraft, flying in formation, detect and photograph Earth-like planets and search their atmospheres for signs of life. The project is still in the planning stage and is expected to fly in the middle of the next decade.

In addition to Darwin, the ESA plans to launch a pair of missions under the agency's Cosmic Vision 2020 program to study stars and find more planets. The spacecraft Eddington, set for a 2008 liftoff, will search for planets and detect the equivalent of earthquakes on the surface of stars. In 2012, ESA plans to launch Gaia to survey the nearest one billion stars for precise data of their position and brightness, and search for extrasolar planets using the wobble and transit-methods.

"They are essential," Queloz said of all three European efforts, adding that putting a planet-seeking eye in space will be the only way to reach Earth-like systems. "Eddington will detect ten or a hundred times more planets than we can from the ground."

Particularly exciting, he added, is the Darwin mission, because looking for evidence of life on other worlds is one of the pillars supporting planet-hunting quests. Queloz is optimistic about Darwin's chances of finding life, in one form or another, in the planets it locates.

"Why should Earth be a kind of strange system with life?" he asked, adding that finding other intelligence in space may be rare - the chances might even be just one civilization in a galaxy. "But for basic life, I'm sure it has to be there."

[Brett66]

This is a different discovery from the 55 Cancri find a few days ago.

[SunkenCiv]

Note: this topic is from nearly five years ago. Thank you.

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