Sep. 12, 2011 at 1:51 PM ET
European astronomers have announced the discovery of more than 50 new planets beyond our solar system, including 16 that are just a notch above our own planet in mass. They say their record-breaking findings suggest that more than half of the stars like our sun possess planets, and that many of those worlds are less massive than Saturn.
The pick of the litter is a planet that's already been in the spotlight: HD 85512 b, a world at least 3.6 times as massive as Earth that's located 36 light-years away in the constellation Vela. HD 85512 b is the only one of the 16 super-Earths on today's list that is located in its star system's habitable zone. That's the area around a star where scientists believe water could exist in liquid form, which would make a rocky planet potentially livable.
HD 85512 b's status came to light a couple of weeks ago in a paper submitted to the journal Astronomy and Astrophysics, but the team behind the discovery provided more details about that super-Earth and the dozens of other worlds in papers presented today at the Extreme Solar Systems II conference in Wyoming.
The findings came from the team behind the High Accuracy Radial Velocity Planet Searcher, or HARPS, which is installed at the European Southern Observatory's 11.8-foot (3.6-meter) La Silla Observatory in Chile.
"The detection of HD 85512 b is far from the limit of HARPS, and demonstrates the possibility of discovering other super-Earths in the habitable zones around stars similar to the sun," University of Geneva astronomer Michel Mayor said in today's news release from the ESO.
Super-Earths, which range from Earth's mass to worlds 10 times more massive, are of particular interest to planet-hunters because it's thought that they could be even more conducive to the development of life than our own planet. When the search for extrasolar planets began more than 15 years ago, the telescopes used for the task could only detect giant planets like our own solar system's Jupiter. Since then, the techniques and tools used for the search have become much more sensitive.
HARPS, for example, can detect the slight gravitational wobble caused by planets as small as Earth, if they have incredibly close-in orbits. HARPS' observations of 376 sunlike stars has led the team to conclude not only that more than half of such stars are surrounded by planets (maybe as many as 70 or 80 percent), but also that about 40 percent of sunlike stars have at least one planet less massive than Saturn.
One of the team members, Lisa Kaltenegger of the Max Planck Institute for Astronomy and the Harvard Smithsonian Center for Astrophysics, told journalists today that the latest round of findings marked a new age in the search for habitable planets.
"We are actually entering an incredibly interesting time in our history," she said.
Keeping track of the habitables
ESO's Markus Kissler-Patig said the discovery of HD 85512 b could be one of the first entries in "a good catalog of habitables" marked for further study. Kissler-Patig is the project scientist for the ESO's European Extremely Large Telescope, or E-ELT, which is slated to be built over the next decade at a cost of 1 billion euros ($1.4 billion).
HD 85512 b "is in the zone where we can directly image it," Kissler-Patig said, and that means astronomers could theoretically analyze its atmosphere for the signatures of life, such as the presence of oxygen, methane and water vapor.
The HARPS team members were able to figure out the minimum mass and orbital characteristics of HD 85512 b, but they couldn't determine its density, composition or the nature of its atmosphere — which means astronomers will have to wait for the completion of E-ELT or similar high-resolution observing instruments to confirm that the world is truly habitable.
Francesco Pepe, a colleague of Mayor's at the University of Geneva, said that the HARPS team's discoveries include 10 worlds described in papers submitted to Astronomy and Astrophysics, including HD 85512 b, and 49 planets reported today at the Wyoming conference. Eight of the new planets were detected as part of the Swiss-led CORALIE search effort in Chile, he said. The ESO says this is the largest number of extrasolar planets reported at one time.
Pepe said the findings pointed up a fresh mystery for planet-hunters to ponder: the existence of a "planet desert" between low-mass worlds and gas giants. Relatively few planets have been found at a level around 30 times the mass of Earth. "It may point towards different formation mechanisms" for planets like Earth and Neptune vs. planets like Jupiter and Saturn.
HARPS isn't the only instrument engaged in the search for extrasolar planets: Two space telescopes, NASA's Kepler and the European Space Agency's Corot, are detecting planets by looking for the telltale dimming of their parent stars. Kepler and Corot can determine how big a planet is, but they can't tell how massive it is. In contrast, HARPS can determine the mass but not the size.
Unfortunately, Kepler can't be used to confirm HARPS' discoveries, nor can HARPS confirm Kepler's. The good news is that the William Herschel Telescope in the Canary Islands is being outfitted for a HARPS North instrument that will begin operation next year and facilitate the follow-up of Kepler detections.
Today's revelations bring the official tally of extrasolar planets to 645.
Other findings from the Extreme Solar Systems II conference:
• Over at the "Dynamics of Cats" blog, Steinn Sigurdsson quotes Kepler team members as saying they have identified 1,781 candidate planets, with up to 27 of those confirmed. Among the reported candidates are 123 potential worlds that are less than 1.25 times as wide as Earth, and 121 that are in the nominal habitable zones of their parent stars.
• Astronomers say they have observed brightness changes on a failed star, also known as a brown dwarf, that may indicate a storm grander than any seen yet on a planet. The stormy brown dwarf is known as 2MASS 2139.
"We found that our target's brightness changed by a whopping 30 per cent in just under eight hours," the University of Toronto's Jacqueline Radigan said in a news release. "The best explanation is that brighter and darker patches of its atmosphere are coming into our view as the brown dwarf spins on its axis."
Radigan is the lead author of a paper being presented this week at the Extreme Solar Systems II conference.
More about alien planets:
Authors of “The HARPS search for Earth-like planets in the habitable zone, I — Very low-mass planets around HD20794, HD85512, HD192310" include F. Pepe, C. Lovis, D.D. Ségransan, W. Benz, J. L. Bertaux , F. Bouchy, X. Dumusque, M. Mayor, D. Queloz, N.C. Santos and S. Udry.
Authors of "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets" include M. Mayor, M. Marmier, C. Lovis, S. Udry, D.D. Ségransan, F. Pepe, W. Benz, J. L. Bertaux , F. Bouchy, X. Dumusque, G. Lo Curto, C. Mordasini, D. Queloz and N.C. Santos.
Authors of "High amplitude, periodic variability of a cool brown dwarf: Evidence for patchy, high-contrast cloud features" include Jacqueline Radigan, Ray Jayawardhana, David Lafreniere, Etienne Artigau, Mark Marley and Didier Saumon.
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