Astronomers spot largest collection of planets orbiting sun-like star

Astronomers use the European Southern Observatory to spot solar system similar to our own

ESO view of HD10180
Astronomers using the European Southern Observatory say they have spotted a solar system similar to ours containing seven planets as compared to our eight. The researchers also found evidence that the distances of the planets or exoplanets from their star follow a regular pattern similar to our solar system.

The international team of astronomers made the discovery using used the HARPS spectrograph which is attached to ESO's 3.6-meter telescope at La Silla, Chile, during a six-year-long study of the Sun-like star labeled HD 10180, located 127 light-years away in the southern constellation of Hydrus.

Amazing telescopes produce hot space images

"We have found what is most likely the system with the most planets yet discovered," Christophe Lovis, lead author of the paper reporting the findings said in a statement.

Using 190 individual HARPS measurements, the astronomers detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets. The five strongest signals correspond to planets with Neptune-like masses -- between 13 and 25 Earth masses -- which orbit the star with periods ranging from about 6 to 600 days. These planets are located between 0.06 and 1.4 times the Earth-Sun distance from their central star, the team stated.  On average the planets in the inner region of the HD 10180 system have 20 times the mass of the Earth, whereas the inner planets in our own Solar System -- Mercury, Venus, Earth and Mars -- have an average mass of half that of the Earth, the astronomers stated.

"We also have good reasons to believe that two other planets are present," Lovis, said. "One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth-Sun distance. One 'year' on this planet would last only 1.18 Earth-days."

The planets around HD 10180 are unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits, the team stated.

So far, astronomers know of fifteen systems with at least three planets. The last record-holder was 55 Cancri, which contains five planets. "Systems of low-mass planets like the one around HD 10180 appear to be quite common, but their formation history remains a puzzle," according to Lovis.

The news comes ahead of a scheduled NASA teleconference slated for Aug. 26, where it will talk about its star-gazing Kepler spacecraft's discovery of what the space agency called "an intriguing planetary system."  Kepler looks for the data signatures of planets by measuring tiny decreases in the brightness of stars when planets cross in front of, or transit, them. In June, mission scientists announced the mission has identified more than 700 planet candidates.

NASA reported earlier this year the Kepler space telescope spotted five new planets orbiting stars beyond our own solar system.  The five planets are called "hot Jupiters" because of their deep mass and extreme temperatures, NASA said. They range in size from about the same size as Neptune to larger than Jupiter and have orbits ranging from 3.3 to 4.9 days, NASA stated. The orbs likely have no known living organisms because NASA estimates their temperatures to range from 2,200 to 3,000 degrees Fahrenheit, hotter than molten lava and all five orbit stars hotter and larger than Earth's sun.

On station since May 2009, Kepler scans more than 150,000 stars and looks for the signatures of planets by measuring dips in the brightness of stars. When planets cross in front of, or transit, their stars as seen from Earth, they periodically block the starlight. The size of the planet can be derived from the size of the dip. The temperature can be estimated from the characteristics of the star it orbits and the planet's orbital period. Kepler will continue operations until at least November 2012, NASA stated.

Follow Michael Cooney on Twitter: nwwlayer8  

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