Astronomers Discover Planetary System Containing at Least Five Planets
Posted on April 6, 2012
Astronomers using ESO's HARPS instrument have discovered a planetary system containing at least five planets. This is the most planets found on a planetary system to date. The planets orbit Sun-like star HD 10180. The researchers also have evidence that two other planets may be present, one of which would have the lowest mass ever found. This would make the system similar to our Solar System in terms of the number of planets (seven as compared to our Solar System's eight planets). The astronomers also say they found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System. The artist's impression above shows the planetary system around the Sun-like star HD 10180.
Christophe Lovis, lead author of the paper, says, "We have found what is most likely the system with the most planets yet discovered. This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system."
The team of astronomers used the HARPS spectrograph for a six-year study of HD 10180, which is located 127 light-years away in the southern constellation of Hydrus. 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.
Lovis says, "We also have good reasons to believe that two other planets are present."
Lovis says one of the planets 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 about 2% percent of the Earth-Sun distance. One year on this planet would last just 1.18 Earth-days.