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Astronomy in the News

Mercury Autumn 2010 Table of Contents


artist's impression of planetary system

This artist's impression shows the remarkable planetary system around the Sun-like star HD 10180 — five planets and evidence for two more. The large crescent is the third world in the system, which is comparable to the planet Neptune in mass.
Credit: ESO / L. Calçada.

Richest Planetary System Discovered

European Southern Observatory

Astronomers using ESO's world-leading HARPS instrument have discovered a
planetary system containing at least five planets, orbiting the Sun-like star HD 10180. The researchers also have tantalizing 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 the Solar System's eight planets). Furthermore, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our solar system.

"We have found what is most likely the system with the most planets yet discovered," says Christophe Lovis, lead author of the paper reporting the result. "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 newly discovered system of planets around HD 10180 is 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.


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