Richest known planetary system discovered from Chile

A six-year study at the European Southern Observatory’s center at La Silla, Chile reveals a system of at least five, and as many as seven planets, the most ever discovered outside our own solar system.


Scientists at the European Southern Observatory at La Silla, Chile, discovered the richest system of planets outside our own solar system using the HARPS spectograph – the most advanced extrasolar planet hunter in the world.

The ESO center at La Silla has long been a groundbreaking center for astronomy. Located 600 km north of Santiago on the fringes of the Atacama Desert, it takes advantage of some of the darkest night skies on earth to gather information on the minute motions of distant stars. The stars reveal patterns caused by the gravitational pulls of surrounding planets.

A six-year study of the sun-like star HD 10180 has yielded the definitive discovery of five planets and evidence of two more. The five planets discovered to date are roughly the size of Neptune and all orbit their star at a distance no greater than that of Mars around our Sun, making this system far denser at its core than our own.

Two possible planets remain unconfirmed, one roughly the size of Saturn orbiting the star every 2200 days, and a second that would be the least massive planet ever discovered outside our Solar System – only 1.4 times larger than earth’s, and an orbital period of a mere 1.18 earth days. These planets have been more difficult to confirm due to their comparatively small gravitational pulls on HD10180.

As of now, the system of planets around HD 10180 is one of only 15 planetary systems yet discovered containing more than three planets. If the final two are confirmed, the system surrounding HD10180 will be roughly the same size as our own, with seven planets compared to our eight.

The planets discovered to date all have roughly circular orbits and are spaced – like the planets of our Solar System – at regular distances from their star. Astronomers are hopeful that the information gathered thus far by the HARPS device will help shed light upon the evolution of this system and others like it, particularly our own.