The discovery of exoplanets is becoming more and more commonplace. Even though nearly 500 planets have been discovered so far new discoveries are hardly dull, routine news – well not for me they aren’t.
Still, we have gotten to a point where a new discovery has to be fairly spectacular to be a major news item. This is certainly the case with the discovery of a planetary system containing at least five planets orbiting the star HD 10180. The star, which is similar to the Sun, is 127 light years away, in the southern constellation of Hydrus.
Christophe Lovis from Geneva University's observatory in Switzerland was lead researcher on the study. He said that his team had probably found "the system with the most planets yet discovered.... This 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," he said.
The High Accuracy Radial velocity Planet Searcher (or Harps) at the European Sothern Observatory in Chile was responsible for the discovery. Harps measures the wobble of a star; this gives a measure of how much it is being tugged on by an orbiting planet.
Using Harp, Dr Lovis and his team were able to measure the star’s wobble this and break it down, in order to calculate how many planets were in the system, how great each of their masses was, and even the path of each individual planet's orbit.
HD 10180 is unique in several respects. It has at least five "Neptune-like planets" lying within a distance equivalent to the orbit of Mars, making it more populated than our own Solar System in its inner region. And all the planets seem to have almost circular orbits.
So far, the astronomers have picked up clear signals from five planets, along with two slightly "fuzzier" signals. One of these possible sixth and seventh planets was estimated to be just 1.4 times the mass of the Earth; if its presence in the system was confirmed, it would be the lowest mass exoplanet yet discovered. It is also predicted to be very close to its host star - just 2% of the Earth-Sun distance, so one year on this planet would last only 1.2 Earth days.
Now this is a spectacular discovery. It makes me wonder what will be next.