Reaching for the stars to find new worlds
Extrasolar planets, also known as exoplanets, are planets whose address lies outside our solar system. Unsurprisingly, given that they raise the intriguing possibility of detecting worlds similar to our own, exoplanets have been the object of study since the 19th century. Since planets are outshone by stars, it is only recently that we have had the technology to find some, with the first confirmed detection in 1992. Although there are probably more than 50 billion planets in our galaxy, only some 700 have been identified to date. One area that has been neglected by the hunt is low-mass stars. The 'Searching for extrasolar planets around the lowest mass stars' (Exoplanet Search) project focused on an area of the night sky that had hitherto been neglected: the lowest mass stars, which are the most numerous in our galaxy. Advances in this direction promised to help illuminate the correlation between stellar mass and planet formation. The radial velocity method was employed, applying it for the first time with high precision to the near infrared (nIR) spectral regime in order to sidestep the problems of stellar faintness and activity. The project clocked up 33 observation nights at the Very Large Telescope (VLT) facility located at the European Southern Observatory (ESO). Exoplanet Search demonstrated the radial velocity measurement precision that had been predicted and aimed for. This level of precision opened the door for the planet search to begin in earnest. The project not only managed to detect some candidate planets but also succeeded in refuting a previous detection claim which was reached through astrometry. Initial analysis revealed that available data was not sufficient to confirm the candidate planets and so further observation (of greater than 100 days) is required in order to properly identify and characterise them. The team carried out a similar project at the Subaru telescope, which grants access to stars in the northern hemisphere. Researchers were able to increase their sample size and obtain better statistics for constraining planet formation theory. Project partners also worked on a complementary project to develop a methodology for investigating the atmospheres of low-mass transiting planets which led to the first spectrum of a low-mass exoplanet.
