EXOPLANET SEARCH

Searching for extrasolar planets around the lowest mass stars

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 Obiettivo del progetto (Objective)

'The main aim of the proposed project is to search for planets around nearby stars that are of a hitherto ignored stellar type using newly developed technology and methodology to improve our understanding of planet formation and evolution. The specific focus will be on the lowest mass stars. Stars of this type are a crucial sample of potential planet hosts because they can be used to illuminate the correlation between stellar mass and planet formation, are the most numerous kind of stars in the galaxy, and allow lower mass planets to be identified for a given level of observational precision. The technique employed will be the radial velocity method, but applied 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. Observation time at the ESO VLT for the survey amounting to 33 nights over two years has already been granted to the applicant. A new gas absorption cell designed by the applicant will be used with an existing instrument to measure high precision nIR radial velocities for the first time. The ancillary goals of the project will be to do follow-up study of any detected planets using complementary observational techniques, elucidate the advantages and disadvantages of nIR radial velocities, and explore additional research enabled by the methods and technology developed for the core program. The applicant possess the unique combination of experiences necessary to carry out this full program. The Institute for Astrophysics of the University Goettingen is the proper location for such a project due to the experience of its staff, access to facilities, and international collaborations. The main impacts of the program will be demonstration of a new planet detection technique, broadening the research scope of a recognized node of extrasolar planet science in the EU, and the first scientific data about planets around the lowest mass stars.'

Introduzione (Teaser)

An EU-funded study took a novel approach to detecting new candidate planets. Project outcomes pave the way for further research on low-mass stars.

Descrizione progetto (Article)

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.