Search for Planets
Formation of the Solar System
No planets satisfying all the above requirements have yet been found. But detection techniques are becoming more and more sophisticated, and we can expect the discovery of habitable planets in the near future. Furthermore, it is now reasonable to plan for telescopes that will look at the spectra of planetary atmospheres to find any indications for the presence of life in the form of absorption features of water or ozone.
Whether the aim is to understand the formation of planets or to look for extraterrestrial life, more observational and theoretical work is needed.
The quest for extrasolar planets will be revolutionized by Gaia, an astrometric satellite that the European Space Agency will launch about 2011. Gaia will detect about 10 000 Jupiter-mass planets, depending on details of the detection and orbital distribution hypotheses. Such a large sample would be fundamental for testing theories of the formation and evolution of planetary systems.
The diagram below shows the already known extrasolar planets distributed according to their masses (the number of known planets refers to our knowledge in mid 2007):