Scientists including NASA's Nancy Kiang have proposed that the existence of Acaryochloris marina suggests that organisms that use Chlorophyll d, rather than Chlorophyll a, may be able to perform oxygenic photosynthesis on exoplanets orbiting red dwarf stars (which emit much less light than the Sun).
Frontiers of Astrobiology is a non-fiction book edited by astronomers Chris Impey, Jonathan Lunine, and José Funes that summarizes the state of our understanding of life on Earth, the search for exoplanets, and the prospects for life elsewhere.
Present day searches for exoplanets are insensitive to exoplanets located at the distances from their host star comparable to the semi-major axes of the gas giants in the Solar System, greater than about 5 AU.
Hot Jupiters - a class of exoplanets like the one around Pegasi 51 (51 Pegasi b)