As the most common type of star in the galaxy, astronomers long wondered if planets orbited any red dwarfs. Since then several worlds have been found orbiting these stars including the small exoplanet orbiting the red dwarf star '''OGLE-2005-BLG-390L''' with a mass of only 5.5 times that of the Earth.<ref>http://www.nature.com/nature/journal/v439/n7075/full/nature04441.html</ref> This was the smallest known exoplanet until the discovery of a planet in orbit of [[Gliese 581]] in 2009 called [[Gliese_581#Gliese_581_e|Gliese 581 e]], which has a mass only 1.9 times the Earth.<ref>http://exoplanets.org/planets.shtml</ref> The red dwarf Gliese 581 also has a world, [[Gliese_581#Gliese_581_d|Gliese 581 d]], which is presently considered a decent candidate for habitability as it sits within the [[habitable zone]] of its parent star.<ref>http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...476.1365V&db_key=AST&nosetcookie=1</ref> | As the most common type of star in the galaxy, astronomers long wondered if planets orbited any red dwarfs. Since then several worlds have been found orbiting these stars including the small exoplanet orbiting the red dwarf star '''OGLE-2005-BLG-390L''' with a mass of only 5.5 times that of the Earth.<ref>http://www.nature.com/nature/journal/v439/n7075/full/nature04441.html</ref> This was the smallest known exoplanet until the discovery of a planet in orbit of [[Gliese 581]] in 2009 called [[Gliese_581#Gliese_581_e|Gliese 581 e]], which has a mass only 1.9 times the Earth.<ref>http://exoplanets.org/planets.shtml</ref> The red dwarf Gliese 581 also has a world, [[Gliese_581#Gliese_581_d|Gliese 581 d]], which is presently considered a decent candidate for habitability as it sits within the [[habitable zone]] of its parent star.<ref>http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...476.1365V&db_key=AST&nosetcookie=1</ref> |