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| parallax        =160.91 ± 2.62  mas

| parallax        =160.91 ± 2.62  mas

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'''Gliese 581''', also known as '''HO Librae''', is a red dwarf star around 20.4 [[light year|light years]] away.  It is most famous for the discovery of the [[Gliese 581c|first low mass planet within a star's habitable zone]].  In total, four planets have found thus far orbiting the star, two of which may sit within the [[habitable zone]].

'''Gliese 581''', also known as '''HO Librae''', is a red dwarf star around 20.4 [[light year|light years]] away.  It is most famous for the discovery of the [[Gliese 581c|first low mass planet within a star's habitable zone]].  In total, four planets have found thus far orbiting the star, two of which may sit within the [[habitable zone]].

==The Star==

==The Star==

Gliese 581 is a cool, dim, [[red dwarf]] in the main sequence with the spectral classification of M3 V.  The star is one-third as massive as our own [[Sun]], with around 38 percent of its diameter.  The star is only one percent as luminous as our Sun.  However, much of the light emanating from Gliese 581 is in the infrared, therefore visually it is only 0.2 percent as bright.  The star’s [[metallicity]] appears to be between 38 and 62 percent as enriched as our [[Sun]], according to its abundance of [[iron]].  Using measurements of Gliese 581’s kinematic characteristics and magnetic activity, the star is calculated to be at least 2 billion years old, possibly as old as 4.3 billion years.<ref name="exo">http://exoplanet.eu/star.php?st=Gl+581</ref>  More recent measurements of the star shows its brightness only varies slightly over time, suggesting it is even older.<ref>http://www.astronomy.com/asy/default.aspx?c=a&id=5619</ref>

Gliese 581 is a cool, dim, [[red dwarf]] in the main sequence with the spectral classification of M3 V.  The star is one-third as massive as our own [[Sun]], with around 38 percent of its diameter.  The star is only one percent as luminous as our Sun.  However, much of the light emanating from Gliese 581 is in the infrared, therefore visually it is only 0.2 percent as bright.  The star’s [[metallicity]] appears to be between 38 and 62 percent as enriched as our [[Sun]], according to its abundance of [[iron]].   

==Planetary System==

==Planetary System==

The planet has a mean orbit of only 0.03 AU, which it completes in a mere 3 days.  Because of its short distance, the planet is too close to be within Gliese 581’s habitable zone.<ref name="exo">http://exoplanet.eu/star.php?st=Gl+581</ref>  It is unlikely to have an atmosphere because of the high temperatures and strong [[radiation]] it would receive at such a close distance to even a low mass [[star]].   

The planet has a mean orbit of only 0.03 AU, which it completes in a mere 3 days.  Because of its short distance, the planet is too close to be within Gliese 581’s habitable zone.<ref name="exo">http://exoplanet.eu/star.php?st=Gl+581</ref>  It is unlikely to have an atmosphere because of the high temperatures and strong [[radiation]] it would receive at such a close distance to even a low mass [[star]].   

[[Category:Astronomy]]

[[Category:Astronomy]]