Gliese 581

Gliese 581 is a red dwarf star with spectral type M3V, located 20.3 light years away from Earth. Its mass is estimated to be approximately a third of that of the Sun, and it is the 87th closest known star system to the Sun. Observations suggest that the star has at least four planets: Gliese 581 b, c, d, e.
==Observations==
Gliese 581 is known at least from 1886, when it was included in Eduard Schönfeld's Southern Durchmusterung (SD)—the fourth part of the Bonner Durchmusterung.
The name Gliese 581 refers to the catalog number from the 1957 survey Gliese Catalogue of Nearby Stars of 965 stars located within 20 parsecs of the Earth. Other names of this star include BD-07° 4003 (BD catalogue, first known publication) and HO Librae (variable star designation). It does not have an individual name such as Sirius or Procyon. 
==Star==
The star is a red dwarf with spectral type M3V, located 20.5 light-years away from Earth. It is located about two degrees north of Beta Librae, the brightest star in the Libra constellation. Its mass is estimated to be approximately a third that of the Sun, and it is the 101st closest known star system (including brown dwarfs) to the Sun. 
Gliese 581 is a very old star. Its slow rotation makes it very inactive, making it better suited than most red dwarfs for having habitable planets. It is also classified as a variable star of the BY Draconis type, and has been given the variable star designation HO Librae. This is a star that exhibits variability because of the presence of star spots combined with the rotation of the star. It also emits X-rays
==Planetary system==
Gliese 581 e - Confirmed - 1.657 M🜨 - 0.029 AU
Gliese 581 b - Confirmed - 15.20 M🜨 - 0.041 AU
Gliese 581 c - Confirmed - 5.652 M🜨 - 0.074 AU
Gliese 581 g - Confirmed - 3.1 M🜨 - 0.146 AU
Gliese 581 d - Confirmed - 6.98 M🜨 - ~0.218 AU
Gliese 581 f - Confirmed - 7.0 M🜨 - 0.7 AU
Category:Stars
Category:Planetary systems
Category:Gliese 581 System
Category:Libra constellation