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Gliese 581

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description Gliese 581 Overview

Gliese 581 is a cool red-dwarf star in the constellation Libra, about 20 light-years from Earth. It became a widely studied nearby stellar system after astronomers reported several planets through radial-velocity observations, including Gliese 581 b, c, d, and e at different stages of confirmation. Later analyses showed that some reported signals could be caused by stellar activity, so the system is also used to illustrate the difficulty of distinguishing planets from variations in a star's light and motion.

help Gliese 581 FAQ

What kind of star is Gliese 581?

Gliese 581 is a cool M-type red dwarf in Libra, roughly 20 light-years from Earth. Its low mass and faint red light made it an important target for early nearby exoplanet searches.

How were the planets around Gliese 581 detected?

Astronomers used the radial-velocity method, measuring small Doppler shifts caused by a planet's gravity pulling its star back and forth. Reports of planets such as Gliese 581 b, c, d, and e made the system a major case study in interpreting weak signals.

Are all of the reported Gliese 581 planets confirmed?

No. NASA has described Gliese 581 b, c, and e as confirmed, while signals associated with Gliese 581 d and especially the proposed planet g have been challenged by stellar activity. [NASA Astrobiology](https://astrobiology.nasa.gov/news/not-a-planet-after-all/)

Why did Gliese 581 become associated with potentially habitable planets?

Gliese 581 c and d were reported as orbiting at distances that prompted discussion of surface conditions and liquid water. Those claims were scientifically important but uncertain because red-dwarf activity can imitate planetary radial-velocity signals.

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