Gliese 876

Gliese 876 is a red dwarf star located 15.2 light-years from Earth in the constellation of Aquarius. It is one of the closest stars to the Sun known to have a planetary system with more than two planets. As of 2018, four extrasolar planets have been discovered orbiting Gliese 876.

This planetary system is special because of how its planets move. The planets show a rare pattern called Laplace resonance, where they line up in a special way. This is similar to how some of Jupiter's moons move.

Although two of Gliese 876's planets are in the area where liquid water could exist, they are large gas planets similar to Jupiter, not places where life as we know it could live. Gliese 876 is also the first system around a normal star where scientists have been able to measure how flat, or coplanar, the orbits of the planets are.

Distance and visibility

Gliese 876 is located fairly close to the Solar System. According to astrometric measurements made by the Gaia spacecraft, the star is 15.238 ly from Earth. Even though it is close, the star is so faint that it cannot be seen without a telescope.

Stellar characteristics

Gliese 876 is a red dwarf star, which means it is smaller and cooler than our Sun. It has only about 35% of the Sun’s mass and shines much less brightly, with just 1.3% of the Sun’s luminosity. Most of its light is given off as infrared radiation.

This star’s brightness changes slightly, varying by about 0.04 magnitudes, due to large dark spots rotating across its surface, similar to sunspots. These changes were first noticed by Edward W. Weis, and the star was given the variable star name IL Aquarii in 1997. Like many red dwarfs, Gliese 876 also gives off X-rays.

Planetary system

Gliese 876 is a red dwarf star with four known planets orbiting it. The first planet, Gliese 876 b, was found in 1998. A second planet, Gliese 876 c, was discovered in 2001, followed by Gliese 876 d in 2005 and Gliese 876 e in 2010. These planets have interesting orbits, with some moving in patterns similar to the moons of Jupiter.

The innermost planet, Gliese 876 d, is likely a rocky world. Gliese 876 c is a giant planet that might support life on any large moons it could have. Gliese 876 b is a large planet that orbits very close to its star, and Gliese 876 e is similar in size to the planet Uranus.