Gliese 876 c

Gliese 876 c is an exoplanet exoplanet, which means it is a planet that orbits a star outside our solar system. It goes around a small, cool star called a red dwarf red dwarf, named Gliese 876 Gliese 876. It takes about 30 days days to finish one orbit, much quicker than Earth takes to orbit the Sun.

The planet was discovered in April 2001, and it was one of the first exoplanets scientists found. It is the second planet from its star, and another planet is even closer to Gliese 876. By studying planets like Gliese 876 c, scientists can learn more about how solar systems are made and how common Earth-like planets might be around distant stars.

Discovery

Scientists studied the star Gliese 876 and found it already had one planet, called Gliese 876 b. On January 9, 2001, they found a second planet, named Gliese 876 c. They discovered this by watching how the star's movement changed over time, called its radial velocity. Gliese 876 c orbits its star in half the time it takes the farther planet. This made scientists first think the first planet's orbit looked different than it really was.

Host star

Main article: Gliese 876

The planet Gliese 876 c orbits a small, cool star named Gliese 876. This star is smaller and cooler than our Sun. It has about a third of the Sun’s size and mass. The star has been shining for 2.55 billion years.

Orbit and mass

Gliese 876 c moves in a special pattern called a 1:2:4 Laplace resonance with two other planets, Gliese 876 b and Gliese 876 e. This means that for every orbit planet e makes, planet b makes two orbits and planet c makes four orbits. We first saw this pattern with Jupiter's moons Io, Europa, and Ganymede.

The planet is very close to its star, about a third of the distance between Mercury and the Sun. Even though it is close, it might have liquid water because its star gives off very little light. Scientists think the planet’s mass is about 0.72 times the mass of Jupiter.

Characteristics

Gliese 876 c is likely a gas giant, meaning it doesn’t have a solid surface like Earth. We found it by how it affects its star, so we don’t know its exact size, what it’s made of, or its temperature. Scientists think it might have a clear upper atmosphere.

The planet orbits at the inner edge of its star’s habitable zone. This is the area around a star where liquid water could exist on a planet’s surface. Even though gas giants may not support life themselves, a large moon orbiting this planet might have the right conditions for life. However, the pull from the star and planet could make such moons move away too quickly to stay in the right place for life.