This animation shows the newly discovered planet and its two larger siblings as they orbit the M dwarf star Gliese 876. The star and the orbits are to scale; the planet sizes are exaggerated. In addition, the orbits are shown inclined at an angle of 50 degrees, which is how they appear in our sky.

The outermost planet, known as Gliese 876b, was discovered in 1998. It orbits the star once every 61 Earth days, and has about twice the mass of Jupiter, our own solar system's largest planet. That makes it roughly 600 times the mass of the Earth. The middle planet, Gliese 876c, was discovered in 2001. It orbits the star once every 30 days and has about half the mass of Jupiter, or roughly 150 times the mass of the Earth.

The new planet has about twice the radius of the Earth and about seven-and-a-half times its mass, and orbits the star once every two days.

Credit: Trent Schindler, National Science Foundation

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