70 Virginis Solar System, solar system made up of a star, 70 Virginis, which is similar to the sun, and one known planet orbiting the star. The solar system is located 59 light-years from the earth in the constellation Virgo. The star 70 Virginis is slightly less massive and slightly cooler than the earth’s sun.

American astronomers Geoffrey Marcy and Paul Butler announced their discovery of the planet that orbits 70 Virginis, called 70 Virginis B, on January 17, 1996. 70 Virginis B is too dim to be visible from the earth, and Marcy and Butler used an indirect method to discover it. As the planet 70 Virginis B orbits the star 70 Virginis, its gravity tugs at the star from different directions. When 70 Virginis B pulls 70 Virginis away from the earth, the star’s light appears to redden slightly (see Redshift). The star’s light becomes slightly bluer when the planet pulls the star toward the earth. The color change is so small that only sensitive instruments can detect it.

70 Virginis B is about 6.5 times more massive than Jupiter and orbits 70 Virginis at an average distance of about 67 million km (about 40 million mi), about 12 times more closely than Jupiter orbits the sun. The planet follows an elliptical, or oval-shaped, orbit around the star. The time that 70 Virginis B takes to orbit its star completely, known as the planet’s year, is equivalent to about four Earth months. The temperature in the planet’s upper atmosphere is estimated to be about 90° C (about 185° F).

Astronomers theorize that 70 Virginis B formed from a disk of dust around its star, the same way planets formed in the earth’s solar system. They think the planet formed about as far from 70 Virginis as Jupiter is from the sun. The 70 Virginis dust disk was more massive than the sun’s, however, so it slowed 70 Virginis B, causing it to spiral in toward its star. The dust disk dissipated by the time 70 Virginis B reached its present distance from the star.