Second largest planetary system circles binary star 55 Cancri

William Atkins
Wednesday, 07 November 2007 20:29

Science - Space

A fifth planet has been discovered around the star 55 Cancri, making the planetary system that largest known system besides our own solar system with eight planets.        

The binary star 55 Cancri, within the constellation Cancer, is about 41 light-years from our solar system. The system contains a yellow dwarf star (55 Cancri A) similar to the Sun and a red dwarf (55 Cancri B).

The astronomers who announced this newly discovered planet on Tuesday, November 6, 2007, report that three smaller planets orbit closest to the star system. The innermost planet is the smallest, but is still 18 times more massive than Earth. The next two planets steadily increase in size the further out they go. All three circle at distances from 3.5 to 22 million miles (5.6 to 35.4 million kilometers), which is closer than the planet Mercury orbits the Sun.

The newly discovered planet orbits at a distance of about 70 million miles (113 million kilometers).

The outermost and heaviest planet is the largest of the five planets. It is about four times as massive as the planet Jupiter. It orbits at a distance of about 500 million miles (805 million kilometers), just further the distance that Jupiter circles the Sun.

This planetary system is very important to scientists because it closely resembles Earth’s solar system with its four smaller rocky planets nearer the Sun and its four larger planets orbiting further out.

The findings of this fifth new planet are to be reported in The Astrophysical Journal. The atronomers used data from the Lick Observatory, University of California, and the W. M. Keck Observatory in Hawaii.

Leader of the discovery team is Debra Fischer, assistant professor of astronomy at San Francisco State University (California, U.S.A.).

Coauthors are Geoffrey Marcy, Paul Butler, Steven S. Vogt, Greg Laughlin, Jason T. Wright, John A. Johnson, Kathryn M. G. Peek, Gregory W. Henry, David Abouav, Chris McCarthy, and Howard Isaacson. The authors represent the following institutions: San Francisco State University, Carnegie Institution of Washington, University of California—Berkeley, University of California—Santa Cruz, and Tennessee State University,