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The one constant in the Universe: StarDate magazine

The Texas Connection
Finding Earth-Like Planets
Most of the planets discovered outside our own solar system are behemoths -- worlds that are at least as massive as Jupiter, the solar system's giant.

A planet discovered by a team of astronomers led by Barbara McArthur, however, is a relative lightweight -- and perhaps a step toward detecting worlds as small as Earth. The planet orbits the star known as Rho 1 Cancri or 55 Cancri, and is the fourth planet discovered in the system.

Artist's concept of a possible Neptune-mass planet orbiting Rho 1 Cancri.

Artist's concept of a possible Neptune-mass planet orbiting Rho 1 Cancri.

Unlike the others in the system, which are as massive as Jupiter or even bigger, this planet probably is only around 18 times as massive as Earth -- a fraction of Jupiter's mass. Also unlike the others, it probably is rocky, and not a ball of gas like Jupiter. The planet was discovered with the Hobby-Eberly Telescope at McDonald Observatory.

This document was last modified: October 19 2009.

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