New Super-Earth's Orbit Sun-Like Stars

Earth-Like Planets Orbit Sun-Like Stars

An international team of planet hunters has discovered as many as six low-mass planets, around two nearby Sun-like stars, including two "super-Earths" with masses 5 and 7.5 times the mass of Earth. The researchers, led by Steven Vogt of the University of California, Santa Cruz, and Paul Butler of the Carnegie Institution of Washington, said the two "super-Earths" are the first ones found around Sun-like stars.

The team found the new planet systems by combining data gathered at the W. M. Keck Observatory in Hawaii and the Anglo-Australian Telescope (AAT) in New South Wales, Australia. Three of the new planets orbit the bright star 61 Virginis, which can be seen with the naked eye. Astronomers and astrobiologists have long been fascinated with this particular star, which is only 28 light-years away. Among hundreds of our nearest stellar neighbors, 61 Virginis stands out as being the most nearly similar to the Sun in terms of age, mass, and other essential properties.

The second new system found by the team features a 7.5-Earth-mass planet orbiting HD 1461, another near-perfect twin of the Sun located 76 light-years away. At least one and possibly two additional planets also orbit the star. Lying in the constellation Cetus, HD 1461 can be seen with the naked eye in the early evening under good dark-sky conditions. The 7.5-Earth-mass planet, assigned the name HD 1461b, has a mass nearly midway between the masses of Earth and Uranus. The researchers said they cannot tell yet if HD 1461b is a scaled-up version of Earth, composed largely of rock and iron, or whether, like Uranus and Neptune, it is composed mostly of water. In the past year, it has become evident that planets orbiting the Sun's nearest neighbors are extremely common.

According to Butler, current indications are that one-half of nearby stars have a detectable planet with mass equal to or less than Neptune's. Due to improvements in equipment and observing techniques, these ground-based methods are now capable of finding Earth-mass objects around nearby stars, according to team member Gregory Laughlin, professor of astronomy and astrophysics at UCSC. This could mean that there is inhabitable planets in the universe that are very similar to Earth.