New approach for detecting planets in closest neighboring star system: study

LOS ANGELES, Dec. 18 (Xinhua) -- A international research team has taken a fresh look at our closest neighboring system, Alpha Centauri star system, and found new ways to narrow the search for habitable planets there.

According to a study, published in the Astronomical Journal, there may be small, Earth-like planets in Alpha Centauri that have been overlooked. Meanwhile, the study ruled out the existence of a number of larger planets in the system that had popped up in previous models.

"The universe has told us the most common types of planets are small planets, and our study shows these are exactly the ones that are most likely to be orbiting Alpha Centauri A and B," Yale professor Debra Fischer, a leading expert on exoplanets who has devoted decades of research to the search for an Earth analog, was quoted as saying in a news release.

The the nearby Alpha Centauri system has three stars: Centauri A, Centauri B, and Proxima Centauri. Last year, the discovery of an Earth-like planet orbiting Proxima Centauri set off a new wave of scientific and public interest in the system.

Because Alpha Centauri, located 1.3 parsecs (24.9 trillion miles) from Earth, is so close, it is "our first stop outside our solar system," Fischer said. "There's almost certain to be small, rocky planets around Alpha Centauri A and B."

The findings are based on data coming in from a new wave of more advanced spectrographic instruments at observatories located in Chile: CHIRON, a spectrograph built by Fischer's team; HARPS, built by a team from Geneva; and UVES, part of the Very Large Telescope Array.

First author of the study Lily Zhao, Yale graduate student, determined that for Alpha Centauri A, there might still be orbiting planets that are smaller than 50 Earth masses. For Alpha Centauri B there might be orbiting planets than are smaller than 8 Earth masses; for Proxima Centauri, there might be orbiting planets that are less than one-half of Earth's mass.

In addition, the study eliminated the possibility of a number of larger planets. Zhao said this takes away the possibility of Jupiter-sized planets causing asteroids that might hit or change the orbits of smaller, Earth-like planets. Enditem