Alpha Centauri should harbor detectable, Earth-like planets, according
to new study by UC Santa Cruz astronomers

For Immediate Release

SANTA CRUZ, CA--A rocky planet similar to Earth may be orbiting one of
our nearest stellar neighbors and could be detected using existing
techniques, according to a new study led by astronomers at the
University of California, Santa Cruz.

The closest stars to our Sun are in the three-star system called Alpha
Centauri, a popular destination for interstellar travel in works of
science fiction. UCSC graduate student Javiera Guedes used computer
simulations of planet formation to show that terrestrial planets are
likely to have formed around the star Alpha Centauri B and to be
orbiting in the "habitable zone" where liquid water can exist on the
planet's surface. The researchers then showed that such planets could
be observed using a dedicated telescope.

"If they exist, we can observe them," said Guedes, who is the first
author of a paper describing the new findings. The paper has been
accepted for publication by the Astrophysical Journal.

Coauthor Gregory Laughlin, professor of astronomy and astrophysics at
UCSC, said a number of factors converge to make Alpha Centauri B an
excellent candidate for finding terrestrial planets. The Doppler
detection method, which has revealed the majority of the 228 known
extrasolar planets, measures shifts in the light from a star to detect
the tiny wobble induced by the gravitational tug of an orbiting
planet. Factors that favor the use of this technique for Alpha
Centauri B include the brightness of the star and its position in the
sky, which gives it a long period of observability each year from the
Southern Hemisphere, Laughlin said.

Detecting small, rocky planets the size of Earth is challenging,
however, because they induce a relatively small wobble in their host
stars. According to Laughlin, five years of observations using a
dedicated telescope would be needed to detect an Earth-like planet
around Alpha Centauri B.

Coauthor Debra Fischer of San Francisco State University is leading an
observational program to intensively monitor Alpha Centauri A and B
using the 1.5-meter telescope at the Cerro Tololo Inter-American
Observatory in Chile. The researchers hope to detect real planets
similar to the ones that emerged in the computer simulations.

"I think the planets are there, and it's worth a try to have a look,"
Laughlin said.

To study planet formation around Alpha Centauri B, the team ran
repeated computer simulations, evolving the system for the equivalent
of 200 million years each time. Because of variations in the initial
conditions, each simulation led to the formation of a different
planetary system. In every case, however, a system of multiple planets
evolved with at least one planet about the size of Earth. In many
cases, the simulated planets had orbits lying within the habitable
zone of the star.

In addition to Guedes, Laughlin, and Fischer, the authors of the paper
include UCSC postdoctoral researcher Eugenio Rivera and graduate
student Erica Davis, and Elisa Quintana of the SETI Institute. This
research was supported by NASA and the National Science Foundation.

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Note to reporters: You may contact Guedes at 1-831-459-5722 or
javiera@ucolick.org; Laughlin at 1-831-459-3208 or
laughlin@ucolick.org; and Fischer at 1-415-338-1697 or
fischer@stars.sfsu.edu.