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August 03, 2010

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That habitable planet might not be so far off

March 10, 2008
Courtesy U. California, Santa Cruz
and World Science staff

An Earth-like, hab­it­a­ble plan­et may be in our stel­lar neigh­bor­hood, and could be found with a ded­i­cat­ed tel­e­scope, new com­put­er sim­ula­t­ions sug­gest.

Astro­nom­ers have long been looking for potentially ha­bi­table planets, and one team fi­nal­ly re­ported a can­di­date pla­ne­tary sys­tem last year. But no place where re­search­ers have pinned their hopes is nearly as close where the new study points.

The Al­pha Cen­tau­ri tri­ple stel­lar sys­tem is our clos­est neigh­bour in space. It lies 4.36 light-years away in the di­rec­tion of the south­ern con­stel­la­tion Cen­tau­rus. In the above pho­to, the two brighter stars of the sys­tem ap­pear as merged to­geth­er due to their lu­mi­nos­i­ty and prox­im­i­ty. The small ar­row at low­er right in­di­cates the lo­ca­tion of the third, dim star, Prox­i­ma Cen­tau­ri. (Cred­it: 1-Meter Schmidt Tel­e­scope, ESO)

An Earth-like, habitable planet may be in our stellar neighborhood, and could be found with a dedicated telescope, new computer simulations suggest. The nearest stars to our Sun are in the three-star system called Alpha Centauri—a popular travel destination in science fiction, though it’s unlikely humans could get there anytime soon. Using simulations based on current planet-formation theories, researchers concluded that Earth-like planets should have formed around one member of this system, the star Alpha Centauri B. One of these, they added, could well be orbiting in the star’s “habitable zone,” a region suitably warm for liquid water to exist on a planet surface. “If they exist, we can observe them,” said Javiera Guedes, a graduate student at the University of California, Santa Cruz. Guedes is first author of a paper detailing the findings, accepted for publication by the research publication Astrophysical Journal. The investigators said they ran the re-enactments repeatedly with different starting assumptions, and got at least one Earth-sized planet each time, and in the habitable zone much of the time. Most of the 228 planets discovered outside our solar system so far have been found through the Doppler method, which analyzes starlight to detect tiny wobbles in a star due to a planet’s gravitational pull. But it’s challenging to detect rocky, Earth-sized planets because they induce only a tiny wobble. But astronomer Gregory Laughlin of the university, a co-author of the report, said several factors make Alpha Centauri B an excellent candidate for finding terrestrial planets. These 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 it would take five years of watching using a dedicated telescope to detect an Earth-like planet around Alpha Centauri B. Co-author 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. Visiting any hypothetical aliens in Alpha Centauri would not be an easy project, despite the stars’ relative proximity of 4.35 light-years. A light-year is the distance light travels in a year, so it would take about four years for light to get there from here. Our fastest spacecrafts used to date would take about 60,000 years to go there, although some scientists predict new technology could reduce that time considerably.