A team of astronomers, including SF State faculty and alumni, announced on Aug. 31 the discovery of two new planets, one orbiting the star Gliese 436 and the other circling Rho Cancri.

The discovery of the new planets, both approximately the size of Neptune, is the first time astronomers have seen extra-solar planets smaller than Saturn.

One of the new finds also marks the discovery of the first-known star system with four planets orbiting a star other than our own.

Dr. Chris McCarthy, an astronomer with SF State’s astronomy and Physics department, said he and his colleagues are pleased with their latest find.

“Yes, there’s been a very exciting discovery,” McCarthy said. “Previously we’d only been able to find planets as big as Jupiter. It’s easier to find these large planets.

“Currently, no Earth-bound observatory has the capability of detecting an Earth-type planet – yet. We’re trying to work our way down to that level of detectability so this is an important step in that goal.”

The planet hunting team, which includes former SF State astronomy professor Geoff Marcy, current SF State astronomer Dr. Debra Fischer and alumni Paul Butler, used the W.M. Keck telescope in Hawaii and telescopes at Lick Observatory to find the new planets.

The first of the two new planets orbits an M-type dwarf star. The second new planet revolves around a yellow dwarf star, similar to our sun. Dwarf stars are typically small, low mass objects and are the most common type of stars in the universe.

Because astronomers have already discovered three other planets orbiting Rho Cancri, the new find makes it the first quintuple, or 4-planet, star system ever seen.

In a press release from the National Science Foundation, Marcy described the difficulty of finding a planet around a red dwarf star like Gliese 436.

“They’re hard because they’re so dim,” Marcy said. “Only with the largest telescopes in the world – the Keck for example – can you do the Doppler technique on them, and then only with the very nearest.”

McCarthy said the Doppler method for finding extra-solar planets is similar to a traffic cop using radar to catch a speeding driver.

“Instead of speeding cars, we measure speeding stars,” he said.

Back in 1995, SF State astronomers barely missed discovering the very first extra-solar planet ever found. A Swiss-led team announced the discovery of a planet orbiting the star 51 Pegasi just days before SF State’s team confirmed their first planetary find.

So far, the SF State team, known as the California & Carnegie Planet Search, still leads the race for the most number of extra-solar planets detected with over 80 discoveries to their credit.

“It’s important to understand the makeup of the cosmos,” McCarthy said. “We’d like to know how we fit in. Is Earth typical? Are there many or few (Earth-like planets)?”

McCarthy said he believes that SIM will detect an Earth-sized planet sometime before 2010. In a thesis he wrote in the early ‘90s, he predicted that astronomers would find the first extra solar planet within five years.

“Someday we’ll find a planet like Earth,” he said.