So Far Away, So Close to Home

UC researchers blasted into headlines this month when they and other researchers revealed their discovery of the most Earth-like extrasolar planet yet, igniting interest in both the public and the scientific community. Scientists say the discovery could be a step in answering the ongoing question of whether there is life on other planets.

Researchers from UC Berkeley, the Carnegie Institution of Washington, UC Santa Cruz and NASA's Ames Research Center used recently improved technology at WM Keck Observatory in Hawaii to detect the planet after first spotting signs of its existence three years ago.

The smallest extrasolar planet ever detected by astronomers, this "super-Earth" is about 7.5 times as massive as Earth, with a radius about twice as large. The discoverers also believe it may be the first known extrasolar, rocky, terrestrial planet that orbits around a normal star, as ours does around the sun.

"You need a rocky planet for there to be life-because, after all, it's a rocky planet that can harbor a lake ... in which the organic chemistry and biochemistry of life could get kick-started," said UC Berkeley astronomy professor Geoffrey Marcy, who lead the team that discovered the planet.

Indeed, the discovery may lead to new theories on planet formation and may allow scientists to study the physical and geological characteristics of planets that could provide a habitat suitable for life.

"Already I'm receiving e-mails from theoretical physicists developing theories for the formation of rocky planets...(and) e-mails from theoreticians trying to build theoretical models of atmospheres," Marcy said.

Knowing more about rocky planets such as these could provide more details about the formation of the solar system.

According to Marcy, scientists are especially interested in whether a new star's orbiting planets are Earth-like and rocky or gaseous like Jupiter or Saturn-or whether planets form at all.

"With this discovery, we have the first and clearest sense that smallish rocky planets like Earth are common," he said.

Theorists who study the composition of planets are curious to know what the planet is like inside and out. If the new planet is indeed made mostly of rock, scientists can begin to consider whether it can hold down an atmosphere, and ultimately if such a planet is hospitable to life, said Eugene Chiang, an associate professor in the UC Berkeley departments of astronomy, and earth and planetary sciences who was not directly involved in the discovery.

More information about the composition of rocky planets could also tell scientists whether a magnetic field, which protects living beings from radiation, could be generated on the planet.

To create a magnetic field, a planet needs to be made of metal and liquid, according to Michael Manga, an associate professor in the UC Berkeley department of earth and planetary Science who was not involved in the discovery.

The larger the planet, the more difficult it may be to generate one, he said.

"It could be really quite boring-it could be nothing is going on on those planets. They might have an atmosphere and storms, but geologically it could be dead," Manga said.

Marcy and his team of researchers presented their findings to the National Science Foundation in a press conference on June 13.

Further improvements to the telescope at the observatory-including a new digital camera-and new forays into space through NASA's three new space missions, could rapidly reveal more Earth-like planets.

Marcy believes that there may be billions or even hundreds of billions of rocky planets in the Milky Way Galaxy.

According to researchers, the discovery of more of such planets could provide more data to be analyzed by scientists from an increasing number of fields, including physicists and astrobiologists. Astrobiology is a field in which scientists seek to determine what constitutes a habitable planet.

"Rather than just having, say, geologists ... you have all these astronomers and physicists thinking about these types of problems in much more detail than they used to," Manga said.

According to Marcy, the real goal in discovering new planets lies in the curiosity of both scientists and nonscientists.

"The search for life in the universe is certainly a profound quest," Marcy said. "I think ultimately we'd like to know: Are we alone in the vast darkness of the universe-are we humans alone?"

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