Reporter's Notes: Exoplanets
Artistic rendition of exoplanet Gilese 436 b, created in Celestia
In the past fifteen years, the search for other Earths– and possibly life– outside our own solar system has taken off. As of May 2008, 293 extrasolar planets have been confirmed. Most of these planets are big, gas giants like our own Jupiter but new technology is helping astronomers get closer to finding earth sized planets. To find an extrasolar planet scientists first identify a star and then, using different methods, look to see if there is a planet, or planets, orbiting the star. It’s estimated that at least 10% of sun-like stars have planets.
Once astronomers have found an extrasolar planet, also called an exoplanet, they look to see if it is in the Goldilocks zone. This is an area of space in which a planet is just the right distance from its' parent star so that the surface is neither too hot nor too cold. A habitable temperature means that the planet could possibly host liquid water, an ingredient for life.
A number of exoplanet findings have come from astronomy teams in Switzerland and near San Jose at Lick Observatory. Astronomers at Lick made news in the fall of 2007 when they discovered 55 Cancri. The discovery of the five-planet system came after nearly 20 years of observations. Also in 2007, astronomers with the Geneva Extrasolar Planet Search Program discovered the most earth-like planet ever found. Gilese 581 c lies in the Goldilocks Zone, it's surface temperature ranges from an estimated 32 degrees Fahrenheit to 102 degrees Fahrenheit. The research team that discovered the new planet believes it may have a developed atmosphere and be covered with oceans.
Curious to see how astronomers hunt for extrasolar planets, I took the trip up the long, windy road to the top of Mt. Hamilton. It is a beautiful drive up to the observatory and it's wise to take your time so that you can enjoy the ideal California landscape of rolling hills dotted with oak trees and wildflowers. The 365 sharp curves along the 19 mile road will also slow you down.
At the top of Mt. Hamilton are several white domes dotting the 4,200-foot crestline. From Lick Observatory you can see forever– not just across the vast northern California landscape but out into our own galaxy and beyond. By coincidence, the night I was there astronomer Debra Fischer confirmed five new planets outside our solar system. The discovery was the culmination of five years of watching these specific planets from Lick's 3-meter Shane Telescope. Fischer and her colleague Geoff Marcy will publish their findings soon. These two astronomers are obsessed with looking for exoplanets, they just returned from the Andes mountains in Chile, where they spent day and night for several weeks hunting for planets. But Fischer and Marcy are not the only ones who have caught the exoplanet bug.
Scientists at NASA are nearly ready to launch a bus-sized telescope into space. NASA's Kepler Telescope which will orbit our sun, will be trained on a hundred thousand stars at a time. It may be our best chance yet for finding new life in outer space. The telescope is scheduled to launch in February. Kepler will find planets by looking for tiny dips in the brightness of a star caused by planetary transits.
Make sure to check out our photo set on Flickr which includes: photos of Lick Observatory; the Kepler testbed at NASA Ames in Mountain View; the Kepler spacecraft assembly in Boulder, Colorado; and artists' renditions of exoplanets discussed in this report.You can also hear our radio story on the search for exoplanets, watch the Planet Hunters TV story online and find additional links and resources.
The radio report on extrasolar planets has several errors.
The report made it sound as though Bay Area astronomers discovered the first extrasolar planets. They did not.
The first extrasolar planets were discovered in 1991, not 1995, and the discovery was made by two astronomers outside California: Alex Wolszczan and Dale Frail. They found two planets in 1991 around a pulsar named PSR B1257+12. A third planet was found around this pulsar in 1993. This work is thoroughly and colorfully documented in Ken Croswell's extrasolar planet book Planet Quest. Wolszczan and Frail published their work in Nature, volume 355, page 145.
Second, the first extrasolar planet discovered around a star like the Sun was found by Swiss astronomers Michel Mayor and Didier Queloz, who are also far beyond California. Their story is again told in Croswell's book, and their paper appears in Nature, volume 378, page 355.
There was a brief mention of Switzerland in the radio report, but no one listening would have guessed the Swiss actually came first with regard to the discovery of an extrasolar planet around a Sunlike star.
And the introduction to the report, about Pluto, was misleading. Contrary to media reports, astronomers have reached no consensus about Pluto's planetary status. A few months ago a conference was held on the definition of a planet. The upshot: "Scientists Debate Planet Definition and Agree to Disagree." Google that sentence and you'll see a report expressing various opinions about Pluto.
Quest is No. CA-centric so the emphasis on the Lick work is understandable. The nationalism in "found a planet" goes as far back as Neptune! That time it was France and Britain.
The Swiss efforts are well recorded and well understood in the scientific and amateur astronomy circles. Trefil, "Other Worlds" (and NPR science advisor), gives appropriate credit. Swiss indeed provided the kick for the No. CA groups to publish their confirming and new planet findings.
The IAU definitions are also clear - Ceres is now again a 'planet' although a "dwarf planet" after being demoted in the late 1800's to an asteroid. Pluto is now demoted to "dwarf planet". And those big ice-balls past Pluto? TNOs?
-Berkeley Astronomy Dept. alumni, former Lick staff, and college friend of a planet finder-