Geoffrey Marcy (right) and Paul Butler at Lick Observatory, where they
began their
phenomenal journey of discovery in 1987 (photo: Mickey Pfleger)
Alumnus Geoffrey Marcy (Ph.D., astronomy and astrophysics, '82) is part of a team recognized worldwide for its success in finding planets around sunlike stars in other solar systems.
When Geoffrey Marcy was thirteen years old, his parents bought him a poster of Earth's solar system and, later, a telescope. At fourteen, he watched Neil Armstrong's historic walk on the moon.
Marcy, 42, took his own leap for mankind a year ago when he and fellow astronomer Paul Butler discovered two distant planets located between 40 and 70 light-years from Earth.
The planets--70 Virginis b in the constellation Virgo and 47 Ursae Majoris b in the Big Dipper--were only the second and third to be discovered outside our solar system.
Although the severe climates of these two planets make them unlikely harbors for organic life, their existence implies that the Milky Way galaxy, with more than 100 billion stars, may play host to other, more hospitable worlds.
Since discovering Ursae Majoris b and Virginis b, Marcy and Butler have found four more planets. Their discoveries have earned them recognition as the greatest team of planet hunters in the world and generated comparisons to Copernicus and Columbus.
A Distinguished University Professor at San Francisco State University and an adjunct professor at UC Berkeley, Marcy embarked on his planet search in the early 1980s while a fellow of the Carnegie Institution.
"The discovery of other planets was something I had pondered when I was a kid," said Marcy. "As a researcher, I wanted to tackle a question that many children ask: 'Are there planets around the stars I see at night?'"
Starting in 1987, Marcy and Butler used the University of California's Lick Observatory east of San Jose to record measurements of the light spectra--the light arranged by its numerous colors--emanating from 120 stars similar in size to our sun.
Because distant planets are far too dim to be seen against the glare of their parent stars, the team looked for almost-infinitesimal changes in the stars' light spectra, called Doppler shifts, that can indicate the presence of a planet.
Scientists know that gravity exerted by an orbiting planet will cause a star to wobble ever so slightly in its path across the sky. These movements are marked by a shift toward blue or red in the star's light spectrum. Larger planets, with their higher gravity, cause a more severe wobble than do their smaller counterparts, creating more distinct changes in color.
Until recently, no instrument was precise enough to discern these color shifts, even for the largest planets. A major refurbishment of the Lick spectrograph carried out by UC Santa Cruz professor of astronomy and astrophysics Steven Vogt--Marcy's Ph.D. thesis adviser--made seeing the color shift possible. In addition to the improved spectrograph, the planet hunters made use of powerful computers and an innovative and elaborate computer program they developed to weed out errors in the data.
Most of the planets Marcy and Butler have found so far in their sample of 120 stars are similar in size to Jupiter. Two of them, Rho Cancri and Upsilon Andromedae, are thought to be a little less massive. With the refurbished spectrograph at Lick, Marcy is monitoring the same stars for evidence of planets as small as Saturn in size.
The pair have also expanded their search to 350 additional stars using the world's largest telescope at the W. M. Keck Observatory in Hawaii; there, they are looking for planets as small as Uranus and Neptune.
This year, UCSC awarded Marcy the Alumni Achievement Award, the highest
honor the Alumni Association bestows on a graduate of UCSC. More information
on the planet search can be found at Marcy and Butler's "Searching
for Extrasolar Planets" World Wide Web page at http://cannon.sfsu.edu/~williams/planetsearch/
planetsearch.html.
--Francine Tyler