A $600,000 gift from the Gloria and Kenneth Levy Foundation will help fund an integral part of the Automated Planet Finder now being built at the University of California’s Lick Observatory.
The new telescope will collect starlight on an 8-foot (2.4-meter) primary mirror and direct it into a world-class spectrometer to be named for the Levys. When the instrument begins its work next May, it will devote all its time to searching for the telltale light shifts that indicate a planet orbiting around a distant star. The new spectrometer will bring within reach one of astronomy’s longest-held goals: the discovery of an Earth-sized planet in another solar system.
A spectrometer’s job is to split a pencil-sized beam of starlight into a rainbow of constituent colors and then measure very accurately the positions of dark “absorption lines” in the rainbow. The new instrument marks a pinnacle in the career of veteran spectrometer designer Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz. Vogt’s past designs include the two most successful planet-finding spectrometers in operation today–the high-resolution “HIRES” spectrometer, mounted on the 10-meter Keck I Telescope at the W. M. Keck Observatory in Hawaii, and the Hamilton spectrometer on the 3-meter Shane Telescope at Lick Observatory.
Over his career, Vogt said, “I’ve gathered a lot of knowledge about the right ways to do things, and I’ve poured everything I know into this design.”
Vogt is one of the principal scientists on the California-Carnegie Planet Search team, a group of astronomers who search the skies for extrasolar planets, or planets beyond our solar system. Other members of the group’s science team include Geoffrey Marcy of UC Berkeley, who was Vogt’s first graduate student, Paul Butler of the Carnegie Institution of Washington, and Debra Fischer of San Francisco State University.
“We’re beyond delighted that Ken Levy is going to make this search for other Earths possible,” Marcy said.
The team has an extraordinary record of finding extrasolar planets, having discovered around 140 of the 240 found so far. Most of those planets have been the size of Jupiter or Saturn–roughly 300 times the size of Earth.
“It’s quite remarkable. They’ve opened a brand-new branch of science, the science of extrasolar planets,” said Michael Bolte, director of UC Observatories/Lick Observatory (UCO/Lick). The Automated Planet Finder will set its sights on small, Earth-like planets, ones that orbit their stars at the right distance for water to exist as a liquid and that might feature a rocky surface where water could pool and serve as a cradle of life.
The instrument will check in on 25 stars per night during every clear night of the year, using an intelligent program that decides which stars to watch based on criteria such as sky conditions, the Earth’s position in space, and results from previous observations. Over the next decade, the telescope will study 1,000 nearby stars, all within about 50 light-years.
Finding planets that are trillions of miles away is no small feat. Researchers do it by watching for shifts in the colors emanating from stars. The principle involved is similar to the way a radar gun can measure the speed of a car or a pitcher’s fastball. Astronomers use Doppler shifts in the wavelengths of starlight as evidence that the star is speeding up or slowing down in response to the gravitational tug of an orbiting planet.
“We’re looking for shifts in the spectrum on the focal plane of the spectrometer that are on the order of a thousandth of a pixel,” Vogt said. “And we have to be able to find those shifts and track them from year to year, summer to winter, spring to fall. The shifts we’re looking for amount to a distance of about 80 atoms on the surface of the CCD [camera].”
To be sure a planet is there, scientists must observe the star through several of the planet’s orbits, and that can take six months to several years for the kinds of planets the team hopes to detect. With observational time on the world’s elite telescopes limited to only a few nights in a row for any one project, the team realized their best bet was to build their own.
The Automated Planet Finder telescope is less than a quarter the size–and gathers less than one-sixteenth the light–of the 10-meter Keck Telescopes, the largest optical telescopes currently in use. Vogt said he “bought back” much of the difference with superlative optical components and a new spectrometer design. The result is an efficiency two to four times greater than that of the Keck and other leading telescopes. “Thirty percent of the photons are usable by science,” Vogt said.
To conserve light, Vogt decided to forgo the standard fiberoptic cables that carry telescope light to a spectrometer inside a climate-controlled room. Fiberoptics can squander as much as 30 percent of the light, Vogt said, so he shrank his design enough to bolt it directly onto the telescope. The new spectrometer is the size of a phone booth, he said, compared to previous models that were twice the size of his office.
Vogt surrounded the spectrometer with a steel and magnesium skeleton that passively adjusts its shape as temperatures change, keeping the system’s optics in perfect alignment. The rigid, lightweight frame also keeps the spectrometer from flexing or sagging as the rotating telescope carries the instrument away from the vertical.
Other innovations include silver instead of the standard aluminum mirrors and antireflective lens coatings that Vogt had custom-made at the Lick Optical Laboratory on the UCSC campus. The computer program that makes sense of the spectrometer readings, written by Butler, accounts for everything from Earth’s spin to the way relativity warps starlight as it speeds past the Sun.
Kenneth Levy became interested in the hunt for distant planets after hearing Marcy speak about the project. Later, Marcy and Levy toured the Lick Observatory on Mt. Hamilton, east of San Jose. The two spent an hour examining the optical system that occupies a room nicknamed “the Dungeon” beneath the Shane Telescope.
Levy, whose background is in electrical engineering, “very quickly captured the notion of the extraordinary optical engineering that UCO/Lick does,” Marcy said. “He is a connoisseur of some of the best optical engineering in the world, so we appreciate each other.”
Levy built his career around a pioneering Silicon Valley firm, KLA (now KLA-Tencor), that he founded in the 1970s. He was the firm’s CEO for more than 20 years and served as chairman of the board from 1999 until he retired in 2006. He and his wife, Gloria, are involved in philanthropy through their foundation.
When Levy learned that the Automated Planet Finder would employ an even more sophisticated optical system, albeit one built on the astronomical version of a shoestring, he asked what he could do to help, Marcy said.
Additional funding for the APF has been provided by the U.S. Naval Observatory, NASA, the National Science Foundation, and UCO/Lick.
The Automated Planet Finder will be the seventh major telescope at the Lick Observatory, located on the summit of Mt. Hamilton at an elevation of 4,200 feet. Founded in 1888, Lick remains one of the most productive research observatories in the world. UCO/Lick, headquartered on the UCSC campus, operates the Lick Observatory and is a managing partner of the W. M. Keck Observatory in Hawaii.
Note to reporters: You may contact Vogt at (831) 459-2151 or vogt@ucolick.org, Bolte at (831) 459-2991 or bolte@ucolick.org, and Marcy at (510) 642-1952 or gmarcy@astro.berkeley.edu.
