Meeting Information

Exoplanet Searches with PFS and APF

December 18, 2013
American Center for Physics
College Park, MD

Date: Wednesday, 18 December, 2013

Speaker: Dr. R. Paul Butler, DTM – Carnegie Institution of Science

Topic: Exoplanet Searches with PFS and APF

Time and Location: 1:00 pm, with Q&A to follow; in a 1st floor conference room at the American Center for Physics (, 1 Physics Ellipse, College Park, MD — off River Rd., between Kenilworth Ave. and Paint Branch Parkway.

Abstract: Our modern science began with Copernicus speculating that the Earth is a planet and that all the planets orbit the Sun. Bruno followed up by speculating that the Sun is a star, that other stars have planets, and other planets are inhabited by life. For this and other heresies, Bruno was burned at the stake in a public square in Rome in 1600. Astronomy and extrasolar planets were a really hot field at the time.

Over the past 20 years more than a thousand extrasolar planets have been found, first from ground-based precision Doppler and photometric transit surveys, and more recently by the Kepler space mission. We have concentrated on building precise Doppler systems to survey the nearest stars. Our systems at Lick, Keck, AAT, and Magellan have found hundreds of planets, including five of the first six planets, the first Saturn-mass planet, the first Neptune-mass planet, the first terrestrial mass planet, and the first multiple-planet system.

We are currently focusing our attention on new custom built "R4" échelle spectrometers designed for iodine cells, which are yielding 1 m/s accuracy. These spectrometers have a footprint about the size of a ping pong table, allowing for temperature stabilization, yet deliver higher resolution and dispersion than the much larger classic échelle spectrometers, such as the Lick Hamilton, the AAT UCLES, and the Keck HIRES. The two working examples, PFS on the 6.5-m Magellan, and the Levy spectrometer on the 2.4-m APF, cost about US$2M each. They do not use fibers or scrambling, and have throughput of 20 to 30%, a factor of 2 to 4 better than classic échelles. These spectrometers will lead to the discovery of many terrestrial mass and potentially habitable planets over the next decade.

Biography: Paul Butler is currently a staff scientist at the Department of Terrestrial Magnetism of the Carnegie Institution of Science in Washington, D.C. (formerly the Carnegie Institution of Washington). Dr. Butler and his colleagues are pioneers in the search for extrasolar planets. Butler and his associate, Dr. Geoffrey Marcy, developed the most sensitive and widely-used planet-detection technique and have discovered most of the known planets, including the first multiple-planet system, the only planet thus far found to transit a host star, and two sub-Saturn mass planets.

Butler was born in San Diego, California. He earned bachelor’s degrees in physics and chemistry as well as a master’s in physics from San Francisco State University. He received a doctorate in astronomy at the University of Maryland in 1993. In 2001, Butler was awarded the prestigious Henry Draper Medal from the National Academy of Sciences. Other recent honors include being named an American Astronomical Society Centennial Lecturer in 2000 and receiving the inaugural University of Maryland College of Physical Sciences Distinguished Alumnus Award in 2001. Butler served as a research scientist at San Francisco State University and a visiting research fellow at the University of California, Berkeley from 1993 to 1997. From 1997 through 1999 he was a staff astronomer at the Australian Astronomical Observatory (formerly the Anglo-Australian Observatory), where he initiated the Anglo-Australian planet search. Butler’s current work focuses on improving the sensitivity of the precision velocity planet search technique to detect smaller-mass and more-distant planets, and on expanding the ongoing planet survey to all 2,000 nearby Sun-like stars out to about 50 parsecs (150 light-years).