Laird A. Thompson

Professor of Astronomy


Available to Download:

arXiv:1109.1268-Sept. 2011
An Historical View: The Discovery of Voids in the Galaxy Distribution

arXiv:1301.7331-Jan. 2013
V.M. Slipher and the Development of the Nebular Spectrograph

  • Galaxies & Cosmology (1974-1987): Early in my career I studied clusters of galaxies, galaxy morphology, and did galaxy redshift surveys. While working primarily with collaborator Stephen A. Gregory (U. New Mexico, Prof. Emeritus), I completed a series of deep wide-angle redshift surveys to study the galaxy distribution in and around the richest galaxy clusters in the nearby universe. When mapping the complete 3D galaxy distribution in the vicinity of our initial targets--the Coma cluster and A1367--Gregory and I recognized for the first time large voids in the galaxy distribution ( (Gregory and Thompson 1978. ApJ vol. 222, p. 784). In this 1978 paper we used the term "voids" for the first time in the astronomical literature and posed a challenge to theoretical cosmologists to explain this completely unanticipated structure. For more details on exactly how the discovery was made, I provide two paths. The first is to download the relatively recent (ca. 2011) manuscript shown at the very top of this page. The second path is to go to the explanation in : Voids and Superclusters. The latter is a detailed description that was written ~10 years ago. Each successive redshift survey that has been published since 1978 -- CfA, Las Campanas, 2dF, SDSS -- has served to reconfirm the significance of the beautiful & intricate filamentary structure traced by the large scale distribution of galaxies.

  • Instrumentation (1982-1990): In the early 1980's I began to work on projects aimed at improving the image quality at ground-based telescopes. My first instrument was a microprocessor controlled tip-tilt system called ISIS which was built while I was working at the Institute for Astronomy and was used at Mauna Kea Observatory (Thompson and Ryerson 1983, Proc. SPIE, vol.445, p. 560). Following Foy & Labeyrie's suggestion that laser guide stars might provide the reference source for Adaptive Optics (AO) systems, I initiated the first effort to project a sodium laser guide star into the mesosphere above Mauna Kea Observatory (Thompson and Gardner 1987, Nature, vol. 328, pg. 229). This was followed by 3 years of intense work with Chester Gardner and his students in the Univ. of Illinois Electrical and Computer Engineering Dept. to define many of the pioneering aspects of laser guided AO systems. Unknown to us, a parallel laser guided AO development effort was underway by the U.S. Air Force. How our work helped to trigger the declassification of this Top Secret research is described in the section AO History. In the last 15 years adaptive optics technology has been integrated into every state-of-the-art large ground-based telescope, and it is one of the foundation-technologies of the next generation of giant telescopes. Those of us who pioneered this technology know what a struggle it was to convince conventional astronomers to incorporate AO technology into even a single large telescope.

  • Adaptive Optics Work (1990 - 2009): In 1990 I obtained funds from the National Science Foundation to begin experiments with Rayleigh scattered UV laser guide stars. These experiments with a 35 Watt Excimer laser led directly into my Mt. Wilson laser guided AO system called UnISIS. Unlike AO systems on giant telescopes, UnISIS has an open and flexible design. It is laid out on a large optical bench at the Coude focus of the Mt. Wilson 2.5-m telescope. UnISIS has both laser guide star and natural guide star AO capabilities. Two science cameras allow images to be taken simultaneously at visual and at near-IR wavelengths. On the right is an image of a star taken with UnISIS at 2.12 microns (Ks-band) with a Strehl ratio of 0.67. Following the publication of the 2009 summary paper describing UnISIS (Thompson et al. 2009, Pub. ASP, 121, 498-511), I began to work on other projects. This furlough from AO will end whenever I have the opportunity to relocate to Southern California.
  • Nebular Spectrograph Work (2009 - present): Any astronomical source with a large angular extent and a uniform surface brightness can be detected spectroscopically equally well with a large or a small aperture telescope. The large aperture telescope will provide results with a higher spatial resolution than the small aperture telescope, but both will produce spectra at the same "speed". Although this fact was recognized as early as 1910 by Vesto Slipher, and was eloquently described by Edwin Hubble in his book "The Realm of the Nebulae" (Hubble's tribute to Slipher is in Ch. V), nebular spectrographs generally have not been exploited in modern times. I have recently built a fast fiber-fed nebular spectrograph and have begun to use it at Mt. Laguna Observatory, the only major observatory in California that is not compromised by light pollution. I have placed 14 optical fibers (in a so-called "Integral Field Unit") at the focal plane of a 0.25-m telescope to feed light into the spectrograph. The first results of this research are briefly described here: Nebular Spectrograph.

Postdocs Past & Present Grad Students Past & Present Other Links
Paul Eskridge 1987-1989 Christopher Neyman 2002 Contact Information
Peter McCullough 1993-1995 Michelle Griffin 2003 Teaching
Robert Gruendl 2002-2004 Samuel Crawford Academic Biographical Information
Abhijit Chakraborty 2004-2006   Personal Highlights

Last Updated: September 2, 2013