Dr. Gunn led the Sloan Digital Sky Survey, which produced a three-dimensional digital cosmic map encompassing a broad region. He played a leading role in the project, including planning, instrument development, and data analysis, and contributed to the elucidation of the evolutionary history of the universe. He also published many pioneering astrophysical theories. Through these achievements, he has provided us a significant understanding of the universe.
Dr. James Gunn designed the Sloan Digital Sky Survey (SDSS) project, which produced a three-dimensional digital cosmic map through a survey of a broad region of the universe. He assumed a leading role in nearly all areas—including the development of observation instruments, data analysis software, a framework for data publication, and scientific analysis. Observational cosmology has developed along two strategies: one is to observe distant (past) individual celestial bodies through the Hubble Space Telescope and large ground-based telescopes, and the other is to observe many celestial bodies in a broad region to deduce an overview of the universe. Dr. Gunn led the SDSS, which went on to be a representative project for the latter strategy. It produced an enormous amount of precise observational data and innovatively deepened our understanding of cosmic history and the properties of various celestial bodies. Furthermore, it successfully determined the parameters of the expanding universe with unprecedented precision.
Dr. Gunn proposed the SDSS project (1) by designing a 2.5-m wide-field telescope that served as the backbone of the project (2), a sensitive ultra-large mosaic CCD camera (3), and a multi-object spectrograph that enabled the simultaneous measurement of 640 celestial bodies (4). This project commenced in 1992 with seven U.S. institutions and a Japanese group, and observations began in 2000. As observational data and research accomplishments were published, the number of participating institutions increased to 25. By 2009, 230 million celestial bodies were cataloged, and the spectra of 930,000 galaxies, 120,000 quasars, and 460,000 stars were obtained (5). Through the publication of the SDSS astronomical catalog, including a homogeneous and overwhelming amount of information, many discoveries were made. Thus, the SDSS is now regarded as the most successful project in the history of observational astronomy.
Major scientific achievements of the SDSS include the production of a three-dimensional cosmic map of galaxies covering one-fourth of the sky as far as 2.5 billion light years away; the elucidation of the large-scale structure of the universe (6–8); and discoveries of numerous distant quasars (9), gravitational lensing phenomena (10), and new populations of low-temperature brown dwarfs (11).
The data on galaxy distribution obtained by the SDSS were combined with data on the temperature fluctuation of cosmic microwave background radiation to reveal that the fraction of normal matter in the universe is less than 5%, whereas the rest of the universe is composed of dark matter (approximately 25%) and dark energy (approximately 70%) (6). Today, this finding has been established as a standard model of the universe. For further investigation of dark matter and dark energy and elucidation of the origin of the structure of the universe, the SDSS provides fundamental data to the cutting-edge research that connects particle physics and cosmology.
Dr. Gunn not only led the SDSS, but also published many pioneering astrophysical theories (12), including a method that determines the degree of ionization of the past universe (13). He has also made significant contributions to the development of various innovative observation instruments. As modern astronomy research has progressively become fragmented, Dr. Gunn is a rare astronomer who has produced outstanding achievements in theory, observation, and instrument development. Dr. Gunn is trusted by researchers and engineers worldwide owing to his leadership in a large-scale survey that led to a breakthrough in astronomical observations and made a significant contribution to our understanding of the universe. He is, without a doubt, a worthy recipient of the Kyoto Prize.
(1) York DG, et al. (2000) The Sloan Digital Sky Survey: technical summary. The Astronomical Journal120: 1579–1587
(2) Gunn JE, et al. (1998) The 2.5 m telescope of the Sloan Digital Sky Survey. The Astronomical Journal131: 2332–2359.
(3) Gunn JE, et al. (1998) The Sloan Digital Sky Survey photometric camera. The Astronomical Journal116: 3040–3081.
(4) Smee SA, et al. (2013) The multi-object, fiber-fed, spectrographs for the Sloan Digital Sky Survey and the baryon oscillation spectroscopic survey. The Astronomical Journal 146: 32.
(5) Abazajian KN, et al. (2009) The seventh data release of the Sloan Digital Sky Survey. TheAstrophysical Journal Supplement Series182: 543–558.
(6) Tegmark M, et al. (2004) Cosmological parameters from SDSS and WMAP. Physical Review D69: 103501.
(7) Eisenstein DJ, et al. (2005) Detection of the baryon acoustic peak in the large-scale correlation function of SDSS luminous red galaxies. The Astrophysical Journal633: 560–574.
(8) Becker RH, et al. (2001) Evidence for reionization at z~6: detection of a Gunn-Peterson trough in a z=6.28 quasar. The Astronomical Journal122: 2850–2857.
(9) Fan X, et al. (2001) High-redshift quasars found in Sloan Digital Sky Survey commissioning data. IV. Luminosity function from the fall equatorial stripe sample. The Astronomical Journal121: 54–65.
(10) Oguri M, et al. (2006) The Sloan Digital Sky Survey quasar lens search. I. Candidate selection algorithm. The Astronomical Journal132: 999–1013.
(11) Hawley SL, et al. (2002) Characterization of M, L, and T dwarfs in the Sloan Digital Sky Survey. The Astronomical Journal123: 3409–3427.
(12) Ostriker JP & Gunn JE (1969) On the nature of pulsars. I. Theory. The Astrophysical Journal157: 1395–1418.
(13) Gunn JE & Peterson BA (1965) On the density of neutral hydrogen in intergalactic space. The Astrophysical Journal142: 1633–1641.