Stephen A. Shectman
Carnegie Institution for Science
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Primary Section: 12, Astronomy Membership Type:
Member
(elected 2014)
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Biosketch
Stephen Shectman is a staff scientist at Carnegie Observatories in Pasadena, California. Shectman is an observer and an instrumentalist who is known for his work on the large scale structure of the distribution of galaxies in space, on the search for extremely metal-poor stars formed during the earliest epochs of galactic star formation and nucleosynthesis, for the development of sensitive optical instruments and detectors, and for the construction of large telescopes. Shectman was born in New York City in 1949 and grew up on Long Island. He graduated from Yale University in 1969 with a degree in physics and received a PhD in astronomy from the California Institute of Technology in 1973. From 1973 to 1975 Shectman was a postdoctoral scholar in astronomy and a lecturer in physics at the University of Michigan, and joined the staff of the Carnegie Observatories in 1975. From 1985 to 2004 he served as Project Scientist for the Magellan Telescope Project, which led to the construction of two 6.5-meter telescopes at the Las Campanas Observatory in Chile.
Research Interests
Shectman's current research is centered primarily on the search for extrasolar planets by making precise measurements of the periodic variation of the Doppler shift of the parent star, and on the design of instrumentation for large telescopes. Using a temperature-controlled, high-resolution spectrograph installed on the Magellan telescopes in Chile, in conjunction with an iodine absorption cell, Shectman and his collaborators achieve a long-term precision of about 1 meter/sec rms. Such observations require high signal-to-noise ratio and low sytematic error, because the intrinsic FWHM of the absorption lines in stellar spectra is typically about 5 km/s. For comparison a distant observer measuring the Doppler shift of the Sun would measure velocity variations with an amplitude of 12 m/s due the planet Jupiter, while the effect of the Earth at 0.1 m/s would be swamped by noise from intrinsic stellar variations, for example from turbulence in the solar photosphere or from sunspots. Most instruments on large telescopes are built to work in the seeing-limited regime, where the final image size is the result of atmospheric turbulence rather than the diffraction limit of the telescope. In this case the size of optical instruments, for example spectrographs with diffraction gratings, focussing optics and large-area detector arrays, scales directly with the aperture of the telescope. For large and extremely-large telescopes the challenge of building useful instruments with optical elements of practical size becomes acute. Shectman has designed a number of variations of wide-field spectrographs, which can be used to take spectra of many objects in the telescope field of view at the same time, as well as single-object high-resolution spectrographs. Some of these instruments have been implemented for use on the Magellan telescopes in Chile, while others are intended as design studies for the future generation of extremely-large telescopes.
