Photocenter Astronomy

Photocenter Astrometry is a technique we are developing (led by Dave Rowe) that obtains the apparent orbit of a very close (small separation) binary not by imaging the two components (they are too close to be resolved with smaller telescopes), but rather by noting the changing position of the photocenter (the position of what appears to be the single star) over time by comparing its position—very accurately—with a hundred or so other stars in the field-of-view. Degenerate binary companions (nearly or actually invisible white dwarf, neutron star, or black holes) may be capable of detection with the photocenter astrometry technique.  The effects of optical distortion, as well as proper motion and parallactic motions must be removed on all the stars in the field. An advanced version of this technique is being developed and evaluated using a 1-meter PlaneWave Instrument telescope at the Naval Precision Optical Interferometer (NPOI), FIRO, BARO, and DIRO observatories. Since these observations are just “regular” images (i.e., not high-speed speckle interferometry), Los Cumbres Observatory (LCO), the Downing PlaneWave Instruments CDK-17 at Sierra Remote Observatory, and other telescopes could be used for the series of observations that need to be made over time to obtain an apparent (scaled down) orbit.

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