Palomar Testbed Interferometer

The Palomar Testbed Interferometer (PTI) was a near infrared, long-baseline stellar interferometer located at Palomar Observatory in north San Diego County, California, United States. It was built by Caltech and the Jet Propulsion Laboratory and was intended to serve as a testbed for developing interferometric techniques to be used at the Keck Interferometer. It began operations in 1995 and achieved routine operations in 1998, producing more than 50 refereed papers in a variety of scientific journals covering topics from high precision astrometry[1] to stellar masses,[2] stellar diameters and shapes.[3] PTI concluded operations in 2008 and has since been dismantled.[4]

Palomar Testbed Interferometer
PTI on Palomar Mountain, next to the Hale Telescope
Location(s)San Diego County, California
Coordinates33°21′26″N 116°51′50″W
OrganizationCalifornia Institute of Technology
Jet Propulsion Laboratory 
First lightJuly 1995 
DecommissionedDecember 2008 
Telescope styleastronomical interferometer
optical telescope 
Number of telescopes3 
Diameter0.4 m (1 ft 4 in)
Location of Palomar Testbed Interferometer

PTI was notable for being equipped with a "dual-star" system, making it possible to simultaneously observe pairs of stars; this cancels some of the atmospheric effects of astronomical seeing and makes very high precision measurements possible.

A groundbreaking study with the Palomar Testbed Interferometer revealed that the star Altair is not spherical, but is rather flattened at the poles due to its high rate of rotation.[5]

See also

References
  1. M. Shao, et al. (PTI Collaboration) (1999). "Differential Astrometry of the 61 Cygni System with the Palomar Testbed Interferometer". Bulletin of the American Astronomical Society. 31: 1504. Bibcode:1999AAS...195.8714S.
  2. Boden, Andrew F.; Torres, Guillermo; Hummel, Christian A. (1 July 2005). "Testing Stellar Models with an Improved Physical Orbit for 12 Bootis". The Astrophysical Journal. 627 (1): 464–476. arXiv:astro-ph/0502250. Bibcode:2005ApJ...627..464B. doi:10.1086/430058.
  3. van Belle, G. T.; Creech-Eakman, M. J.; Hart, A. (21 April 2009). "Supergiant temperatures and linear radii from near-infrared interferometry". Monthly Notices of the Royal Astronomical Society. 394 (4): 1925–1935. arXiv:0811.4239. Bibcode:2009MNRAS.394.1925V. doi:10.1111/j.1365-2966.2008.14146.x.
  4. "Caltech Astronomy - The Palomar Testbed Interferometer (PTI)". Caltech Astronomy. Retrieved 2014-12-09.
  5. van Belle, Gerard T.; Ciardi, David R.; Thompson, Robert R.; Akeson, Rachel L.; Lada, Elizabeth A. (1 October 2001). "Altair's Oblateness and Rotation Velocity from Long‐Baseline Interferometry". The Astrophysical Journal. 559 (2): 1155–1164. Bibcode:2001ApJ...559.1155V. doi:10.1086/322340.


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