Palomar Testbed Interferometer

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Palomar Testbed Interferometer
PTI is located atop Palomar Mountain, next to the large white dome of the historic 5 m Hale Telescope.
PTI on Palomar Mountain, next to the Hale Telescope
Location(s) Palomar Mountain
Coordinates 33°21′26″N 116°51′51″W / 33.3571°N 116.8641°W / 33.3571; -116.8641
Organisation Caltech and JPL
Wavelength Near infrared
First light 1995
Telescope style Interferometer
Diameter 110 m
Secondary diameter 0.4 m

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]

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.[citation needed]

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[edit]


  1. ^ M. Shao, et al. (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/0502250Freely accessible. Bibcode:2005ApJ...627..464B. doi:10.1086/430058. Retrieved 2012-01-09. 
  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:0811.4239Freely accessible. 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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