Hanbury Brown and his co-workers at Narrabri Observatory in the 1960s.
Its rapid rotation forces the star to be oblate; its equatorial diameter is over 20 percent greater than its polar diameter. Satellite measurements made in 1999 with the Wide Field Infrared Explorer showed that the brightness of Altair fluctuates slightly, varying by just a few thousandths of a magnitude with several different periods less than 2 hours.
Altair was later observed to be flattened by infrared interferometric measurements made by the Palomar Testbed Interferometer in 1999 and 2000.
Altair was later observed to be flattened by infrared interferometric measurements made by the Palomar Testbed Interferometer in 1999 and 2000.
Ciardi and their co-authors in 2001. Theory predicts that, owing to Altair's rapid rotation, its surface gravity and effective temperature should be lower at the equator, making the equator less luminous than the poles.
This phenomenon, known as gravity darkening or the von Zeipel effect, was confirmed for Altair by measurements made by the Navy Prototype Optical Interferometer in 2001, and analyzed by Ohishi et al.
All are much more distant than Altair and not physically associated. ==Notes== ==References== ==External links== Star with Midriff Bulge Eyed by Astronomers, JPL press release, July 25, 2001. Imaging the Surface of Altair, University of Michigan news release detailing the CHARA array direct imaging of the stellar surface in 2007. PIA04204: Altair, NASA.
As a result, it was identified in 2005 as a Delta Scuti variable star.
In 2006 and 2007, J.
Monnier and his coworkers produced an image of Altair's surface from 2006 infrared observations made with the MIRC instrument on the CHARA array interferometer; this was the first time the surface of any main-sequence star, apart from the Sun, had been imaged.
In 2006 and 2007, J.
The false-color image was published in 2007.
All are much more distant than Altair and not physically associated. ==Notes== ==References== ==External links== Star with Midriff Bulge Eyed by Astronomers, JPL press release, July 25, 2001. Imaging the Surface of Altair, University of Michigan news release detailing the CHARA array direct imaging of the stellar surface in 2007. PIA04204: Altair, NASA.
Image of Altair from the Palomar Testbed Interferometer. Altair, SolStation. Secrets of Sun-like star probed, BBC News, June 1, 2007. Astronomers Capture First Images of the Surface Features of Altair, Astromart.com Image of Altair from Aladin. Aquila (constellation) A-type main-sequence stars 4 Aquilae, 53 Aquilae, Alpha 187642 097649 7557 Delta Scuti variables Altair BD+08 4236 G-Cloud Astronomical objects known since antiquity 0768
It is an abbreviation of the Arabic phrase النسر الطائر (the right, first word having forms from Al Nesr, ranging to An-nisr) Al-ta'ir, "the flying (eagle)". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars.
The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Altair for this star.
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