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Proper NameNone
Bayer DesignationPhi Pegasi
Flamsteed Number81 Pegasi
HR (BSC)9036
Right Ascension23h 52m 29s
Declination+19° 7' 13"
Distance468 light years
144 parsecs
MagnitudeApparent: +5.07
Absolute: -0.72
Spectral ClassM2.5IIIb red giant
Optimum VisibilitySeptember / October

A star that falls inside the Square of Pegasus, Phi Pegasi is in the southeastern quadrant of the Square, a matter of some 6.5° from the corner star Algenib. This is a red giant, but at a distance of 468 light years it is barely visible to the naked eye from Earth. Its brightness varies over time, and as it is already on the very edge of naked eye visibility, for some observers the star will at times be too faint to detect.

Imagery provided by Aladin sky atlas

Structurally Phi Pegasi is similar to the more familiar Betelgeuse in Orion, the old and giant red outer shell of a star that has evolved and expanded after consuming its reserves of hydrogen. Also like Betelgeuse, Phi Pegasi is a semiregular variable; it grows brighter and fainter over time, but those shifts do not follow a simple regular pattern.


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