Variable binary star system in the constellation Aquila
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! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000      Equinox J2000
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | U−B 
! style="text-align:left" | B−V 
! style="text-align:left" | Variable type
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U Aquilae is a binary star system in the constellation Aquila, Located approximately away from Earth.
The primary star (component A) is a yellow supergiant with a radius of 55 R☉ and a luminosity of 2,570 L☉. The secondary (component B) is a blue main-sequence star, twice the mass of the sun and around thirty times more luminous. It is hotter than the primary star at 9,300 K, but much smaller and fainter. The two stars orbit every five years and their separation varies from five to seven astronomical units in a mildly eccentric orbit.
Discovery of the variability of U Aquilae was announced by Edwin F. Sawyer in 1886. In his announcement, he called the star 50 Aquilae, which is its designation in "Uranometria Argentina". Sawyer had begun observing the star in late 1882, and had derived a period of "about one week". It was listed with its variable star designation, U Aquilae, in Annie Jump Cannon's 1907 "Second Catalogue of Variable Stars".
U Aquilae A is a classical Cepheid variable star, ranging between magnitudes 6.08 and 6.86 over a period of 7.02 days. It is an evolved star which has exhausted its core hydrogen and is now fusing helium into carbon.
References.
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