U Aquilae

U Aquilae

File:UAqlLightCurve.png A visual band light curve for U Aquilae, adapted from Kiss (1998)
Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	6.08 - 6.86
Characteristics
Spectral type	F5-G1 I-II + B9.8V
U−B Template:Engvar	0.70
B−V Template:Engvar	1.10
Variable type	δ Cep
Astrometry
Radial velocity (Rv)	−6.5 km/s
Proper motion (μ)	RA: −0.99 mas/yr Dec.: −9.14 mas/yr
Parallax (π)	3.63±0.96 mas
Distance	614 pc
Absolute magnitude (MV)	−3.68
Orbit
Period (P)	1,856
Semi-major axis (a)	1.311" (6.1 AU)
Eccentricity (e)	0.165
Inclination (i)	74°
Longitude of the node (Ω)	190°
Details
A
Mass	5.7 Template:Solar mass
Radius	55 Template:Solar radius
Luminosity	2,570 Template:Solar luminosity
Surface gravity (log g)	1.3 cgs
Temperature	5,440-6,640 K
Metallicity [Fe/H]	0.17 dex
B
Mass	2.3 Template:Solar mass
Radius	2.1 Template:Solar radius
Temperature	9,300 K
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBAD	data

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 Template:Solar radius and a luminosity of Template:Solar luminosity. 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.