Chi Aquilae
Chi Aquilae is a binary star system in the equatorial constellation of Aquila, the eagle. Its name is a Bayer designation that is Latinized from χ Aquilae, and abbreviated Chi Aql or χ Aql. This system is bright enough to be seen with the naked eye at a combined apparent visual magnitude of +5.29. Based upon parallax measurements made during the Hipparcos mission, Chi Aquilae is at a distance of approximately from Earth.
The two components of χ Aquilae can be separated by spectrum and their relative brightness has been measured, but their other properties are uncertain. The cooler component displays an intermediate spectra between a G2 bright giant and a supergiant, and is visually brighter than the hot component, so it is treated as the primary. The hot component has a stellar classification of B5.5V, matching a B-type main-sequence star.
The absolute magnitude of the primary is −2.1, while that of the secondary is −1. However, the brightness difference between a G2 supergiant and a B5.5 dwarf is expected to be larger. It is unclear whether the primary is not a supergiant or the secondary is brighter than a main-sequence star. As of 2004, the secondary is located at an angular separation of 0.418 arcseconds along a position angle of 76.7° from the primary. The separation and position angle are both decreasing.