Delta Andromedae

Delta Andromedae, Latinized from δ Andromedae, is a triple star system in the northern constellation of Andromeda. The system is visible to the naked eye as a point of light with a combined apparent visual magnitude of 3.28. Based upon parallax measurements, it is located at a distance of approximately 105.5 light-years (32.3 parsecs) from the Sun. The system is drifting closer with a radial velocity of −10 km/s.

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of δ Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ι Piscium, ε Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for δ Andromedae itself is 奎宿五 (Kuí Sù wǔ, English: the Fifth Star of Legs.) Apart from its Bayer designation, it was also given the title Delta by Elijah H. Burritt in his star atlas.

This is a long-period spectroscopic binary with an orbital period of approximately 15,000 days (41 years). The primary of the spectroscopic binary, component Aa, has a stellar classification of K3 III, indicating that it is an aging giant star. It most likely evolved from a F-type main sequence star after consuming the hydrogen at its core. The secondary, component Ab, is a relatively faint K-type dwarf, which has been imaged using a stellar coronagraph. The pair have a physical separation of 11.55±0.13 AU. The system has two companions, the closest of which is most likely an orbiting red dwarf of class M3 with a separation of at least 900 astronomical units.

An excess of infrared emission from δ Andromedae suggested that it may be surrounded by a shell of dust. In 2003 it was determined that this is more likely a circumstellar debris disk.