Pi1 Cygni

π1 Cygni (Latinised to Pi1 Cygni, abbreviated Pi1 Cyg, π1 Cyg) is the star's Bayer designation. The designations of the two components as Pi1 Cygni A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). It bore the traditional name Azelfafage, derived from the Arabic al-sulaḥfāh, the tortoise, originally a name for Lyra that was misattributed to a star in Cygnus. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Azelfafage for Pi1 Cygni on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. == Properties ==

Pi1 Cygni has been described as a single-lined spectroscopic binary with a close, circular orbit, having a period of just 26.33 days. However, a 2020 paper finds no radial velocity variations on the timescale of the published orbit. The primary, visible, star is a somewhat evolved B-type subgiant star with a stellar classification of B3 IV. It has an estimated 10 times the mass of the Sun and around 5.6 times the Sun's radius. The star radiates 16,538 times the solar luminosity from its outer atmosphere at an effective temperature of roughly 18,360 K. It is about 25 million years old and is spinning with a projected rotational velocity of 55 km/s. ==References==