Porrima — おとめの二重星

Porrima, Gamma Virginis, is one of the most famous visual binaries in the sky — a pair of nearly identical F0 V dwarfs in a highly eccentric 169-year orbit. Both stars shine at magnitude 3.5, giving a combined magnitude of 2.7. The system lies just 33 light-years away, making it one of the closest bright visual binaries. Periastron passage in 2005 brought the pair to within 0.4 arcseconds — inseparable even in large amateur telescopes.

In the 2020s the pair has widened to roughly 3-4 arcseconds — comfortable for a 4-inch telescope at 150x. The separation continues to grow, peaking around 2080 before closing again. Both components appear pale yellow-white and nearly equal, making Porrima one of the sky's finest "matched pairs." Find it by following the right-angle formed by Auva, Vindemiatrix, and Spica in southern Virgo. Best observed February through July.

Porrima takes its name from a Roman goddess of prophecy, preserved through medieval Latin astronomy. The binary nature was discovered by Bradley and Pound in 1718, and the orbit was first computed by Sir John Herschel in 1833 — making Porrima one of the first stars whose orbital motion proved that gravity operates beyond our solar system. The IAU formally adopted "Porrima" for Gamma Vir A in 2016.