VY Canis Majoris (VY CMa) is a red hypergiant star located in the constellation Canis Major. At between 1800 and 2100 solar radii (8.4–9.8 astronomical units, 2.7 billion km across or 1.7 billion miles) across, it is currently the largest known star and also one of the most luminous known. It is located about 1.5 kiloparsecs (4,900 light years, 4.6×1016 km or 2.9×1016 mi) away from Earth. Unlike most hypergiant stars, which occur in either binary or multiple star systems, VY CMa is a single star. It is categorized as a semiregular variable and has an estimated period of 2000 days.