Nova Cygni 1975
In the summer of 1975 Cygnus the Swan sprouted another tail as Nova Cygni 1975 erupted in the night sky. It reached magnitude 1.8 and became brighter than Deneb the brightest star in Cygnus. Nova are common with several discovered each year but most are quite faint and would need binoculars to be seen. The other bright Novae in the 20th century were Nova Perseus 1901, Nova Aquila 1918, and Nova Hercules 1934. Nova Cygni 1975 lies at a distance of around 4,000 light years.
Novae are binary systems where a small hot star and a larger cooler star orbiting each other. The smaller hotter star pulls gas from the cooler star. This gas then forms a disc around the hot star, this is called a Roche Lobe, when this fills up the gas cascades down onto the surface of the hot star. A tiny percentage of gas is then thrown into space. Here on Earth we see a star appear from where no star was observed before. This is a nova.
In medieval times astronomers called these stars nova which is Latin for new, they are not new stars but we still use the term today. It was thought that stars went novae just once. We now that all novae are recurrent they will all go novae many times during their lifetime.