context: Supernova is a star explosion that can occur in two different ways. After a fusion, a massive star may collapse under its own gravity into a neutron star or black hole, or in a double star a white dwarf may grow its mass beyond the Chandrasekhar border. [1] Supernovs occur every 50 years on average in the Milky Way galaxy. [1] [2] While hundreds of supernovae were previously detected in different galaxies each year, there were 1454 supernovae discovered in 2013, and the number has grown. [3]
question: What is a supernova?
answers.text: star explosion