question: After a supernova, what part of a star remains?
distractor3: superficial
distractor1: large
distractor2: outer
correct_answer: core
support: After a supernova explosion, the star's core is left over. This material is extremely dense. What happens next depends on the core's mass. The core might be less than about four times the mass of the sun. In this case, the star will become a neutron star. A neutron star ( Figure below ) is made almost entirely of neutrons. A neutron star has more mass than the sun; yet, it is only a few kilometers in diameter.