A nuclear reaction in which the nuclei of two atoms combine to form a larger nucleus.
A nuclear reaction in which an atomic nucleus is split into two smaller parts.
An expanded star, with cooling outer layers.
The dense core left after a high-mass star has exploded as a supernova.
A spinning neutron star that appears to give off strong pulses of radio waves.
An object whose surface gravity is so great that not even electromagnetic waves can escape from it.
The small, dense, but dim remains of a low- or medium-mass star.
A very large, massive, bright star ranging in size from 100 to 1000 times the diameter of the sun.
An enormous explosion in which the byproducts of a supergiants star's lifetime of fusion are flung into space.
A glowing cloud of gas surrounding a dying low-mass star.
An apparent change in position of an object with respect to a distant background when viewed from different locations.
A diagonal band of the H-R diagram, which represents about 90% of all stars.
A large, massive, bright star that is somewhat smaller and fainter than a supergiant.
A contracting nebula with enough mass to form a star.
A large cloud of gas and dust spread out over a large volume of space.