Match the word on the left with the definition on the 
                                          right.
____ black dwarf		a. star left at the core of a planetary nebula
____ white dwarf 		b. a red supergiant star explodes
____ nebula 		c. a medium-mass star at the end of life
____ protostar 		d. a large cloud of gas or dust in space
____ supernova		e.such a strong gravitational pull that no light escapes
____ neutron star 		f.  the earliest stage of a star ’s life
____ black hole 		g. the remains of a high mass star