Neil Degrasse Tyson is an American astrophysicist, have you heard of him? 
I have never heard of him
Oh he is really cool, Since 1996, he has been the Frederick P. Rose Director of the Hayden Planetarium. He also hosted Cosmos.
what exactly is an astrophysicist
They are those that have a degree in astronomy. For example,Neil Degrasse Tyson received a master's degree in astronomy
Oh, ok, what is the Hayden Planetarium?
A planetarium is a theatre built for presenting shows about astronomy. The hayden planetarium is in Los Angeles.