The title of this episode, Black Sun, refers to a black hole in space, which has a very strong gravitational pull.
Mike Ryan: I'm in position. What a sight! It's round, it's huge, it's black. Boy, is it black!
Kano: But Computer will have to be deactivated for the force field.
Bergman: Yes, well, it can do with a rest.
Bergman: It's an extraordinary thing, how we've survived. I put the probability through the computer. I thought the computer was going to blow up figuring the odds. They're just about infinite.
Koenig: Victor, if you're trying to cheer me up, you're not succeeding.
Sandra: I will be all right.
Helena: Sure you will. I remember when I was a little girl, I was afraid of the dark. Isn't that funny?
Sandra: And I was afraid of doctors.
Koenig: Do you have any idea what'll happen to us inside the black sun?
Bergman: Whatever it is, I just hope it's interesting.
Alan asks the Eagle pilot for sonar readings off the Black Hole, but sonar does not function in the vacuum of space!