A distant star can be distinguished as a small moon or planet.
LUKE: Look at him. He's headed for that small moon.
HAN: I think I can get him before he gets there...he's almost in range.
The small moon begins to take on the appearance of a monstrous spherical battle station.
BEN: That's no moon! It's a space station.
HAN: It's too big to be a space station.
LUKE: I have a very bad feeling about this.
HAN: No, really, if there were a space station that big, don’t you think we all would have heard about it? Luke, you hear about any job openings for giant space station construction workers in, I don’t know, the last two decades?
LUKE: No, not one.
BEN: It may be possible that the Empire built it using the labor of enslaved worlds.
HAN: If the Empire were imprisoning entire worlds to get slave labor for building a massive space station, surely the Rebel Alliance would have heard about this and gotten the word out. It would generate tremendous sympathy for the rebellion. The rebels have tons of spies, we definitely would have heard about this.
BEN: Perhaps the Emperor is taking special pains to keep this space station a secret.
HAN: But it’s at Alderaan! It has what, a billion people?
BEN: Two billion.
HAN: You can’t hide a giant secret space station if you park it outside a planet with two billion people!
LUKE: But look at the sensors, there is no Alderaan, it’s gone. No witnesses to tell about it.
HAN: Bullshit! Two billion people means what? There would probably be five or ten thousand ships coming and going. Cargo ships, passenger liners, private space craft…
BEN: The machinations of the Emperor’s plans are not always easily understood.
HAN: Okay, so look, I think we can assume if there is a giant space station here, it’s the reason why Alderaan is now an asteroid field, right?
HAN: So, if you had a space station capable of destroying a planet, and you decide to make your first target an unarmed world like Alderaan, the only logical reason would be to intimidate star systems into submission.
Luke heads out of the cockpit and to the central hold.
BEN: That would appear to be the Emperor’s goal. Fear and intimidation are the chief weapons of the Galactic Empire.
HAN: So why not publicize the hell out of such a thing? You can’t scare anyone with a secret space station. You have to scare people with a space station that’s splashed on the front page of every magazine and newspaper in the galaxy.
Luke returns, carrying a thick, paperback book with pages worn from age and frequent use.
LUKE: Hey, so I took a look in this galactic almanac, and Alderaan doesn’t have any moons.
HAN: Oh. That’s a space station.
via College Humor