The competition is getting fierce as Rush's deep-space magnum opus "Cygnus X-1" goes head-to-head against Styx's "Come Sail Away" in this round of our Rock Star Wars tournament.

To try and fill our days between now and the Dec. 18 arrival of Star Wars: The Force Awakens, we’ve tracked down 32 space-themed classic rock songs and paired them off against each other in a series of intergalactic battles. We’re down to four now. The field will be halved every week based on your votes, until only the spaciest song in rock history is left.

Both of our contestants in this round have enjoyed stratospheric success in recent rounds. Rush soared past Creedence Clearwater Revival's "It Came Out of the Sky" with more than 72 percent of the vote before moving on to face the David Bowie classic "Space Oddity" — and they really turned on the jets in that match, racking up more than 74 percent at the polls.

Styx, meanwhile, earned the voters' seal of approval against Deep Purple's "Space Truckin'," taking away a little more than 63 percent of the vote, then bested Elton John's "Rocket Man," cruising to victory with over 58 percent of the final tally.

So which of these deep space classic rock masterpieces will win the right to move on to the finals? You can listen to both tracks below, and vote once per hour in each of the this round’s Rock Star Wars battles until polls close on Dec. 14 at 11:59PM ET. Your choice for our Rock Star Wars champion will be revealed on Dec. 22, 2015.

Listen to Rush's 'Cygnus X-1'

Listen to Styx's 'Come Sail Away'