Leave it to President Barack Obama to surprise America’s most-admired geek.

Obama delivered a special introduction to astrophysicist Neil deGrasse Tyson’s reboot of “Cosmos: A Spacetime Odyssey,” which premiered Sunday night on 10 channels.

Tyson, delivering a keynote address, told crowds at Austin’s SXSW that he didn’t know the president would be doing the introduction until Saturday.

“With the President of the United States participating in the rollout of a scientific adventure, I think there is no better evidence that we do have a future that we can dream of,” Tyson told the crowd. His chapter comes more than 30 years after Carl Sagan’s “Cosmos: A Personal Voyage.”

A bit of the old “Cosmos” has been embedded in the new: Sagan’s wife, Ann Druyan, who co-wrote the Emmy-winning show with him, is an executive producer on the reboot.

Tyson’s an affable crusader for science; he’s appeared on the “Daily Show,” where he politely told host Jon Stewart the earth in the opening credits was spinning in the wrong direction. And he’s done multiple stints on “Real Time with Bill Maher.”

This isn’t the first time President Obama has endorsed science programming. He also appeared on “Mythbusters,” where he challenged Adam Savage and Jamie Hyneman to re-test the myth of Archimedes’ solar death ray.