Ok here for the love of god. DO NOT ASK HIM OUT. THIS IS THE DUMBEST THING TO DO. I don't care who you are but you are seriously taking away his manliness. Give him a lot of IOI (indicators of interests)
Here's a list of IOI you can do with him
http://www.pick-up-artist-forum.com/list-of-iois-vt36387.html
If he still isn't biting, give up because a real man would see these IOI and ask you out already unless he's just generally not interested in you.
ASK HIM OUT TO GO CLUBBING WITH YOU AND YOUR FRIENDS. Then atleast become intimate there. Get drinks
Honestly if you really have fallen in love with this astrophysicist, have sex with 12 guys and if you still want the astrophysicist, then proceed and get him.