Luke does reach out, mostly just to see what there is and he almost misses her under the rumble and thunder of Vader's presence.

But she's near and she's not a fan of the Empire and there's an off chance he can try and get a message to the Rebellion, let them know he's alive for now. He doesn't know if he'll be allowed to get near her or if he can speak to her if he does, so he takes a little time, just a little, to find a small rock and carve into it with his mind and a couple of stolen tools.

(He is not good with his left hand and writing.)

He pockets the rock and goes looking for her. At worst, he hopes he can drop the stone near her, the message nice and easy.

To Leia. Love Luke. And a few dots that mark out a particular constellation in a particular sky that they shared once.