R2

Luke's temple wasn't necessarily on Ach-to, though. He could've sent Artoo in a different X-Wing, or left him at the ruined temple.

Heck, Artoo could've come to Ach-to with Luke in his own X-wing and left for the Resistance once Luke knew he was safe- or maybe Luke didn't even immediately leave for exile on Ach-to, but took care of some housekeeping first.

It's vague enough to be answered by a lot of things, actually.

 

Prolly just flew away with his rocket feet #PrequelsLogic

 

Well we know droids can fly ships without a pilot so that's probably what happened. Obi-Wan: "Take the fighter back to the ship. Tell Cody I made contact."

 

This has been bugging me recently and glad to see someone else ask the question as well.

It seems odd Luke didn’t take R2 with him to search for the temple (and therefore Ach-to) especially if he had had R2 with him while training the new Jedi.

But to me it’s even more strange that it then appears there was no droid with him at all when he was flying his X-wing (that ends up in the ocean) around?

The absence of R2 in TFA would seem to be so much more plausible if he had been with Luke the whole time rather than “asleep.” Just kind of an odd story choice IMO.

 

After Luke decided to go into exile alone AFTER his new Jedi Academy was burned, R2-D2 was deliberately left with Luke's sister, Leia Organa.

To avoid being tracked, Luke removed a section of R2's highly detailed Imperial galactic map (obtained from ANH's first Death Star main computer) which containing the location of Ahch-To from his memory. Before he left, Luke commanded R2-D2 to defrag his memory, knowing that would keep him busy and quiet. Luke then flew off alone in an X-Wing to Ahch-To, where he concealed his X-Wing offshore underwater.

The section of map containing Ahch-To's location was stored for safe-keeping on a memory device that somehow later came into the possession of Lor San Tekka on the planet Jakku. Poe Dameron was sent to Jakku in TFA to retrieve the map fragment.

In Luke's absence, R2-D2 appeared to be in "depression", but wasn't. Awaiting the day that his master returned, R2-D2 usefully spent his time defragging his cluttered and disorganised memory sectors after his many years of afventures and experiences, having never had a memory wipe. While he appeared to be "depressed" and was stored out of the way under a tarp, R2-D2 was fully concious of his surroundings at all times.

 

I don't think Luke would simply leave to find the temple without meeting up with his support group at least once or letting someone know what had happened. I mean, you don't send your kid off to private school and not find out what happened when everyone gets killed or disappears. He told Han and Leia what happened and left R2 with Leia. If he hadn't, I'm not sure how Han, Leia or anyone else would know that Kylo Ren was Ben Solo. Actually, we still don't know that. How did Leia and Han know that Ben had become Kylo Ren? Was there some contact after the incident at Luke's academy? How do they even know who Snoke was if the First Order just showed up as suddenly as it appears onscreen? This is where the lack of backstory bugs me with Snoke and the First Order. What happened with all this stuff between Snoke, Han, Leia, Ben and possibly Luke?

 

Damn, Lore-master alert