When and how does Vader learn that Luke is his son?
During the Battle of Yavin, it's fairly clear that Vader does not know that Luke is his son. Or at least, he doesn't sense a familial connection (and he doesn't sense one with Leia either, despite being in the same room with her at least three times). The closest he gets with Luke is sensing his Force abilities during the Battle:
VADER: The Force is strong with this one!
But by the beginning of The Empire Strikes Back, he is aware of Luke Skywalker and knows that he's a member of the Rebellion. When his probe discovers the Rebels on Hoth:
OZZEL: My Lord, there are so many uncharted settlements. It could be smugglers, it could be—
VADER: That is the system. And I'm sure Skywalker is with them. Set your course for the Hoth System. General Veers, prepare your men.
And he isn't surprised when the Emperor later indicates that Luke is the son of Anakin:
PALPATINE: The Force is strong with him. The son of Skywalker must not become a Jedi.
(This is the line from the original 1980 version of this scene.)
So when did Vader learn about Luke? Did the Emperor know that he had lived the entire time and kept it from Vader? Or did both Vader and Palpatine they both learn the truth sometime after the Battle of Yavin?
This thread explains it pretty well. Looks like it happened in a novel between some of the movies.
@Daft - Note that the books quoted (including rise and fall of Darth Vader) are no longer considered canon. They're now "legends".
@Richard I didn't know things could become _non-canon_. Haha... I've been living a lie!
Mysterious the force is, yes
@Daft - This might help you out; http://scifi.blogoverflow.com/2015/01/the-new-star-wars-canon-guide/?cb=1
What's the Canonicity of the theatrical versions vs. the updates? Because the phone call with the Emperor changed pretty drastically between the two.
@Plutor - The more recent version is the canon version. The older version is treated as a deleted scene.
@Richard Which means that, in canon, Han Solo can dodge blaster shots fired from a few feet away.
@KSmarts - Don't shoot the messenger. Admittedly in Greedo's case that's not even an option...
@Richard - Don't worry, in the next release they will replace blasters with walkie talkies
@Richard: If you can find Disney/Lucas support for that statement, "he learned it from the Emperor in the new version of that scene" would be a valid answer.
@Daft It was a real thing. Spielberg replaced the guns in ET with walkie talkies in the 20th anniversary re-release.
Obi-Wan was a friggin' moron for not making his uncle give Luke a different last name. A least Leia had a different last name.
@MarkAdler, or maybe he did, but his uncle didn't like it, 'cause he though Obi-Wan was a fool.
@Plutor - Now that we have a canon confirmation, I thought you might like to reconsider your acceptance. Omegacron's answer is excellent, but is only based on non-canon sources :-)
For anyone who wants the "canon" to be only the original theatrical releases of episodes IV, V, and VI, Imperial spies could certainly have gathered information about the Rebels, and Vader may have learned that those responsible for the destruction of the Death Star include someone named "Luke Skywalker". Going back to his feelings during the Battle of Yavin and the events of the fight with Obi-Wan, he could have easily put two and two together. With Obi-Wan gone, none of the Rebels would have known to think to keep Luke's name a secret.
In the new Disney/Marvel canon, in which all new comics, books, and games are considered to have the same level of canon as the movies, Vader has his first direct confrontation with Luke between Episodes IV and V, but doesn't know who he is. This is shown in Marvel's monthly comic series Star Wars. In Issue #2, after taking Luke's lightsaber, Vader takes a closer look at it and realizes it used to be his own.
Vader is suspicious that Obi-Wan was hiding something, but he doesn't yet realize that Luke is his son (he doesn't learn his name in this scene). It doesn't rule out the possibility that Obi-Wan gave his old apprentice's lightsaber to some random guy he found and trained.
But in Issue 6, Boba Fett learns the name of the young wannabe-Jedi that blew up the Death Star. He relays this information to Vader.
Suffice to say, he's not pleased.
Later, in Issue 6 of Marvel's Darth Vader comic series, this scene is shown again and expanded upon. Vader makes the immediate connection to Padme and having been lied to by the Emperor about the exact circumstances of her death. He makes a hologram call to the Emperor similar to the one in TESB:
The Emperor: Yes, Vader? Ah... I sense your anger. Great anger. Have you something to say? Some proud, defiant words? Or are you wise enough to know your place?
Darth Vader: I am angry. You would not have me otherwise. My anger brought me to you. I want you to know--I will not fail. And I understand us precisely.
It's worth noting that in the 2004 DVD and 2011 Blu-ray edits, considered to be the current state of canon, the conversation with the Emperor mentioned in the original question is altered:
The Emperor: We have a new enemy. The young rebel who destroyed the Death Star. I have no doubt this boy is the offspring of Anakin Skywalker.
Darth Vader: How is that possible?
The Emperor: Search your feelings, Lord Vader. You will know it to be true. He could destroy us.
Darth Vader: He's just a boy. Obi-Wan can no longer help him.
The Emperor: The Force is strong with him. The son of Skywalker must not become a Jedi.
It's strongly implied here that Vader and the Emperor had never discussed Luke up until this point. Vader's line "How is that possible?" could originally have meant anything from that he didn't know previously, to that he had guessed but didn't understand the particulars given that he'd thought he'd killed Padmé on the landing platform, to that he wanted to pretend that he hadn't known and was "playing along" the same way that the Emperor was referring to Anakin Skywalker as a third party, to that he knew the Emperor hadn't known and wanted to hide the fact that he, Vader, had known. This new information eliminates the first interpretation, but the exact meaning of Vader's "how is that possible" is still up to speculation as of issue 6 of the comic series.
Hmm. Although he does clearly recognises the saber as his own, there's no indication in the issue that he worked out that Luke is his son or even that he was the pilot in question, merely that he had "underestimated him".
@Richard The pilot part isn't necessarily a component of him figuring it out outside of Legends, but yeah, I edited to clarify a bit more that this is just all we have so far.
@Richard That's fair, although that means the most technically accurate answer would be "it is unknown how he figured it out apart from what's in the 2004 edition of TESB".
Just read the issue. Vader doesn't make the full connection just yet, but is suspicious of Obi-Wan hiding something. Upvoted for being helpful even if it's not a perfect answer just yet.
I thought in the new canon, only comics/shows/etc published after the reboot (~April 2014) were considered canon. Previous non-film material was downgraded to "Legends".
I haven't read the new series yet so I don't know the full story context, but I'm pretty sure that so far they haven't given exact dates to any of the new comics, other than that the series takes place after *Heir to the Jedi*, which itself takes place "shortly after" ANH. I got the images from this free preview of the issue: http://www.starwars.com/news/star-wars-2-first-look
Concerning the meaning of "how is that possible" in light of #6, I see two possibilities: Either Vader managed to keep _his_ knowledge of Luke's identity a secret from Sidious and thus feigned ignorance (or managed to stop his "how did _you_ figure that out?" from admitting to it); or it's what he clarifies in his next sentence "he's just a boy" - how could "just a boy"-Luke manage to blow up an entire Death Star? Ok, or third, after the new trilogy we'll see yet another re-canonization of the original trilogy...
The new canon actually cleans this plot up nicely. Vader is lied to about Padme, serves the Emperor as a broken man. Then, he learns the Emperor lied, and he has a son. So, he is angry about it, and begins to plot to overthrow the Emperor, by converting his son to his side (which we see in ESB). So he doesn't tell the Emperor yet because he's trying to play it cool, until the Emperor calls him on it ("hey look it's a Skywalker") and even then tries to play it off ("he's just a boy, no big deal") but to keep his plan he has to spin it ("hey better yet, let's turn him to the dark side!").