How does Nestor react when he realizes who Telemachus' companion is in "The Odyssey"?
When Nestor discovers that Telemachus' companion is the goddess Athene disguised as Odysseus' aged friend Mentor, he responds with reverence and awe. He is thankful that Athene has chosen to bestow her favor on Telemachus just as she did on Telemachus' father Odysseus, and Nestor is overwhelmed at the priviledge of her visit to him as well.
Nestor has invited Telemachus to stay the night at his palace, and Athene requests that Nestor send Telemachus on to Lacedaemon in a chariot in the company of one of his (Nestor's)sons in the morning. She then reveals her divine identity by turning herself into an eagle and flying away, leaving Telemachus in Nestor's care. Nestor is amazed, and asks Athene's blessing on himself and his family in prayer. He promises to offer a ritual sacrifice to the goddess in the form of an unbroken heifer with guilded horns.
Athena declares her intention to "go to Ithaca, to put heart into Odysseus's son Telemachus." Athena and Telemachus decide to go to Pylos to visit Nestor, with Athena disguised as Mentor; Athena bids Nestor not to be "shy or nervous" in his quest to discover what really happened to Odysseus.
After they have spoken with Nestor, Athena "flies away in the form of an eagle," at which Nestor is "astonished." He has already told Telemachus that no god has ever been as fond of a human as Athena once was of Telemachus's father; having discovered Athena's identity, he is "astonished" and tells Telemachus that he will be a great hero one day like his father before him. He then prays to Athena, asking her to bless his family and offering the sacrifice of a gilded-horned heifer in return.