Oyu is a space whale!
He does not actually look very much like a whale. That is because he lives in space. So instead of normal baleen, he has space-baleen, which filters out delicious baryonic matter from the solar wind! And instead of a water-spout, he has a set of ion-spouts, which fire charged particles in any one of three directions to give him fine control over his direction! And instead of flukes and a tail, he has vast sheets of diaphanous matter spanning dozens of square miles, allowing him to sail by virtue of the propulsion of the solar wind alone!
Humanity met him, sort-of. They found him with their telescopes and their space-rays, and they sent out radio signals: "Hello! Are you there? Can you hear us? What do you think of this sequence of primes, and this list of the digits of pi?" Eventually, they would probably have sent an expedition to meet him face-to-face.
Oyu is a clever creature. He figured it out! But he had no real way to respond. And by the time he managed to redirect his course, putting himself in position for a close fly-by of Earth, humanity was dead!
(It wasn't his fault. They'd just been too friendly - and there are some things in space that are not friendly at all! So they sent self-replicating probes to bombard Earth with asteroids and melt the surface into glass. It was a tragedy! We will avoid speaking of it further.)
Oyu noticed the radio-signals stop. He was sad.
But then, one year, he noticed something odd.
More radio signals - like the ones the Earth sent, before its extinction - but not coming from that?
Had someone survived?
Nope! Humanity was thoroughly dead.
But before their death, they had managed to send out a pair of robot probes. One of them went to Mars. And the other one went to Oyu!
"Hello hello hello," the probe said to Oyu as it cruised steadily closer on its tiny ion drive. "earth is dead asteroids hit us we didn't have time to stop them but i have the complete genome of the human race also history science religion and a hidden copy of pong as an easter-egg would you please let me settle on you and try to begat a new human race"
It talked very quickly, and used many unfamiliar symbols. It took Oyu some time to understand what the little robot was saying. And, of course, even when it did, it couldn't respond! But Oyu knew what it would have said, if it could.
"Little robot," it would have said, "I am too fragile and tiny a creature for you to restart a species on; I am a thing of starstuff, not of terrestrial matter! But here - bury yourself within me, and I will take you to the distant moon of the red-swirling giant, Io/Jupiter. There you may begat to your hearts content."
So it went.
Hurrah for Oyu!