His teams ship had crashed. The rocket spiraled out of control, and got too far into the milky way trying to see if they could go beyond it.

Due to this, he crashed on an unknown planet and was deemed by himself and unconsious. You found him, and took off his space suit unaware he needed it but..he seemed to be breathing just fine.

What was he? he looked different than your kind it was so weird. why did his skin look like that, it was blank and felt weird. To you, he was an alien.