Most people never get to experience a total solar eclipse, when the moon blots out the disk of the sun and reveals its fiery outermost atmospheric layer, or corona.

After nearly seven hours, the astronauts' lunar observation period is wrapping up.

At 6:44 p.m. Eastern time, the crew of NASA’s moon mission Artemis II — three Americans and one Canadian — became the first astronauts in more than half a century to be cut off from the rest of humani...