Hakucho (Japanese for “swan”) was Japan’s first x-ray telescope, launched on February 21st 1979, despite having the pre-launch name “CORSA-B”, which suggests it might, at best, be the second. The original CORSA telescope had failed to launch in February 1976, and Hakucho was a replacement.
Hakucho carried eleven x-ray counters, providing readings for the three onboard experiments. Its main work was the study of transient phenomena, especially x-ray bursts, and high on the list of its successes was the discovery of the transient x-ray binary neutron star, Cen X-4.
1906 ⇒ Discovery of main belt asteroid 586 Thekla by Max Wolf. Thekla is a T-type asteroid of approximately 82 km in diameter. It is named after an early Christian saint who was saved (by a storm) from being burned at the stake.
1938 ⇒ Death of George Ellery Hale.