October 10
The Faintest Tip
Sun Position
The Sun is in Libra near -8° declination. For observers at 50°N, the Sun is setting before 6:30 PM local time; for observers at 35°S, sunset is pushing past 7 PM toward the long evenings of southern summer.
Sky Highlight
Cassiopeia is nearly overhead for observers at mid-northern latitudes on October evenings, and the entire W asterism transits close to the zenith, making tonight a good opportunity to trace the Milky Way running directly through it. The richest star fields of Perseus lie immediately south.
Deep Sky Object
NGC 663, an open cluster about 6,850 light-years away. NGC 663 in Cassiopeia is a rich, compact open cluster containing roughly 400 stars, bright enough to spot in binoculars and rewarding in a small telescope. It sits embedded in one of the denser patches of the Milky Way visible from northern skies. Best for Northern Hemisphere observers; from far southern latitudes it remains below the horizon.
Featured Star
Segin (ε Cas) is a blue-white giant (B3III) about 442 light-years away, the faintest of the five stars that make up Cassiopeia's W, and at that distance the least obviously powerful. Were it as close as Ruchbah, it would outshine every star in the W by a wide margin. Segin, the faintest tip of Cassiopeia's W, a giant hiding behind its distance.
Around This Date
- October 10, 1846William Lassell discovered Triton, Neptune's largest moon, just 17 days after Neptune itself was confirmed, making it one of the fastest satellite discoveries in history.
- October 11, 1968Apollo 7 launched, the first crewed Apollo mission, successfully testing the command module after the Apollo 1 fire that had grounded the program for twenty months.
Distance is the great equalizer in astronomy: a dim point and a blazing furnace can look identical from far enough away.