October 16
The Distant Giant
Sun Position
The Sun is in Libra near -11° declination. The Northern Hemisphere's solar angle is now noticeably oblique, reducing daylight heating even on clear days; the Southern Hemisphere is receiving more direct sunlight than at any point since March.
Sky Highlight
Mid-October brings Perseus to good evening altitude in the Northern Hemisphere, and the Perseus Moving Group (a loose stellar association containing many of Perseus's bright stars) can be appreciated as a genuine physical structure, not just a line-of-sight alignment. For Southern Hemisphere observers, Perseus rides low in the north.
Deep Sky Object
NGC 869 / NGC 884 (Double Cluster), an open cluster pair about 7,500 light-years away. The Double Cluster in Perseus is a naked-eye object under dark skies and one of the most rewarding targets in a modest telescope, two dense, glittering clusters separated by a small gap, each containing thousands of young stars and a scattering of luminous red supergiants. Best for Northern Hemisphere observers in autumn; from far southern latitudes it is below the horizon.
Featured Star
Segin (ε Cas) is a blue-white giant (B3III) about 442 light-years away, more than four times the distance of its W-mates Ruchbah and Caph. At that distance it still appears as a solid naked-eye star, which is a hint at how intrinsically powerful it is. It anchors the trailing end of Cassiopeia's W. Segin, the faintest tip of Cassiopeia's W, a giant hiding behind its distance.
Around This Date
- October 16, 1962President Kennedy was briefed on reconnaissance photographs confirming Soviet ballistic missile installations in Cuba, triggering the Cuban Missile Crisis, a standoff with direct consequences for the development of military satellite reconnaissance programs.
- October 18, 1963France launched the first cat in space, Félicette, on a suborbital trajectory from Algeria; she survived and was recovered after a successful parachute descent.
Segin is the kind of star you stop noticing once you know the W, which is a good argument for occasionally asking what the faint ones really are.