December 4
The Middle Pearl
Sun Position
The Sun is in Sagittarius, at about 22.6 degrees south declination. Northern Hemisphere nights stretch past 15 hours at high latitudes; southern latitudes are near their longest days.
Sky Highlight
The Orion Nebula (M42) transits the meridian around 1 AM local time for mid-northern observers and is visible all evening in the southeast. Its faint glow is detectable with the naked eye from a dark site; binoculars reveal the nebula's extent, and any small telescope shows the Trapezium cluster within.
Deep Sky Object
M42, the Great Orion Nebula (emission nebula, about 1,344 light-years away) is an active stellar nursery and one of the nearest regions of ongoing star formation; the newborn Trapezium stars are illuminating gas their own formation disrupted, making it one of the most photographed objects in the night sky.
Featured Star
Alnilam (ε Ori) is a B0Ia blue supergiant roughly 1,340 light-years away, the middle star of Orion's Belt, and one of the most intrinsically luminous stars visible to the naked eye. It burns with a power roughly 275,000 times the Sun's, but distance keeps it looking merely bright rather than overwhelming.
Around This Date
- December 7, 1972On the way to the Moon, the Apollo 17 crew photographed Earth as a fully illuminated disk against the black of space, an image that became one of the most reproduced photographs in history.
- December 8, 2010SpaceX's Dragon capsule became the first commercially built spacecraft to successfully orbit Earth and be recovered, completing two orbits before splashing down in the Pacific Ocean.
A supergiant threading the Belt. Alnilam is the quiet anchor of one of the most recognized patterns in human sky-watching.