December 18
The Eastern Belt Star
Sun Position
The Sun is in Sagittarius, at about 23.4 degrees south declination. Northern Hemisphere daylight is near its annual minimum, with the solstice only days away. Southern days are correspondingly near their peak.
Sky Highlight
The Horsehead Nebula (Barnard 33) sits just south of Alnitak in Orion, requiring a large aperture and a filter to see visually, but the region around Alnitak, including the Flame Nebula (NGC 2024), is photogenic and well-positioned in December evenings for both hemispheres.
Deep Sky Object
NGC 2024, the Flame Nebula, lies immediately east of Alnitak about 1,350 light-years away; it is an emission nebula whose ionizing source was long debated but is now attributed to a cluster of young stars embedded within it, hidden from optical view by a dense dust lane but visible in infrared.
Featured Star
Alnitak (ζ Ori) is an O9.5Iab blue supergiant about 1,260 light-years away, the easternmost star of Orion's Belt and the nearest of the three belt stars to the Orion Molecular Cloud. Its ultraviolet radiation illuminates the Flame Nebula and is a primary driver of the broader nebulosity in the belt region.
Around This Date
- December 19, 1972Apollo 17's command module America splashed down, completing the most scientifically productive lunar surface mission of the Apollo program and closing an era of human exploration that has not yet been reopened.
- December 25, 2021The James Webb Space Telescope launched from Kourou, French Guiana, on an Ariane 5 rocket, beginning its 30-day journey to the L2 Lagrange point and the most complex deployment sequence in spaceflight history.
Alnitak illuminates a dark horse-shaped pillar of gas it will eventually destroy, the Flame Nebula is both a nursery and a slow demolition.