December 10
The Glittering Head
Sun Position
The Sun is in Sagittarius, about 23.3 degrees south declination. Days are near their shortest in the Northern Hemisphere and their longest in the Southern; the asymmetry between hemispheres is at its December peak.
Sky Highlight
The Orion Molecular Cloud complex sprawls across the region around Orion this week, and while most of it is invisible without specialized equipment, the Orion Nebula and M78 represent the visible tips of an enormous star-forming structure roughly 1,300 to 1,500 light-years away.
Deep Sky Object
NGC 1977, the Running Man Nebula, is a reflection nebula about 1,500 light-years away immediately north of M42 in Orion, an often-overlooked companion to the Great Nebula that appears blue rather than red because it reflects rather than emits light.
Featured Star
Meissa (λ Ori) is an O8III blue giant about 1,100 light-years away that marks the head of Orion, embedded in a faint circular ring nebula (a wind-blown shell roughly 150 light-years across) formed by the star's intense radiation and stellar wind sweeping the surrounding interstellar medium. It burns hot enough to ionize gas across parsecs.
Around This Date
- December 12, 1970Uhuru, launched from Kenya on Kenya's independence day, became the first satellite dedicated to X-ray astronomy and went on to discover X-ray binary stars, confirming that collapsed objects were accreting matter from companions.
- December 7, 1995Galileo entered Jupiter orbit after a six-year journey, making it the first dedicated orbiter of an outer planet and enabling detailed study of the Galilean moons, including early evidence for a subsurface ocean on Europa.
Meissa is a star that has carved its own cavity in the galaxy. It has been remaking its neighborhood since before humans had names for anything.