December 26
The Uncertain Name
Sun Position
The Sun is in Capricorn, at about 23.2 degrees south declination. The Northern Hemisphere's daylight is incrementally and still barely detectably lengthening; southern days continue their slow retreat from their solstice peak.
Sky Highlight
The year's final days bring Canis Major high enough in the southeast for northern observers to see the full figure of the large dog clearly, Sirius at the dog's shoulder, Adhara, Wezen, and Aludra marking the hind end, and Mirzam at the fore. From the southern hemisphere this is a high, prominent constellation well into the evening.
Deep Sky Object
NGC 2360, an open cluster in Canis Major about 3,700 light-years away, is rich and compact with over 80 stars, an intermediate-age cluster visible in binoculars as a fuzzy patch and nicely resolved in a moderate telescope, often overlooked in favor of brighter M41 nearby.
Featured Star
Muliphein (γ CMa) is a B8II blue-white bright giant about 402 light-years away, the third-brightest star in Canis Major after Sirius and Adhara. Its name is of uncertain Arabic origin and was shared confusingly with stars in other constellations in historical star catalogs; it is a luminous giant that holds its own in a bright-star-rich constellation but has no settled lore to speak of.
Around This Date
- December 27, 1571Johannes Kepler was born; his three laws of planetary motion (that orbits are ellipses, that planets sweep equal areas in equal times, and that the square of the orbital period is proportional to the cube of the semi-major axis) remain cornerstones of orbital mechanics today.
- December 25, 2021JWST launched successfully and began the months-long process of cooling its mirrors and instruments to their operational temperatures before first light observations could begin.
Muliphein is content to be a supporting player in a brilliant constellation, not every star needs a founding myth.