December 28
The Heavy One
Sun Position
The Sun is in Capricorn, at about 23.1 degrees south declination. Northern Hemisphere days are adding a few seconds each day, a gain invisible without measurement but real. Southern days continue their modest post-solstice decline.
Sky Highlight
Canis Major's prominent stars are well-placed in the southeastern sky this evening for northern observers, and Wezen is part of the easily-traced figure of the large dog below and left of Sirius. From southern latitudes, the whole figure is high in the northern sky.
Deep Sky Object
NGC 2354 in Canis Major, an open cluster about 13,500 light-years away, is an older, sparse cluster visible in small telescopes, a contrast to the young nearby clusters that dominate the Canis Major-Puppis region, and a reminder that the disk of the Milky Way holds stellar populations of all ages.
Featured Star
Wezen (δ CMa) is an F8Ia yellow-white supergiant about 1,600 light-years away, blazing with roughly 50,000 times the Sun's luminosity, a figure that earns the 'heavy one' name given it in medieval Arabic astronomy. It appears as a modest second-magnitude star only because of its distance; at 50 light-years it would be as bright as a crescent Moon.
Around This Date
- December 28, 1882Arthur Eddington was born; he became one of the first to fully understand the physics of stellar interiors, and his work on stellar structure in the 1920s established the mass-luminosity relationship that governs how stars across the universe age and die.
- December 28, 1612Galileo Galilei sketched and recorded a star-like object near Jupiter that was in fact Neptune; he observed it again on January 27, 1613, noting it had moved relative to nearby stars, but did not identify it as a planet. Neptune's discovery would wait another 234 years.
Wezen carries 50,000 suns of power across 1,600 light-years to reach your eye as a second-magnitude star, the distance swallows the fire.