February 23
The Immortal Twin
Sun Position
The Sun is in Pisces near +11° declination. Northern hemisphere days are near 11.5 hours; southern hemisphere days are clearly shortening from late summer.
Sky Highlight
No annual event today. Gemini is well-placed in the evening sky, and both Castor and Pollux are easily found, a chance to compare a white multiple-star system (Castor) against the orange giant next to it (Pollux).
Deep Sky Object
NGC 2392, a planetary nebula (Eskimo Nebula) roughly 2,900 light-years away. A double-shell planetary nebula in Gemini whose innermost filamentary shell is thought to result from a fast stellar wind plowing into slower material ejected earlier in the star's evolution. Visible from both hemispheres; best from northern latitudes in winter.
Featured Star
Pollux (β Gem) is an orange giant just 33.78 light-years away, spectral class K0IIIb, and orbited by at least one confirmed giant planet, Pollux b, discovered in 1993 and among the first planets found around a giant star. Named for the immortal twin in myth, Pollux turns out to have company: a planet no one in antiquity imagined circling a giant star.
Around This Date
- February 23, 1987A neutrino detector in a Japanese zinc mine recorded 12 neutrinos from Supernova 1987A, arriving hours before visible light, the first detection of neutrinos from an extragalactic source. Canadian astronomer Ian Shelton confirmed it photographically from Chile that evening; it was the nearest naked-eye supernova since 1604.
- February 24, 1987Supernova 1987A was observed in the Large Magellanic Cloud, the first naked-eye supernova since 1604, providing a real-time test of stellar evolution models.
The immortal twin has a planet, every star, it turns out, may have company.