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January 29: Open cluster M50
The Moon passes 4° north of Jupiter at 9 P.M. EST. The pair shares the central regions of Gemini this evening, with the Moon appearing to the upper left of Jupiter, and framed on the left by the Twins’ bright stars Castor and Pollux.
Despite the bright moonlight, Jupiter should still look excellent through a telescope. Its disk stretches 46” and will show off detail such as alternating light and dark cloud bands. For much of the evening, all four Galilean moons are visible west of the planet. Callisto is farthest west, with Ganymede to its east. Much closer to Jupiter, Io and Europa jockey for position, with Europa passing due north of Io shortly after 8:30 P.M. EST. Prior to this time, Europa is farther west than Io. Afterward, Europa is closer to Jupiter and closing in — the icy moon disappears behind the planet’s northwestern limb in an occultation shortly after 12:30 A.M. EST (now the 31st in the Eastern time zone only, still late on the 30th farther west).
While you’re in this region of the sky, also take the opportunity to split the multiple star Castor with your telescope, revealing two roughly equally bright stars just a few arcseconds apart. Next, look about 1.2’ to this pair’s south — there’s a third star in the system, much fainter than the initial pair (these are 2nd and 3rd magnitude, while the fainter component is 9th magnitude). Each of these three stars is also a double, though none of them can be split with a scope.
Sunrise: 7:10 A.M.
Sunset: 5:17 P.M.
Moonrise: 2:39 P.M.
Moonset: 5:41 A.M.
Moon Phase: Waxing gibbous (96%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
