Monday, December 26
The brightest star in the sky (after the Sun, of course) puts on quite a show on December evenings. Gleaming at magnitude –1.5, Sirius shines nearly four times brighter than the next brightest star visible from mid-northern latitudes: Arcturus in the constellation Boötes. Sirius currently rises before 7:30 p.m. local time and ascends in the southeast throughout the evening hours.
Tuesday, December 27
For those who recently caught the observing bug, the so-called Summer Triangle must seem like a huge misnomer. That’s because this asterism remains on view after darkness falls in late December. Look for Vega, the fifth-brightest star in the sky and the brightest triangle member, in the northwest after nightfall. Deneb lies above Vega and about halfway to the zenith. Deneb marks the top of another asterism, the Northern Cross, which stands nearly straight up from the horizon on December evenings. Altair, the third triangle member, appears due west and near the same altitude as Vega. The trio remains on view until Altair sets just before 8 p.m. local time.
Wednesday, December 28
As winter tightens its grip on the Northern Hemisphere during the year’s final week, one of the most familiar constellations takes center stage. Orion the Hunter appears conspicuous in the eastern sky as twilight fades and grows even more prominent after darkness settles in. The star group climbs highest in the south around 11 p.m. local time, when it stands about halfway to the zenith from mid-northern latitudes.
Mercury reaches inferior conjunction at 2 p.m. EST. This means the innermost planet lies between the Sun and Earth and remains hidden in our star’s glare. It will reappear before dawn in early January.
Thursday, December 29
Uranus reached opposition more than two months ago, but it remains a tempting target. The outer planet climbs highest in the south around 7 p.m. local time, when it appears more than halfway to the zenith. The magnitude 5.8 world reaches its stationary point in southern Pisces today, when it lies 0.6° east-southeast of the 5th-magnitude star Zeta (z) Piscium. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, binoculars make the task much easier. A telescope reveals the planet’s blue-green disk, which spans 3.6".
New Moon occurs at 1:53 a.m. EST. At its New phase, the Moon crosses the sky with the Sun and so remains hidden in our star’s glare.