The Sky This Week for January 19 to 22

Thursday, January 19

•  Last Quarter Moon occurs at 5:13 p.m. EST. The Moon doesn’t rise until nearly 1 a.m. local time tomorrow morning, however, by which time it will appear slightly less than half-lit. The Moon spends the morning hours on the border between Virgo and Libra.

•  Mercury reaches the peak of its current apparition this morning. The innermost planet lies 24° west of the Sun at 5 a.m. EST and appears 10° above the southeastern horizon 30 minutes before sunrise. Shining at magnitude –0.2, it shows up nicely through the twilight glow. (If you don’t spot it right away, binoculars will bring it into view.) A telescope reveals Mercury’s 7″-diameter disk, which appears slightly more than half-lit.

Friday, January 20

•  One of the sky’s most familiar constellations rules January’s sky from dusk until the early morning hours. Orion the Hunter appears conspicuous in the southeast after darkness falls and climbs highest in the south around 9 p.m. local time. It then stands about halfway to the zenith from mid-northern latitudes. The night sky’s brightest star, Sirius, trails about an hour behind Orion.

•  Jupiter passes 4° due north of 1st-magnitude Spica, the brightest star in Virgo the Maiden. The brilliant planet shines nearly 20 times brighter than the star.

Saturday, January 21

•  Although Saturn passed on the opposite side of the Sun from Earth in December, it already appears low in the southeast before morning twilight commences. From mid-northern latitudes, the ringed planet lies about 10° above the horizon at the start of twilight. It shines at magnitude 0.5, which makes it the brightest point of light in its host constellation, Ophiuchus the Serpent-bearer.

•  The Moon reaches apogee, the farthest point in its orbit around Earth, at 7:14 p.m. EST. It then lies 251,602 miles (404,914 kilometers) from Earth’s center.

Sunday, January 22

•  Two of the finest deep-sky objects shine prominently on evenings during January. The Pleiades and Hyades star clusters appear highest in the south in early evening but remain conspicuous until well past midnight. The Pleiades, also known at the Seven Sisters and M45, looks like a small dipper to naked eyes. The larger Hyades forms the V-shaped head of Taurus the Bull. Although both look nice with naked eyes, binoculars show them best.