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 January. Look for Vega, the fifth-brightest star in the sky and the brightest triangle member, low in the northwest. Deneb lies above Vega and about one-third of the way to the zenith. Deneb marks the top of another asterism, the Northern Cross, which stands nearly straight up from the horizon on January evenings. Altair, the third triangle member, scrapes the western horizon and sets around 6:30 p.m. local time.
Saturday, January 19
Although Uranus reached opposition and peak visibility nearly three months ago, it remains a tempting target. The outer planet appears nearly 60° high in the southwest after darkness falls and doesn’t set until after midnight local time. The magnitude 5.8 world lies in southeastern Pisces, some 1.2° north of the 4th-magnitude star Omicron () Piscium. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. A telescope reveals Uranus’ disk, which spans 3.6″ and shows a distinct blue-green hue.
Sunday, January 20
Anyone with clear skies across the Americas can witness this week’s biggest event: a total eclipse of the Moon. The Full Moon, which arrives officially at 12:16 a.m. EST tomorrow morning (9:16 p.m. PST this evening), then lies deep in Earth’s shadow. The eclipse’s partial phases start at 10:34 p.m. EST. The shadow appears dusky gray at first, but as more of the Moon sinks into the shadow, it should take on a distinctly orange color. The color comes from sunlight refracted and scattered through Earth’s atmosphere, and appears most prominent during totality, which lasts from 11:41 p.m. to 12: 43 a.m. EST.
Monday, January 21
Near-Earth asteroid 433 Eros continues its close encounter with Earth this week. It glows at 9th magnitude, bright enough to see through small telescopes. The asteroid resides in southwestern Auriga, and tonight it passes 2° west of 3rd-magnitude Iota () Aurigae. This region lies high in the east after darkness falls and passes nearly overhead around 9 p.m. local time. Be sure to catch Eros this month — it won’t be as close or as bright again until 2056.
The Moon reaches perigee, the closest point in its orbit around Earth, at 3:00 p.m. EST. It then lies 222,042 miles (357,342 kilometers) away from us.