Thursday January 19, 2017; 10:04 am EST
Sky Watch - Bright Lights, all Tight
Saturn, Mars and Venus vie for position in the west at twilight
The waning moon rises after 10pm at week’s end, then crests the horizon 20-plus minutes later each night, so that by Tuesday, the last-quarter moon rises after midnight. Friday’s gibbous moon rises with glowing Jupiter only six degrees to the south, and the two remain tight through the wee hours before dawn, appearing high in the south with sunrise Saturday at 6:06.
The sun sets this week around 8:15, and each day it leaves us more than a minute earlier. As the sky darkens, a bright light appears in the sun’s wake. Aside from the sun and moon, Venus is the brightest object in the heavens.
While Venus blazes bright enough to shine through twilight’s haze, true darkness reveals Saturn and Mars higher west. All three planets have been pulling together for several weeks, but for Saturn and Mars, Friday marks their point of closest approach, when brighter Saturn appears less than two degrees above ruddy Mars. Two days later, on August 1, they are only a fraction of a degree farther apart, with Saturn hovering due north of Mars. While Mars and Saturn pull away from one another after the first, Venus is fast on their trail, forming a loose triangle.
A fourth planet joins the post-twilight fray, as Mercury strays its farthest east of the setting sun this week. You won’t have long after sunset to spot Mercury, which appears as the brightest light midway between Venus and the horizon.
Given a dark, clear view of the sky, these moonless summer nights reveal the Milky Way flowing overhead. Dark is the key word here, as even modest light will render this river of stars invisible. Practically dividing our sky in half, the Milky Way stretches from the northern constellation Cassiopeia all the way past the southern constellations of Sagittarius and Scorpius.