Mercury is quickly dropping out of sight, so catch this early-morning planet while you still can. Today you’ll find the solar system’s smallest world just 3° high in the east 20 minutes before sunrise. Shining at magnitude –0.6, Mercury is readily visible, though not as eye-catchingly bright as blazing Venus (magnitude –4.6) some 26.5° to its upper right. First-magnitude Saturn, about 9.6° to Venus’ upper right, will likely be invisible in the brightening sky so soon before sunrise.
Through a telescope, Mercury’s disk appears nearly 80 percent lit, but it is also just 6” across. That’s because the tiny planet is approaching superior conjunction, when it sits on the opposite side of the Sun from Earth and our two planets are far apart. Mercury is now nearly 1.2 astronomical units from Earth, or 111.5 million miles (179.4 million km). One astronomical unit, or AU, is the average Earth-Sun distance of 93 million miles (150 million km).
As Mercury’s orbit carries it toward superior conjunction, the planet will appear to drop lower and lower in the sky, rising later and later (i.e., closer and closer to the Sun) each morning. It will soon be unobservable for a time, so get in your last looks now.
By contrast, Earth and Venus are currently quite close to each other in their orbits, so Venus’ disk appears large but less of it is illuminated. Your telescope will show that Venus is only a 38-percent-lit crescent, but its apparent angular size is now 30”.
Make sure to put away your telescope well before sunrise occurs from your observing location, which may differ from the time given below.
Sunrise: 5:47 A.M.
Sunset: 8:07 P.M.
Moonrise: 9:38 P.M.
Moonset: 5:54 A.M.
Moon Phase: Waning gibbous (99%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
For a look ahead at more upcoming sky events, check out our full Sky This Week column.
