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Matters of Darkness and Light

Look for the moon’s shadowy face on these shortest nights

The waning crescent moon heralds the coming sun in pre-dawn eastern skies through week’s end. So close to the sun’s glow, there’s more to this moon than meets the eye. While the crescent appears clearly aglow, the supposedly missing face appears as a dark notch. This is a result of earthshine, sunlight reflected off our planet that casts a shadowy glow over the rest of the moon’s visible face. This is not to be confused with seeing the dark side of the moon, which is always turned away from earth and thus never visible.
    If you’re up before the sun Saturday, look for the moon in the northeast with Jupiter a half-dozen degrees below. Lower still, Venus is back, slowly rising from the glare of morning twilight. Sunday a wisp of a crescent moon rises barely 90 minutes before dawn, with Jupiter now a few degrees above and Venus six degrees below.
    As the evening sky darkens, Mercury pops into view low in the west-northwest. Visible for less than 45 minutes after sunset, Mercury is tough to spot so close to the horizon and is another target better viewed with binoculars. Easier to spot but distinctly less bright are the twin stars of Gemini Castor and Pollux 10 degrees to its upper right.
    Orange Mars shines high in the southwest at sunset, midway between the equally bright lights of Regulus to the west and Saturn to the east.
    These are the shortest nights of the year, with solstice and the official start of summer less than a week away on June 20. Already we have passed the year’s earliest sunrise, on June 13, and each week now the sun will rise a full minute later. Yet the latest sunset isn’t until the 27th, a span created by Earth’s elliptical, egg-shaped orbit and its changing speed around the sun.