The new moon fell on Thursday, September 5. That’s when the moon passed most nearly between the Earth and sun for this monthly orbit. It’s when the moon was traveling across the sky with the sun during the day. After new moon, the moon passes from the morning to the evening sky, so that, a day or two later, a thin waxing crescent moon shows up in the west at dusk. That could happen tonight – September 7, 2013 – in your sky.
Will you see the young crescent moon beneath the dazzling planet Venus at evening dusk tonight? You might, if it’s clear and no obstructions block your view of the southwestern and western sky.
If you miss the moon this evening, try again after sunset tomorrow, when there will be a dramatic pairing of the moon and Jupiter. The waxing crescent will be larger and brighter on September 8, and it’ll couple up more closely with Venus. Read about the September 8 moon-Venus pairing here..
Then on Monday, September 9, the moon will pair with Saturn in the western twilight. Read about September 9′s twilight sky here..
By the way, you may – or may not – need binoculars to see Spica, the brightest star in the constellation Virgo, near Venus.
The moon moves continuously in orbit around Earth. As seen on our sky’s dome, the orbital motion of the moon carries our companion world farther from the sun-Earth line each day. And thus tonight’s moon is farther from the sunset than last night’s moon.
Still, autumn is nearly upon us in the Northern Hemisphere. That means we’ll have a harder time catching the young crescent moon, Venus, Spica and Saturn after sunset than they do in the Southern Hemisphere. Spica, a spring and summer star, fades in the twilight dusk at this time of year. At our northerly latitudes, the ecliptic – the path of the sun, moon and planets – makes a narrow angle with the horizon at sunset in September and October. This fact keeps the waxing crescent moon low in the sky – and tougher than usual to see.
The whereabouts of the ecliptic in our sky is related to Earth’s orbit around the sun. (Are you getting an idea of cycles upon cycles in the celestial sphere? You should, because that’s the reality.) Earth’s tilt on its axis – which carries the sun low in winter and high in summer – also keeps the young crescent moon from being easily visible after sunset in September and October.
But the sky is nothing if not reliable. The moon will keep moving in orbit around the sun, and thus the crescent moon in our evening sky will keep moving farther from the sunset each night. You’ll see it one night soon, if you don’t see the moon beneath Venus tonight.
Bottom line: On Saturday night, September 7, 2013, the moon will just be returning from being most nearly between the Earth and sun for this month. If you see it, it’ll be a thin crescent low in the west after sunset. The brilliant planet Venus and fainter planet Saturn will appear above the moon in the September 7 evening sky. Don’t miss the dramatic pairing of the moon and Venus on September 8!