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Where’s the moon? Waxing crescent

The moon reaches first quarter on August 10. That means there will be some moon-free hours before dawn for the Perseid meteor peak, morning of August 12.

August 7, 2016 waxing crescent moon via EarthSky Facebook friend Marcia White Bower in Syracuse, New York.  Thanks, Marcia!

August 7, 2016 waxing crescent moon via EarthSky Facebook friend Marcia White Bower in Syracuse, New York. Thanks, Marcia!

A waxing crescent moon – sometimes called a young moon – is always seen in the west after sunset.

At this moon phase, the Earth, moon and sun are located nearly on a line in space. If they were more precisely on a line, as they are at new moon, we wouldn’t see the moon. The moon would travel across the sky during the day, lost in the sun’s glare.

But a waxing crescent moon is far enough away from that Earth-sun line to be visible near the sun’s glare – that is, in the west after sunset. This moon phase is seen one day to several days after new moon. On these days, the moon rises one hour to several hours behind the sun and follows the sun across the sky during the day. When the sun sets, and the sky darkens, the moon pops into view in the western sky.

The moon is now waxing toward first quarter. Next first quarter moon will be August 10, 2016 at 1821 UTC. Translate to your time zone. That means that there will be a relatively bright moon in the evening sky on the peak night of the Perseid meteor shower – evening of August 11, morning of August 12 – but that the morning sky, when the most meteors are typically flying, will be moon-free in the predawn hours.

Perseid outburst expected in 2016

This month's waxing crescent moon near Jupiter on August 5, 2016. Photo by John Entwistle in Corolla, Outer Banks, North Carolina.

This month’s waxing crescent moon near Jupiter on August 5, 2016. Photo by John Entwistle Photography in Corolla, Outer Banks, North Carolina. See more photos of this month’s moon near planets.

Note that a crescent moon has nothing to do with Earth’s shadow on the moon. The only time Earth’s shadow can fall on the moon is at full moon, during a lunar eclipse. There is a shadow on a crescent moon, but it’s the moon’s own shadow. Night on the moon happens on the part of the moon submerged in the moon’s own shadow. Likewise, night on Earth happens on the part of Earth submerged in Earth’s own shadow.

Because the waxing crescent moon is nearly on a line with the Earth and sun, its illuminated hemisphere – or day side – is facing mostly away from us. We see only a slender fraction of the day side: a crescent moon. Each evening, because the moon is moving eastward in orbit around Earth, the moon appears farther from the sunset glare. It is moving farther from the Earth-sun line in space. Each evening, as the moon’s orbital motion carries it away from the Earth-sun line, we see more of the moon’s day side. Thus the crescent in the west after sunset appears to wax, or grow fatter each evening.

Here’s more to look for in tonight’s sky

Jupiter, Mercury, moon and Venus after sunset at Jerudong beach, Brunei, on the island of Borneo. Photo by Zefri Besar.

This month’s waxing moon ascended in the west after sunset, over the course of several evenings, near bright planets. Here’s Jupiter, Mercury, moon and Venus after sunset on August 4, 2016 at Jerudong Beach, Brunei, on the island of Borneo. Photo by Zefri Besar. See more photos of this month’s moon near planets.

The pale glow on the darkened portion (night side) of a crescent moon is called earthshine. Is caused by light reflected from Earth’s day side onto the moon. After all, when you see a crescent moon in Earth’s sky, any moon people looking back at our world would see a nearly full Earth. Read more: What is earthshine?

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

Moon in 2016: Phases, cycles, eclipses, supermoons and more

Check out EarthSky’s guide to the bright planets.

Deborah Byrd

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