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Where’s the moon? Waxing gibbous

Full moon is coming up on the night of May 10.

Waxing gibbous moon by Patrick Casaert. He posted it at EarthSky Facebook and also on his page Les Avions et la Lune (The Planes and the Moon) on Facebook.

A waxing gibbous moon appears high in the east at sunset. It’s more than half-lighted, but less than full.

That’s another way of saying that a waxing gibbous moon phase falls between a first quarter moon and a full moon. Next full moon comes on May 10, 2017 at 21:42UTC; translate to your timezone).

Relative to a new moon – which is more or less between the Earth and sun, located near the sun along our line of sight – a waxing gibbous moon has moved in its orbit so that it’s now relatively far from the sun in our sky.

A waxing gibbous moon rises during the hours between noon and sunset. It sets in the wee hours after midnight.

Point of interest on a waxing gibbous moon: Sinus Iridum (Bay of Rainbows) surrounded by the Jura Mountains. Photo by Lunar 101-Moon Book in Toronto, Canada.

Another shot of the waxing gibbous moon, with Sinus Iridum (Bay of Rainbows) clearly visible, from P. Weeks in Greenville, North Carolina. Watch for it!

People often see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a large fraction of the moon’s day side is facing our way.

Thus a waxing gibbous moon is more noticeable in the sky than a crescent moon, with only a slim fraction of the lunar day side visible. Also, a waxing gibbous moon is far from the sun on the sky’s dome, so the sun’s glare isn’t hiding it from view.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed. A gibbous moon can also be a waning gibbous, in the week between full moon and last quarter moon.

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

Deborah Byrd