What’s a new moon?

Unless they pass directly in front of the sun, causing a solar eclipse, new moons generally can’t be seen. They cross the sky with the sun during the day. The next new moon happens on August 30 at 10:37 UTC.

Extremely thin, threadlike crescent against blue background.

Youngest possible lunar crescent, with the moon’s age being exactly zero when this photo was taken — at the instant of new moon – 07:14 UTC on July 8, 2013. Image by Thierry Legault.

When the moon is new, it’s most nearly between the Earth and sun for any particular month. There’s a new moon about once a month, because the moon takes about a month to orbit Earth. Most of the time, the new moon passes not in front of the sun, but simply near it in our sky. That’s why, in most months, there’s no solar eclipse.

On the other hand, the moon must be at the new phase in order for a solar eclipse to take place.

The photo of a new moon at the top of this page shows the moon as it passed near the sun on July 8, 2013. There was no eclipse that day; it was an ordinary new moon. New moons typically can’t be seen, or at least they can’t without special equipment and a lot of moon-photography experience. Thierry Legault was able to catch the photo at top – the moon at the instant it was new – because the moon that month passed to one side of the sun, and the faintest of lunar crescents was visible.

Either way – in front of the sun or just near it – on the day of new moon, the moon travels across the sky with the sun during the day, hidden in the sun’s glare.

Some people use the term new moon for a thin crescent moon visible in the west after sunset. You always see these little crescents – which set shortly after the sun – a day or two after each month’s new moon. Astronomers don’t call these little crescent moons new moons, however. In the language of astronomy, this slim crescent is called a young moon.

New moons, and young moons, are fascinating to many. The Farmer’s Almanac, for example, still offers information on gardening by the moon. And many cultures have holidays based on moon phases.

Positions of waxing crescent moon on different days along ecliptic near star Spica.

Start looking for the young moon – a slim crescent visible in the west after sunset – around August 31, 2019. Read more.

Bottom line: When astronomers say the moon is new, they mean it’s crossing the sky with the sun during the day. New moons generally can’t be seen.

Read more: Year’s closest new supermoon on August 30

Read more: What’s the youngest moon you can see?

Read more: 4 keys to understanding moon phases

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Deborah Byrd