On Friday, May 19, the only “dark moon” of the year will rise in the sky – and there will be precisely nothing to see. That’s because Earth’s natural satellite will drift right into the sun’s glare, signaling a new moon. So why this mysterious name?
The term “dark moon” has several meanings – none of them astronomical but all of them only occur once every few years.
The definition that best fits this month’s event is a “seasonal black moon” – the third new moon in a season with four new moons. This is something that only happens every 33 months or so, according to Timeanddate.com (opens in a new tab).
Each astronomical season on Earth begins and ends with a solstice and a equinox. This current season, spring in the northern hemisphere and autumn in the southern hemisphere, began with the vernal equinox on March 20, 2023. Importantly, it was also the date of a new moon. As a new moon occurs every 29.5 days – the time it takes for the moon to complete an orbit around Earth – there is enough time for three more new moons to occur before the summer solstice. of June 21, 2023.
The dates for the new moon this season are: Tuesday, March 21; Thursday, April 20; Friday May 19; and Sunday, June 18. This third new moon is the “dark moon” of this month.
The term dark moon is also used to describe other distinct lunar events. Just as a blue moon is the second full moon in the same calendar month – also made possible by the moon’s 29.5-day Earth orbit – the second new moon in the same calendar month is sometimes called a black moon. This can happen approximately every 32 months, depending Almanac.com (opens in a new tab).
The black moon can also be used to describe the rare occurrence of a month without a new moon or a full moon, according to Timeanddate.com. This can only happen in February – the only month short enough to start and end between two new moons or two full moons. It’s something that happens once every five to 10 years, according to Almanac.com.
Although a dark moon is not something you can see because the part of the moon facing us is in shadow, it means the night sky is free of moonlight which makes them perfect for stargazing. On the evening after the new moon – May 19, 20 and 21 – look west after sunset and you will see a thin crescent moon emerging after the only dark moon of 2023.