What’s The Full Strawberry Moon Doing In Ophiuchus?

A pinkish-orange full moon rises alongside the lighthouse at the end of the Duluth Ship Canal in Duluth, Minn. Click to find moonrise times for your town. Credit: Bob King

Ophiuchus. You may wonder what the moon’s doing in a constellation astrologers don’t consider a part of the zodiac. Aren’t there 12 zodiac constellations – one for each month of the year? Well, astrologically yes, but not astronomically. And it’s all because Belgium astronomer Eugene Delporte was tasked nearly a century ago with making sense of the haphazard constellation boundaries in use at the time. More about that in a moment.

Tomorrow night June 12 the Strawberry Moon will rise in the east around sunset. Although your calendar (like mine) may show June 13 as the date of full moon, much of North and South America will see it full the night of the 12th. The moment of maximum fullness occurs at 11:11 p.m. CDT.

Strawberry’s a fitting a name for the June moon as the berries are ripe for picking this time of year.  As if partaking of the berries’ juicy redness, hazy summer skies often color the moon a deep orange or even red at moonrise.

The full moon will shine from Ophiuchus tomorrow night. Thanks to crisp, modern constellation boundaries, the moon spends about one night a month in the constellation. The sun crosses Ophiuchus in the late fall and lingers there for several weeks. Should it be the 13th sign of the zodiac? What do you think? Created with Chris Marriott’s SkyMap software

Ophiuchus (oh-fee-YOO-cuss) the Serpent Bearer represents a man with the snake Serpens (a separate constellation) coiled around his shoulders. To the ancient Greeks he was the god of medicine. The snake represented healing because of its seemingly magical ability to shed its skin, giving it the appearance of being reborn.

Before 1930, the June moon would have cruised from Scorpius to Sagittarius in its monthly trip through the zodiac constellations. Now it spends a night every month in Ophiuchus. In 1925, Eugene Delporte of the Royal Observatory of Brussels proposed the need for clear, universally-accepted constellation boundaries to the International Astronomical Union (IAU).

The full moon rises in Ophiuchus tomorrow evening June 12. Stellarium

Boundaries were vague at the time and depended upon the star atlas you were using. Understandably, this created confusion for astronomers about what was where. Take variable stars – stars whose light isn’t constant but changes over time. Variables are named after the constellation in which they’re found, so for instance, R Leonis is in Leo and U Geminorum in Gemini. As new variables were discovered, astronomers needed to agree to which constellation they belonged. That was only the half of it. What about new comets, novae and other new discoveries? Agreeing on terms is the foundation of communication.

A section of Johann Bode’s early 19th century star atlas featuring the constellations Cygnus and Lyra. If you look closely you’ll see the curvy borders around constellations in fashion until 1930.

The IAU thought it a great idea and put Delporte in charge. He drew up boundaries along existing vertical lines of right ascension and horizontal lines of declination, similar to latitude and longitude on Earth but applied to the sky.

Delporte’s proposal was approved in 1928 and written up in 1930, and that’s why the moon will linger in the Serpent Bearer tonight. Happy gazing!

7 Responses

  1. caralex

    My sun sign is ‘really’ Ophiuchus, not Sagittarius. I love confounding those serious about astrology by telling them that!

  2. Troy

    Interesting, I see from your chart that the constellation boundary should have been made to keep the sun, moon, and planets in the zodiac. The 13th sign is actually Ariadne (the spider). I read a story about it, but forgot the details.

Comments are closed.