news sciences: Is Ophiuchus a constellation or a sign?

The constellation Ophiuchus above the red supergiant star Antares in the July evening sky. — If you’re in the Northern Hemisphere, look southward on July or August evenings for mighty Ophiuchus the Serpent Bearer.

The forgotten constellation

Ophiuchus the Serpent Bearer is sometimes called the 13th or forgotten constellation of the zodiac. That’s because the sun passes in front of Ophiuchus from about November 30 to December 18 each year. And yet no one ever says they’re born when the sun is in Ophiuchus.

Ophiuchus is a constellation – not a sign – of the zodiac.

What are astrological signs? The 12 signs of the tropical zodiac represent equally-sized, 30-degree divisions of the sky. That’s why, for example, the sun resides in front of each zodiacal sign for a precise interval of about a month. Meanwhile, the sun is in front of the constellations for varying amounts of time, for example, in front of the constellation Virgo for about 1 1/2 months and in front of constellation Scorpius for about a week.

What are astronomical constellations? The ancient stargazers picked out patterns among the stars, named them, and associated them with legends and myths. Early in the 20th century, the International Astronomical Union (IAU) agreed on official constellation borders. The constellations vary in size and have many different shapes. The constellations of the zodiac are those in which the sun – and moon and planets – all travel. For as long as anyone can remember, we’ve had 12 constellations of the zodiac. Their names are the same (approximately) as the 12 signs of the zodiac.

If include Ophiuchus – which also holds the sun within its borders for part of every year, too – there are 13 constellations of the zodiac.

Antique color etching of old bald bearded man in ancient Greek garb holding a long snake. — Ophiuchus in Urania’s Mirror, a boxed set of 32 constellation cards first published in 1824. Image via www.ianridpath.com.

Ophiuchus a short hop north of Antares

You can see Ophiuchus the Serpent Bearer on these July nights. Its stars are faint, and you’ll need a dark sky. Look for Ophiuchus in the direction south at nightfall from the Northern Hemisphere. From the Southern Hemisphere, look more overhead around mid-evening.

The bright red star Antares in the constellation Scorpius the Scorpion can help you find Ophiuchus. Look for Ophiuchus a short hop to the north of Antares.

Ophiuchus’ brightest star – the 2nd-magnitude star called Rasalhague – highlights the head of Ophiuchus. See Rasalhague in the Ophiuchus chart below. Rasalhague is nowhere near as bright as Antares, though.

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Star chart with black stars on white showing constellation Ophiuchus. — Ophiuchus the Serpent Bearer, via Wikimedia Commons.

Ophiuchus, Snake venom, and access to immortality

On sky maps, Ophiuchus the Serpent Bearer is depicted as holding Serpens the Serpent, which is considered a separate constellation. According to ancient Greek star lore, Ophiuchus is Asclepius, the physician who concocted a healing potion from the Serpent’s venom, mixing it with the Gorgon’s blood and an unknown herb. This potion gave humans access to immortality, until the god of the underworld appealed to Zeus to reconsider the ramifications of the death of death.

Even today, the Staff of Asclepius – the symbol of the World Heath Organization – pays tribute to the constellation Ophiuchus the Serpent Bearer.

Bottom line: Will you see faint Ophiuchus, the overlooked zodiacal constellation, tonight?

Dates of sun’s entry into each constellation of the zodiac

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