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EVERY so often, people who are into astrology discover Ophiuchus, which is often referred to as the 13th zodiacal constellation. Sometimes, they will be surprised a new sign of the zodiac has been invented, but in reality, Ophiuchus (pictured above) is a constellation that has been known about ever since ancient Greek astronomers named it after a serpent bearer. This month is a great time to look for it around the world.

Ophiuchus sits alongside Sagittarius and Scorpius, near the bright centre of the Milky Way. With its position just to the side of the Milky Way’s band, it is much fainter than its neighbours. The constellation is visible around the world, but viewers in the southern hemisphere will have a better chance of seeing it this month, since the nights are longer and darker there this time of year.

To find Ophiuchus in the northern hemisphere, look south-east as soon as it is dark. First, identify Antares, a reddish star in the head of Scorpius. At dusk in this region of the globe, Antares is the brightest star near the southern horizon, and it sits next to a line of three fainter stars. Then, to the left of Antares, find Sabik, the brightest star in Ophiuchus. The rest of Ophiuchus, which is shaped like a large pentagon, is directly above Sabik.

This method will work whenever you look, but on 4 June in the northern hemisphere, the almost-full moon will rise around 11pm and Ophiuchus will appear directly above it in the sky.

In the southern hemisphere, if you have a clear view of the Milky Way you will be able to see all of Scorpius, easily recognised by the long arc of its tail and the three stars in a line at its head. It will be in the east and will cross the band of the Milky Way. It is best to wait an hour or two after sunset, then look to the east. Directly above the horizon you will see Antares, with Sabik below it. The rest of Ophiuchus lies down and to the north. Again, on 4 June, the moon will form a triangle with Antares and Sabik.

The question of whether Ophiuchus is a zodiacal constellation depends on how exactly these constellations are defined. Generally, the zodiacal constellations are those that cross the ecliptic, the path the sun appears to trace in the sky, and Ophiuchus crosses the ecliptic just as much as any of the other zodiacal constellations.

Some astronomers say the zodiacal constellations are those through which planets pass. In that case, we would have to include more constellations because the paths of the planets cover a larger area of the sky. According to John Mosley, formerly at Griffith Observatory in California, there are 21 such constellations.

Whether or not it is embraced by the astrology community, Ophiuchus is a lovely constellation, and it deserves to be better known.

Abigail Beall is a features editor at 91av and author of The Art of Urban Astronomy. @abbybeall

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