Unukalhai in the birth chart: the star on the Serpent's neck

Star data

sefstars catalogue, Swiss Ephemeris 2.10.03.

Unukalhai is the brightest star of Serpens, the Serpent, and its Arabic name means "the neck of the snake". Astrological tradition also called it the Serpent's Heart. In the tropical zodiac it stands in the last third of Scorpio. Ptolemy gave the stars of the serpent held by Ophiuchus the nature of Saturn and Mars, and that formula decides how the star is read.

In the sky

Serpens is the only one of the 88 modern constellations split into two pieces. Ophiuchus, the Serpent-bearer, holds the snake in his hands, and his figure lies in the middle: Serpens Caput, the head, is to the west and Serpens Cauda, the tail, to the east. Unukalhai is in the western part, but it marks the neck rather than the head itself, as its name says.

It is an orange giant of spectral class K2, a star that has left the main sequence, grown large and has a cooler surface than the Sun. It is about 74 light-years away, the distance given by the parallax measured by the Gaia space telescope. It is of the second magnitude, so it gives way to the first-magnitude stars in brightness, but it stands out clearly among its neighbours in the sky.

Unukalhai lies about 25° north of the ecliptic. A conjunction with it by longitude is therefore a projection: a planet at the same degree of Scorpio is far from the star in the sky. For stars like this some astrologers prefer parans.

Finding it from Ukraine

Unukalhai is a star of late spring and summer. It stands highest at midnight around 20 May, and in June and July it can be seen in the south in the evening. The handiest guide is Corona Borealis, a small half-circle of stars. From Alphecca, the brightest star of the Crown, Unukalhai lies about 20° almost due south.

From the latitude of Kyiv it climbs to about 46° above the southern horizon at its highest. Being of the second magnitude, it is easy to see outside towns and still visible in city light, though it does not catch the eye.

The name

The name comes from the Arabic Unq al-Hayya, "the neck of the snake". The star-name historian Richard Hinckley Allen also lists the forms Alioth, Alyah and Alyat; he notes that these are not Arabic words and thinks they most probably go back to the constellation's Arabic name al-Hayya, "the snake". The Latin astrological title Cor Serpentis, "the Serpent's Heart", Allen says, certainly belonged to this star.

In Greek the constellation was simply Ophis, "the snake", or the Serpent of Ophiuchus, and Latin writers often called it the Serpent of Aesculapius, the Roman god of healing. Biblical interpreters of the sky, Allen notes, saw in it instead the serpent that tempted Eve.

In China the star, together with a neighbour, was Shuh, named after an old territory: according to Allen, the stars of the Serpent were named in Chinese astronomy after the states. The International Astronomical Union approved Unukalhai as the star's official name in 2016.

Nature according to Ptolemy

Ptolemy does not describe this star on its own. In the first book of the Tetrabiblos he speaks of Ophiuchus and then of the snake in his hands: "those in his serpent, of Saturn and Mars". Unukalhai is the brightest of these stars, so Ptolemy's formula applies to it first of all. Ophiuchus himself gets a different description, Saturn with some Venus, so the snake in his hands carries a harder, Martial formula than the figure holding it.

Saturn stands for pressure, restriction, endurance and long effort. Mars stands for drive, sharpness and a readiness for conflict. Together they describe hardness and persistence, a force that acts stubbornly and not always gently. Read through this pair, the star suggests resolve under difficult conditions, and on its shadow side harshness and a taste for rivalry.

After Ptolemy

Unukalhai is not one of Agrippa's fifteen Behenian stars. Later tradition knows it mainly by its Latin name, the Serpent's Heart, and Allen, as noted above, calls it outright the Cor Serpentis of the astrologers.

In Ptolemy's time the star stood at the end of Libra. It crossed into Scorpio around the fifth century, so all medieval and later tables already place it in that sign.

Conjunctions with planets and angles

Unukalhai is used by conjunction, with an orb of about 1°. It is fainter than the first-magnitude stars and far from the ecliptic, so it weighs less in a chart than they do. Two typical cases:

• Unukalhai with the Sun. Saturn and Mars add steadiness and edge to the Sun: a will that does not give way under pressure and a readiness to go against the current. The same pair also carries a risk of too much hardness; how much of it there really is depends on the overall condition of the Sun.
• Unukalhai on the Ascendant. On the angle that describes manner and first impressions, astrologers read the star's tone as reserve, seriousness and an inner tension that others notice. The rest of the chart decides whether this comes across as composure or as prickliness.

In celebrity charts

Conjunctions within 1° to the planets from the Sun to Saturn and to the chart angles.

• Hillary Clinton: Mercury, orb 0°00′
• JD Vance: IC, orb 0°12′
• Joe Biden: Mercury, orb 0°30′

Find fixed stars in your chart