Acubens in the birth chart: the star in the Crab's claw

Star data

sefstars catalogue, Swiss Ephemeris 2.10.03.

Acubens is the star in the southern claw of the constellation Cancer, the Crab. In the tropical zodiac it no longer stands in Cancer: it sits in the middle of Leo. Ptolemy gives the stars in the Crab's claws the nature of Saturn and Mercury, a sober and thoughtful mix, quite unlike the fire sign the star now stands in.

In the sky

Cancer is the least conspicuous of the zodiac constellations, as Allen already noted in 1899, and Acubens is a modest star even by its standards. It carries the first Greek letter, alpha, yet it is not the brightest star of the Crab: Beta Cancri, about three quarters of a magnitude brighter, takes that place. As with the twins of Gemini, Bayer's letters do not follow brightness here.

Acubens lies about 5° south of the ecliptic. That is close enough for the Moon, whose path wanders up to about 5° either side of the Sun's, to pass in front of it now and then, and observers photograph these occultations. For chart work this means that a conjunction with Acubens by zodiacal degree is close to a real meeting in the sky, though not as close as with Regulus, which lies almost on the ecliptic.

What kind of star it is

Acubens is a white star of spectral class A, about 180 light-years away according to the Gaia space telescope. Its spectrum shows an unusual mix of chemical elements, which places it among the chemically peculiar stars of its class. A telescope shows a faint companion close by: Richard Hinckley Allen in 1899 gave the separation as about 11 arcseconds.

Finding it from Ukraine

Acubens is a star of late winter and spring evenings. Cancer fills the dim stretch of sky between the bright Twins of Gemini and the Sickle of Leo, and the easiest landmark in it is the Beehive, a star cluster that looks like a small pale cloud to the naked eye on a dark night. Acubens is the faint star about 9° to the south-east of the Beehive, towards the head of Hydra.

From the latitude of Kyiv the star climbs to about 51° above the southern horizon, so it is high enough to see from anywhere in the country, but it needs a sky free of city light. At fourth magnitude it vanishes in a bright town sky long before brighter stars do. The Sun passes Acubens in early August, and for some weeks around that date the star is lost in its glare.

The name

The name comes from the Arabic al-zubana, "the claw". Allen records that the Alfonsine Tables called the claws Acubenae and attributed the word to the Chaldaeans, but the word is Arabic, not Chaldaean. The same Arabic word was also used for the claws of Scorpius, which is why a similar name appears in the other half of the zodiac. Another name sometimes given to the star, Sartan, comes from the Arabic word for the whole Crab.

According to the IAU Working Group on Star Names, Arabic versions of Ptolemy's Tetrabiblos used this word for both claw stars, alpha and iota Cancri. In 2016 the International Astronomical Union approved Acubens as the official name of alpha Cancri.

Nature according to Ptolemy

In the first book of the Tetrabiblos, Ptolemy says that the stars in the Crab's claws are "the same as Saturn and Mercury". He does not single out Acubens; it shares this nature with the star of the other claw. The overview explains how such planetary comparisons are read.

Saturn stands for limits, patience, caution and endurance, and also for weight and delay. Mercury stands for the mind, speech, calculation, trade and skill with the hands. Together they describe a careful, slow and precise kind of thinking: the mind that checks, plans and holds on. The darker side of the same pair is worry, a habit of suspicion and a tendency to brood.

It is worth noticing the company the star keeps. The Crab's other stars in Ptolemy's list all carry Mars, mixed with Mercury, the Moon or the Sun, and Acubens now stands in Leo, in a stretch of the zodiac associated with display and warmth. Its own nature stays the cool one of its constellation; the sign only says where it stands.

Conjunctions with planets and angles

Acubens is read by conjunction within an orb of about 1° (orb), tighter contacts counting for more. Because it is a faint star, many astrologers give it less weight than a first-magnitude star in the same position. Two typical cases show how tradition reads it.

• Mercury on Acubens. Mercury is half of the star's own nature, so the contact strengthens Mercury's themes in a Saturnine key: thoroughness, a taste for detail, patient study and a sceptical mind. Astrologers read the same contact as a tendency to overthink and to hold on to worries.
• Acubens on the Ascendant. On the Ascendant a star colours the manner. Here it suggests reserve and caution with strangers, and a person who weighs words before speaking.

The rest of the chart decides how much of this shows. A Mercury already in hard aspect to Saturn will carry the star's tone more strongly than a Mercury in easy contacts.

In celebrity charts

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

• Giorgia Meloni: Ascendant, orb 0°00′
• Shakira: Saturn, orb 0°05′
• Marine Le Pen: Sun, orb 0°09′

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