Deneb Algedi

Deneb Algedi is Delta Capricorni, an eclipsing binary at about 39 light years whose components periodically pass in front of one another, dimming the pair slightly, and it is the brightest star of Capricornus. Its name, from the Arabic dhanab al-jady, means the tail of the goat, or of the sea-goat, the strange composite creature, half goat and half fish, that the constellation depicts, a figure going back to Mesopotamian tradition. It marks the fishy tail with which the climbing goat of the zodiac ends.

Deneb Algedi's eclipses are shallow, a partial rather than total blocking of one star's light by the other, similar in kind to Algol's though smaller in amplitude, and the system is close enough, at under forty light years, that its orbital and physical parameters are unusually well determined compared with most of the other eclipsing pairs named in this catalogue. Deneb Algedi's status as Capricornus's brightest star despite the faintness of the constellation as a whole reflects how dim the sea-goat figure is overall, one of the less conspicuous members of the zodiac to the naked eye. Its shallow, precisely timed eclipses have made Deneb Algedi a useful calibration target for photometric instruments being tested against a known, well-characterised variable.

Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with The Arabs and the StarsPaul Kunitzsch

The tradition gives Deneb Algedi the nature of Jupiter with Saturn, and Robson reads it as a mixture of beneficence and sorrow, legal and public position on the one hand, quiet grief and reversal on the other, the Jovian and Saturnine strands pulling against each other. It is the last of Agrippa's fifteen Behenian stars, the set singled out in Renaissance magic for talismans, where it is paired with the stone chalcedony and with the herbs marjoram and sorrel. That makes it, unusually, one of the few stars with a documented early-modern stone-and-herb correspondence rather than a modern invention, a genuine link between the fixed-star lore and the talismanic tradition of the sixteenth century.

Deneb Algedi's recorded Agrippa correspondences, chalcedony and the herbs marjoram and sorrel, close out the fifteen Behenian stars in the traditional ordering, which generally runs from Aldebaran through the zodiacal and circumpolar bright stars to this last entry in Capricornus; three of the fifteen, this star, Procyon and Alphecca, happen to fall among the articles gathered in this set of tables, a useful reminder of how much of the Behenian scheme threads through stars otherwise treated only for their constellation position.