Stellar System
Delta Capricorni is an eclipsing binary star system similar to Algol, with an orbital period of 1.022768 days and an inclination close to the line of sight from the Earth. The peak apparent visual magnitude of the pair is 2.81. During an eclipse of the primary, this magnitude drops by 0.24. When the primary is eclipsing the secondary, the magnitude decreases by 0.09.
The primary component, Delta Capricorni A, has an overall stellar classification of A7m III, indicating that it is a giant star that has exhausted the supply of hydrogen at its core. More specifically, this is a chemically-peculiar Am star with a spectral type of kA5hF0mF2 III under the revised MK system. This notation indicates that the K-line matches the temperature of an A5 star, the hydrogen spectral type matches an F0 star, and the metallic absorption lines match an F2 star.
In the past this star was suspected of being a Delta Scuti variable, which is rare for an Am star. This categorization was brought into question during observations in 1994 and it is most likely not a variable star. Compared to the Sun, the primary has double the mass and nearly twice the radius. It is rotating rapidly with a projected rotational velocity of 105 km s–1. (This rotation rate is synchronous with the orbital period.) Note that it is unusual for an Am star to have such a high rotational velocity. The outer envelope of the star is radiating energy at an effective temperature of 7,301 K, giving it the white-hued glow of an A-type star. The secondary component is a type G or K star with around 90% of the mass of the Sun.
There are two optical companions. A sixteenth magnitude star is one arcminute away, while the thirteenth magnitude star D is two arcminutes away from the system.
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