The brightest star in Capricornus is δ Capricorni, also called Deneb Algedi, with a magnitude of 2.9, located 39 light-years from Earth.

Like several other stars such as Denebola and Deneb, it is named for the Arabic word for "tail or end" (deneb) and “young goat / kid” (al-gedi); its traditional name means "tail to head” or “back to the beginning", which could be related to the Ouroboros or Janus since the zodiac relates to January.

Also called Algedi or Giedi, the traditional names of α Capricorni come from the Arabic word for "the kid", which references the constellation's mythology.

Messier 30 is a globular cluster located 1 degree south of the galaxy group that contains NGC 7103.

At a distance of 30,000 light-years, it has chains of stars extending to the north that are resolvable in small amateur telescopes.

The face-on spiral galaxy is experiencing abnormally high rates of star formation, indicating that it is interacting with one or both members of the group.

[3] The planet Neptune was discovered by German astronomer Johann Galle, near Deneb Algedi (δ Capricorni) on 23 September 1846, as Capricornus can be seen best from Europe at 4:00AM in September (although, by modern constellation boundaries established in the early 20th century CE, Neptune lay within the confines of Aquarius at the time of its discovery).

Despite its faintness, the constellation Capricornus has one of the oldest mythological associations, having been consistently represented as a hybrid of a goat and a fish since the Middle Bronze Age, when the Babylonians used MULSUḪUR.MAŠ "The Goat-Fish" as a symbol of their god Ea.

[7][6] In Greek mythology, the constellation is sometimes identified as Amalthea, the goat that suckled the infant Zeus after his mother, Rhea, saved him from being devoured by his father, Cronos.

[8] Capricornus is also sometimes identified as Pan, the god with a goat's horns and legs, who saved himself from the monster Typhon by giving himself a fish's tail and diving into a river.

In Chinese astronomy, constellation Capricornus lies in The Black Tortoise of the North (北方玄武; Běi Fāng Xuán Wǔ).