Eridanus is a constellation. It is represented as a river; its name is the Ancient Greek name for the Po River. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is the sixth largest of the modern constellations.

Notable features

Stars

At its southern end is the first magnitude star Achernar (α Eri). Achernar is a very peculiar star because it is one of the flattest stars known. Observations indicate that its radius is about 50% larger at the equator than at the poles. This distortion occurs because the star is spinning extremely rapidly.
Another well-known star in Eridanus is Epsilon Eridani, which has been popular in science fiction because it is relatively close and sun-like (see Epsilon Eridani in fiction). It is now known to have at least one extrasolar planet, which is thought to be a gas giant, like Jupiter.

Supervoid

The Eridanus Supervoid is the largest supervoid (an area of the universe devoid of galaxies) discovered . At a diameter of about one billion light years it is much larger than any other known void and represents a challenge for current theories of the origins of the universe to explain. It was discovered by linking a "cold spot" in the cosmic microwave background to an absence of radio galaxies in data of the US National Radio Astronomy Observatory's Very Large Array Sky Survey. There are also suggestions that the void may due to quantum entanglement between our universe and a parallel universe.

Deep sky objects

Eridanus contains the galaxy NGC 1234.

Visualizations

The name Eridanus refers to the Po River, the main river of northern Italy; its association with a river may derive from its shape, that of a very twisty path. In some star maps, Eridanus is depicted as a river flowing from the waters poured by Aquarius; in such maps, Aquarius is visualized as facing Eridanus (requiring a change of angle from the more traditional visualization and the redesigning of how the stars of Aquarius connect, so that the water poured onto the same side as Eridanus).

Mythology

It is connected to the myth of Phaëton, who took over the reins of his father Helios' sky chariot (i.e., the Sun), but didn't have the strength to control it and so veered wildly in different directions, scorching both earth and heaven. Zeus intervened by striking Phaëton dead with a thunderbolt and casting him to earth. The constellation was supposed to be the path Phaëton drove along; in later times, it was considered a path of souls. Since Eridanos was also a Greek name for the Po (Latin Padua), in which the burning body of Phaëton is said by Ovid to have extinguished, the mythic geography of the celestial and earthly Eridanus is complex.

Citations