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Eridanus, River Eridanus Constellation Facts and Mythology

Eridanus Constellation Star Map

Eridanus (Pronounciation:Iri-dan-us, Abbrev:Eri, Latin:Eridani) is a constellation, one of 88 constellations that the night sky is divided into. The sky is not divided up equally between the constellations. Eridanus takes up 1137.919 sq. degrees of the night sky which equates to 2.76% of the night sky. Eridanus is the 6th largest in terms of size in the night sky.

The constellation name means River Eridanus . The constellation is one of the original constellations that was devised by the Ancient Greco-Egyptian astronomer Ptolemy who lived between 90 A.D. and 168 A.D.

There are 35 stars that make up the main constellation. The hipparcos satellite scanned and detailed 2759 stars. There are 128 stars that can be seen with the naked eye in the constellation on a very clear night sky.

Eridanus is not a member of the Zodiac group of twelve constellations that appear when the Sun sets. Eridanus is a southern hemispheric constellation which means it can't be seen easily or at all from the northern hemisphere.

The distance to Eridanus is not calculable because all the stars that make up the constellation are at various distances. The best answer for distance to Eridanus is to calculate the average distance of the stars.

There are 32 Extrasolar Planets (Exoplanets) in this constellation that are detailed on this site. There is a dedicated page for exoplanets in Eridanus. For a list of named stars, that is stars that don't start HD or HIP, please visit Eridanus Star List Page.

There are no deep space objects that were identified by Charles Messier in this constellation. There are 2 non-Messier deep space objects that are covered on this site and the list is below.

The image at the top right of this page was generated using Night Vision, a free to use and download application by Brian Simspon.

Eridanus Star Facts

The caveat of these stars are that they are catalogued on this site. If you know of a star that is nearer or further then do let me know in the comments and I'll add it to the site. The stars mentioned are from the Hipparcos catalogue or have been added because of their special status.

HIP 13391, Furthest Star

The furthest star that is located in the constellation is HIP 13391 and it is 326163.3 light years away from the Sun. The furthest figure is derived from either the 1997 or 2007 Hipparcos star catalogue parallax figure and it has been known to produce distances that are wrong.

GZ Eridani, Dimmest Visible Star

The dimmest star that can be seen in Eridanus with the naked eye is GZ Eridani. The dim star has an apparent magnitude of 6. The dimmest star that a person is able to see with their naked eye is 6.0 magnitude based on the table in the reference. Ref: University of Michigan.


Achernar is at the southern end of the river and is as far as you can get from the the second brightest, Cursa which is also known as Beta Eridani. The most interesting thing about the star is its shape. Achernar is not spherical like most star, its has flattened out, caused by its rotation and its pull by other stars.


At the very top of the star is Cursa, the second brightest star in the constellation. Its as far as you can get from the brightest star in a single constellation. It is in the Northern hemisphere whereas Achernar is in the southern.


40 Eridani or Keid which is easier to remember is best remembered amongst trekkies for being the home star for Vulcan. The star was chosen by Gene Roddenberry. The star is a multi-star system and any planet would have a two star sky line much like Tatooine in Star Wars, the "rival" space franchise. At present, no planets have been spotted orbiting the star.

Sadira / Ran

18 Eridani is one of the closest stars to Earth that has exoplanets orbiting it. For a long time, 18 Eridani was also referred to as Sadira but when the IAU ran a competition, they ignored the name and chose Ran instead for its name.

Eridanus Mythology

Eridanus, the river was where Phaethon fell into when he was knocked out of his chariot basket. Phaethon had taken his father Helios' chariot and rode it across the skies both too high and too lower. As it was scaring the people below, Zeus threw fire bolts at the chariot to stop him. The chariot stopped but Phaethon fell out and into the river.

Meteor Showers Radiating from Eridanus

There are 14 Meteor Showers that occur during the year within this constellation based on information gathered from Adam Mickiewicz University (Poland). The list below are major ones and which I have a date period for.

NameActivityPeak ActivityClosest Star
Eta Eridanids3 Aug- 14 Aug09-AugAzha

Eridanus Facts

Is a Zodiac Sign No
Brightest StarAchernar
Area1137.919 sq. deg.
Percentage of Night Sky2.76%
Size Position6th
Hemisphere Southern
Site Exoplanet Count32
Meteor Shower Count14
Nearest StarRan
Nearest Star with Exoplanet(s)Sadira
Brightest StarAchernar
Dimmest StarGZ Eridani
Furthest StarHIP 13391
Bright Star Count128
Hipparcos Star Count2759
Main Star Count35
Messier Deep Space Object Count0
*Non-Messier Deep Space Object Count2
Bordering / Neighbouring / Surrounding ConstellationsTaurus

*Note: The number of Non-Messier Deep Space Object Count relates to how many are covered on this site not how many there are.

List of Deep Space Objects (Galaxies, Nebulas, Supernovas, etc) in Eridanus

NameTypeDistanceDeclinationRight Ascension
NGC 1300Barred Spiral Galaxy61-19:24.4113h 19m 41s

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