Universe Guide

Eridanus, River Eridanus Constellation

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 31 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.

There are 32 Extrasolar Planets (Exoplanets) in this constellation that are detailed on this site. There is a dedicated page for exoplanets in Eridanus.

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.

Distance to Eridanus

You can't just go to one location and arrive at the constellation because the constellation is made up of stars at different locations and different distances. The nearest main star in the constellation is at a distance of 10.49 light years and the furthest main star is a distance of 1,475.85 light years. The average distance to the main stars is 254.13 light years.

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, Eridanus's 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, Eridanus's 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.

How to Find and View Eridanus in the Night Sky

Northern Hemisphere

Eridanus is never fully visible in the Northern hemisphere, in London at least. You will never see the southern tip of it, that is Achernar. You are able to see the Witch-Head Nebula, a reflection nebula that is lit up by radiation from Rigel in neighbouring Orion constellation. The most southern star would be G Eridani, anything more south, you will not be able to see in London. If you head south, you'll have better luck at seeing the southern stars including the Alpha Star.

Southern Hemisphere

The Southern Hemisphere has a good view of the constellation and is fully visible from November to April time. Eridanus lays across the sky. It fully disappears from May until September when it slowly begins to appear on the horizon led by its Alpha star, Achernar.

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
Nu Eridanids24th Sept  
upsilon Eridanids16th January  
Eta Eridanids3 Aug- 14 Aug09-AugAzha
November epsilon Eridanids23rd November  

List of Main Stars in Eridanus

The following list contains the stars that make up the constellation. For a larger list of stars in the entire constellation area, please visit the For a list of named stars, that is stars that don't start HD or HIP, please visit Eridanus Star List page.

NameBayerDistance (Lt.Yr.)Right AscensionDeclinationSpectral TypeColour
AchernarAlpha Eridani139.4501h 37m 42.75-57d 14` 12.0B3VpBlue/White
CursaBeta Eridani89.3605h 07m 51.03-05d 05` 10.5A3IIIvarWhite
ZaurakGamma Eridani203.3403h 58m 01.73-13d 30` 29.7M1IIIb Ca-1Red
RanaDelta Eridani29.4903h 43m 14.96-09d 45` 54.7K0IVOrange
RanEpsilon Eridani10.4903h 32m 56.42-09d 27` 29.9K2VOrange
ZibalZeta Eridani109.7503h 15m 50.03-08d 49` 11.4A5mWhite
AzhaEta Eridani136.5302h 56m 25.60-08d 53` 51.4K1III-IVOrange
Iota EridaniIota Eridani150.6502h 40m 39.93-39d 51` 19.1K0IIIOrange
Kappa EridaniKappa Eridani508.0402h 26m 59.10-47d 42` 13.8B5IVBlue/White
Mu EridaniMu Eridani521.8604h 45m 30.14-03d 15` 16.6B5IVBlue/White
Nu EridaniNu Eridani675.2904h 36m 19.14-03d 21` 08.8B2III SBBlue/White
BeidOmicron1 Eridani121.7004h 11m 51.93-06d 50` 16.0F2II-IIIYellow/White
Pi EridaniPi Eridani481.0703h 46m 08.50-12d 06` 06.2M1IIIRed
Tau6 EridaniTau6 Eridani57.4903h 46m 50.99-23d 14` 54.4F3/F5VYellow/White
Tau7 EridaniTau7 Eridani250.8903h 47m 39.62-23d 52` 29.3A1VWhite
Tau8 EridaniTau8 Eridani377.0703h 53m 42.68-24d 36` 44.0B5VBlue/White
Tau9 EridaniTau9 Eridani327.4703h 59m 55.48-24d 00` 58.5Ap SiWhite
Tau4 EridaniTau4 Eridani304.5403h 19m 30.97-21d 45` 28.6M3/M4IIIRed
Tau1 EridaniTau1 Eridani46.3802h 45m 05.98-18d 34` 21.5F5/F6VYellow/White
Tau3 EridaniTau3 Eridani88.6303h 02m 23.59-23d 37` 27.6A4VWhite
Upsilon1 EridaniUpsilon1 Eridani127.0604h 33m 30.63-29d 45` 57.0K0IIIOrange
Upsilon4 EridaniUpsilon4 Eridani177.9404h 17m 53.62-33d 47` 54.0B9VBlue/White
BeeminUpsilon3 Eridani296.2404h 24m 02.17-34d 01` 01.2K4IIIOrange
Phi EridaniPhi Eridani153.7102h 16m 30.50-51d 30` 43.6B8IV-VBlue/White
Chi EridaniChi Eridani58.2201h 55m 56.83-51d 36` 34.5G5IVYellow
S Eridani290.1804h 59m 55.71-12d 32` 13.9F0VYellow/White
G Eridani209.8903h 49m 27.28-36d 12` 00.4G8IIIYellow
H Eridani184.2703h 42m 50.12-37d 18` 48.0K2IIICN...Orange
15 Eridani255.4103h 18m 22.10-22d 30` 40.1K0IIIOrange
Y Eridani1475.8502h 05m 34.16-57d 08` 39.0MeRed
82 Eridani19.7103h 19m 53.22-43d 04` 17.6G8VYellow

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 Count31
Messier Deep Space Object Count0
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 1234Lenticular Galaxy-07 50 43.3903 09 39m 000
NGC 1300Barred Spiral Galaxy61,000,000-19:24.4103h 19h 41m 1
NGC 1309Spiral Galaxy100,000,000-15 23 47.703 22 5m 69
NGC 1332Galaxy in a Pair of Galaxies-21 20 07.3303 26 17m 321
NGC 1427AIrregular Galaxy50,000,000-35:37:17.743 40 9m 41
NGC 1627Galaxy-04:53:8052704h 37h 38m 01515
NGC1600Galaxy 200,000,000-05 05 09.9704 31 39m 858

Comments and Questions

There's no register feature and no need to give an email address if you don't need to. All messages will be reviewed before being displayed. Comments may be merged or altered slightly such as if an email address is given in the main body of the comment.

You can decline to give a name which if that is the case, the comment will be attributed to a random star. A name is preferred even if its a random made up one by yourself.

This website is using cookies. More info. That's Fine