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Eridanus constellation

Eridanus is a constellation of the southern sky. Its brightest star is Achernar. Visibility at mid-northern latitudes (52° N): only partly visible — its southern part never rises above the horizon.

  • Winterbest seen
  • Achernarbrightest star, magnitude 0.5
  • EriEridanus
Show on the sky map
The constellation Eridanus in the starry sky: its figure and its bright stars Sirius, Canis Major — magnitude −1.4. Open on the sky mapCanopus, Carina — magnitude −0.6. Open on the sky mapRigel, Orion — magnitude 0.2. Open on the sky mapAchernar, Eridanus — magnitude 0.5. Open on the sky mapAchernarAdhara, Canis Major — magnitude 1.5. Open on the sky mapAlnilam, Orion — magnitude 1.7. Open on the sky mapAlnitak, Orion — magnitude 1.7. Open on the sky mapRegor, Vela — magnitude 1.8. Open on the sky mapWezen, Canis Major — magnitude 1.8. Open on the sky mapMirzam, Canis Major — magnitude 2.0. Open on the sky mapDiphda, Cetus — magnitude 2.0. Open on the sky mapSaiph, Orion — magnitude 2.1. Open on the sky mapNaos, Puppis — magnitude 2.2. Open on the sky mapMintaka, Orion — magnitude 2.3. Open on the sky mapAnkaa, Phoenix — magnitude 2.4. Open on the sky mapAludra, Canis Major — magnitude 2.5. Open on the sky mapArneb, Lepus — magnitude 2.6. Open on the sky mapPhact, Columba — magnitude 2.6. Open on the sky mapπ Puppis — magnitude 2.7. Open on the sky mapHatysa, Orion — magnitude 2.8. Open on the sky mapCursa, Eridanus — magnitude 2.8. Open on the sky mapCursaNihal, Lepus — magnitude 2.8. Open on the sky mapα Hydri — magnitude 2.9. Open on the sky mapAcamar, Eridanus — magnitude 2.9. Open on the sky mapAcamarτ Puppis — magnitude 2.9. Open on the sky mapZaurak, Eridanus — magnitude 3.0. Open on the sky mapZaurakRana, Eridanus — magnitude 3.5. Open on the sky mapRanaBeemim, Eridanus — magnitude 3.5. Open on the sky mapφ Eridani — magnitude 3.6. Open on the sky mapχ Eridani — magnitude 3.7. Open on the sky mapτ⁴ Eridani — magnitude 3.7. Open on the sky mapRan, Eridanus — magnitude 3.7. Open on the sky mapTheemin, Eridanus — magnitude 3.8. Open on the sky mapSceptrum, Eridanus — magnitude 3.9. Open on the sky mapAzha, Eridanus — magnitude 3.9. Open on the sky mapν Eridani — magnitude 3.9. Open on the sky mapBeemim, Eridanus — magnitude 4.0. Open on the sky mapμ Eridani — magnitude 4.0. Open on the sky mapBeid, Eridanus — magnitude 4.0. Open on the sky mapτ³ Eridani — magnitude 4.1. Open on the sky mapι Eridani — magnitude 4.1. Open on the sky mapg Eridani — magnitude 4.2. Open on the sky mapτ⁶ Eridani — magnitude 4.2. Open on the sky mapκ Eridani — magnitude 4.2. Open on the sky mapλ Eridani — magnitude 4.3. Open on the sky mape Eridani — magnitude 4.3. Open on the sky mapτ⁵ Eridani — magnitude 4.3. Open on the sky mapf Eridani — magnitude 4.3. Open on the sky map54 Eridani — magnitude 4.3. Open on the sky mapω Eridani — magnitude 4.4. Open on the sky mapπ Eridani — magnitude 4.4. Open on the sky mapKeid, Eridanus — magnitude 4.4. Open on the sky mapw Eridani — magnitude 4.5. Open on the sky mapτ¹ Eridani — magnitude 4.5. Open on the sky mapBeemim, Eridanus — magnitude 4.5. Open on the sky mapy Eridani — magnitude 4.6. Open on the sky maph Eridani — magnitude 4.6. Open on the sky map N ↑← E
North is up, east is left — this is how the constellation looks in the sky. Click a star to open it on the sky map.

How to find the constellation Eridanus

Use its brightest star as a guide: Achernar (magnitude 0.5). In December around 22:00 it is highest above the southern horizon — the center of the figure rises to about 12°. Its southern part never rises at mid-northern latitudes (52° N) — the whole constellation can be seen from further south.

LocationVisibility
40° NMadrid, New York, Beijingonly partly visible — its southern part never rises above the horizon
52° NLondon, Berlin, Warsawonly partly visible — its southern part never rises above the horizon
60° NOslo, Helsinki, Saint Petersburgonly partly visible — its southern part never rises above the horizon

Bright stars of the constellation

StarMagnitudeColorDistance
Achernarα Eridani 0.5blueabout 139 light years
Cursaβ Eridani 2.8bluish white—
Acamarθ¹ Eridani 2.9bluish white—
Zaurakγ Eridani 3.0orange—
Ranaδ Eridani 3.5orange—
Beemimυ⁴ Eridani 3.5blue—
φ Eridani 3.6blue—
χ Eridani 3.7yellow—
τ⁴ Eridani 3.7red—
Ranε Eridani 3.7yellow—
Theeminυ² Eridani 3.8orange—
Sceptruml Eridani 3.9orange—

Magnitude is a measure of a star’s brightness: the smaller the number, the brighter the star; on a dark night the naked eye can see stars down to magnitude 6.

Questions

How do you find the constellation Eridanus in the sky?

Use its brightest star as a guide: Achernar (magnitude 0.5). In December around 22:00 it is highest above the southern horizon — the center of the figure rises to about 12°. Its southern part never rises at mid-northern latitudes (52° N) — the whole constellation can be seen from further south.

When is the best time of year to observe the constellation Eridanus?

In winter: in December around 22:00 the constellation is highest above the horizon. Two or three months earlier it can be seen before dawn, two or three months later only in the early evening, and half a year later it is in the sky during the day, near the Sun, and can’t be seen.

What is the brightest star in the constellation Eridanus?

Achernar: magnitude 0.5, blue. Distance: about 139 light years.

How many stars are there in the constellation Eridanus?

With the naked eye on a perfectly dark night — with no light pollution and no Moon — you can see about 128 stars in the constellation (brighter than magnitude 6, within the constellation’s boundaries). In a city far fewer: usually only the stars of its figure.

Winter constellations

Find it in the sky tonightA sky map over your city: where the constellation Eridanus is now and when it will rise.
Open the sky map