Eridanus constellation: how to find it, when to see it and what is in it
In short
Eridanus (Eri) is a equatorial constellation covering 1,138 square degrees, number 6 of 88 by size. Its brightest star is Achernar, a blue-white main-sequence star, magnitude 0.5. It is best seen in the evening in January. Over London it stays low — you need an open southern horizon. Its neighbours in the sky: Caelum, Cetus, Fornax, Horologium, Hydrus, Lepus, Orion, Phoenix, Taurus.
Area: 1,138 square degrees, 6 of 88 · Neighbours: Caelum, Cetus, Fornax, Horologium, Hydrus, Lepus, Orion, Phoenix, Taurus · Updated 10 October 2026
How to find Eridanus
- 1
When to look
The best time is in January in the evening: in the south, around 20:11.
- 2
Use the neighbours
Find it from the neighbouring constellations: Caelum, Cetus, Fornax, Horologium.
- 3
Brightest stars
The brightest stars of the figure: Achernar (0.5ᵐ), Cursa (2.8ᵐ), Acamar (3.2ᵐ).
When it is visible over London
| Month | Where and when | Conditions |
|---|---|---|
| January — february | in the south, around 20:11 | low, needs an open horizon |
| March — august | — | not visible, behind the Sun |
| September — december | in the south, around 05:13 | low, needs an open horizon |
Stars of the constellation
| Star | What it is | Magnitude |
|---|---|---|
| Achernar · α Eri | blue-white main-sequence star | 0.5ᵐ |
| Cursa · β Eri | white giant | 2.8ᵐ |
| Acamar · θ¹ Eri | white giant | 3.2ᵐ |
| Rana · δ Eri | orange subgiant | 3.5ᵐ |
| φ Eri | blue-white main-sequence star | 3.6ᵐ |
| υ⁴ Eri | blue-white main-sequence star | 3.6ᵐ |
| τ⁴ Eri | red giant | 3.7ᵐ |
| χ Eri | yellow giant | 3.7ᵐ |
Eridanus FAQ
When is the best time to see Eridanus?
Where is Eridanus in the sky?
What is the brightest star in Eridanus?
Neighbouring and other constellations
Related
Constellation lines: Stellarium, CC BY-SA · star names: IAU WGSN, CC BY 4.0