Constellation · Eri
Eridanus
The River
A long, winding constellation that begins near Rigel in Orion and ends at the bright southern star Achernar.
Magnitude 0.45
Highest in the sky at 9 pm local time (winter in the northern hemisphere)
Latitudes where every part of it rises above the horizon at some time of year
The whole sky covers about 41,253 square degrees
Stars brighter than about magnitude 6, the naked-eye limit under dark skies
Named stars in Eridanus
Brightest first. A lower magnitude means a brighter star.
- Achernar (Alpha Eridani)mag 0.45
- Cursa (Beta Eridani)mag 2.78
- Acamar (Theta¹ Eridani)mag 2.88
- Zaurak (Gamma Eridani)mag 2.97
- Rana (Delta Eridani)mag 3.52
- Beemim (Upsilon4 Eridani)mag 3.55
Can you see Eridanus from where you live?
This depends only on your latitude. Pick the row nearest to you; for your exact sky tonight, use the sky map.
| Latitude | Eridanus |
|---|---|
| 60°N | Only part of it ever clears the horizon |
| 40°N | Only part of it ever clears the horizon |
| 20°N | The whole constellation rises and sets |
| the equator | The whole constellation rises and sets |
| 20°S | The whole constellation rises and sets |
| 40°S | The whole constellation rises and sets |
| 60°S | The whole constellation rises and sets |
Questions about Eridanus
When is Eridanus best seen?
Eridanus stands highest in the sky at 9 pm local time in January. That makes winter evenings the best time for observers in the northern hemisphere; in the southern hemisphere the season is reversed.
What is the brightest star in Eridanus?
The brightest star in Eridanus is Achernar (Alpha Eridani), magnitude 0.45.
Where on Earth can you see Eridanus?
The whole of Eridanus can be seen from latitudes between about 90°S and 32°N. From 40°N: Only part of it ever clears the horizon. From 35°S: The whole constellation rises and sets.
What does Eridanus mean?
Eridanus is Latin for "the River". One of Ptolemy's 48 ancient constellations (2nd century).