COSMOS / CONSTELLATIONS / ERI
Eridanus (River)
The River. IAU abbreviation Eri. One of the 48 classical constellations listed by Ptolemy in the Almagest in the 2nd century AD.
STAR CHART
KEY FACTS
- IAU abbreviation
- Eri
- Latin name / genitive
- Eridanus / Eridani
- Position
- Right ascension ≈ 3 h 49 m; declination −57° to +0°
- Visibility from Türkiye
- From Türkiye only its northern part is seen, low on the southern horizon; the southern provinces are better placed.
- Best time to observe
- Best placed at 21:00 Türkiye time around 14 January.
- Number of stars
- 199 stars brighter than magnitude 6.5 in the catalogue; 47 brighter than 5 and 15 brighter than 4.
INTERACTIVE LAB
Where is Eridanus tonight?
Only the northern part of this constellation is seen from Türkiye, low on the southern horizon. The lab opens for Ankara on today’s date; switch the city to Antalya and then to Sydney and watch how the “Visible part” row and the chart change. The “Best night” button jumps to the best date (around 14 January).
MYTH, HISTORY AND OBSERVING
The mythical river into which Phaethon fell from the chariot of the Sun; it starts near Rigel at Orion’s foot and winds a very long way south. Bright Achernar at the river’s end is not visible from Türkiye. Epsilon Eridani, 10.5 light-years away, is one of the nearest stars known to host a planet.
BRIGHTEST STARS
| Star | Magnitude | Distance (light-years) | Spectral type |
|---|---|---|---|
| Achernar | 0.45 | 139 | B3Vp |
| Cursa | 2.78 | 89 | A3IIIvar |
| Acamar | 2.88 | 161 | A4III+ |
| Zaurak | 2.97 | 203 | M1IIIb |
| Rana | 3.52 | 29 | K0IV |
| υ⁴ Eri | 3.55 | 178 | B9V |
| φ Eri | 3.56 | 154 | B8IV-V |
| χ Eri | 3.69 | 58 | G5IV |
Magnitude: apparent brightness; the smaller the number, the brighter the star. Distances derive from parallax measurements and are uncertain for distant stars. Source: HYG v4.1 star catalogue (CC BY-SA 4.0).
SOURCES
Position, visibility and best observing time were computed approximately for this page from the catalogue stars (Ankara, 39.9° N). The 88 constellations were adopted by the IAU in 1922; their boundaries were drawn by Eugène Delporte in 1930.