Eridanus

The River

A long, winding river of faint stars that starts near Rigel in Orion and flows south, mostly below the horizon for northern observers.

Chart drawn as the sky looks when you face the constellation: north is up and east is to the left. Dot size shows brightness, and color hints at temperature. The connecting lines are one common stick figure; other traditions draw them differently.

Best season: Winter
Best months: December through February, low in the south on winter evenings
Visibility: Visible from the United States, but its southern end, including the bright star Achernar, stays below the horizon for most of the country
Abbreviation: Eri

How to find it

Start at Rigel in Orion and find Cursa, a modestly bright star just to the upper right.
From there, the river winds west and south through faint stars.

Brightest stars

Cursa (just beside Rigel)
Achernar (the river's end, not visible from most of the US)

What to look for

The first stretch of the river, near Orion, is the easiest part to see from the United States.

Binocular and telescope targets

Epsilon Eridani: a nearby star only about ten light-years away, visible to the naked eye

Using it to find other things

Eridanus begins near Rigel and winds south toward the southern sky.

About this constellation

Eridanus is one of the largest constellations, but most of it is faint and low. From the northern United States, only the opening bends of the river near Orion are easy to trace.

Achernar, the brightest star in the river, is far to the south and never rises for most American observers.

Related guides

Visibility depends on your latitude, the date, and the time of night. The months above assume a typical evening from the contiguous United States, so use a planetarium app to confirm what is up tonight. Never look at the Sun through binoculars or a telescope without a proper solar filter.

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