The end of the celestial river really isn’t the end of the river. That’s because the river has two stars with almost the same name — and both names mean “the end of the river.”

Eridanus is in the south and southeast as night falls. It begins near Rigel, the bright star at the foot of Orion. It then makes as many twists and turns as most earthly rivers before reaching its first “end,” Acamar. After that, it keeps going until it reaches the final end, Achernar. From the United States, you have to be in Hawaii or far southern Texas or Florida to see that second ending.

In fact, that’s exactly why Eridanus has two endpoints. From the latitudes of ancient Greece, where the constellation was drawn, skywatchers could see only down to Acamar — everything else remained below the horizon. So Eridanus ended right there.

Centuries later, though, European ships cruised into the southern hemisphere. Crew members saw a much brighter star down to the lower right of Acamar, so they added it to the outline of Eridanus. And they gave it a nearly identical name — giving the river a brighter end.

Acamar is far to the lower right of Orion. It’s only third magnitude — a fairly faint star that’s hard to find without a chart. Achernar is several times brighter, so it’s hard to miss — but only if you’re south of about San Antonio or Daytona Beach. It stands due south, just a skosh above the horizon, a couple of hours after sunset.
 

Script by Damond Benningfield

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