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Sky Tonight—January 23, Eridanus-a winding river of stars

Courtesy of EarthSky
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Bright star in southwest on January evenings? It’s the planet Jupiter

Here is a constellation for you if you have access to a very dark sky: Eridanus the River. You will not see this one from the city, or even the suburbs. Eridanus the River begins near the star Rigel in the constellation Orion the Hunter – and wells up in a great loop before ambling back down toward the southern horizon.

Rigel: Orion’s brightest star

Eridanus is one of the longest and faintest constellations. It has variously said to represent the Nile, Euphrates, or the River Po. It has also sometimes called the River of Orion or River of Ocean. In Homer’s day in ancient Greece, it was thought that the River of Ocean encircled a flat Earth.

Why search for such a faint constellation? Only because it is very beautiful. And seeing Eridanus – understanding its association with a river in the minds of the early stargazers – can give you a kinship with those stargazers from centuries ago.

Bright object in the southeast before sunrise? It’s the planet Venus

From most of the U.S., the River disappears below the southern horizon. However, if you live at a very southerly latitude in the U.S., you can see a special sight: the star that represents the end of the River. This star is Achernar.

Star Achernar marks the end of the River

Can you find this long, meandering river of stars called Eridanus in your sky?

Written by EarthSky

Astronomy Picture of the Day from NASA/JPL

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Universe Today

StarDate Online

Sky and Telescope

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Simostronomy Blog

Amazing Space

The York County Astronomical Society

Scope City

James S McDonnell Planetarium

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