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ERIDANUS
The River
Eridanus - Uranometria by Johann Bayer - 1661
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The river Eridanus begins humbly (as all rivers do), at the feet of Orion. Meandering toward the west, it loops back on itself, and soon dips south, becoming lost from view to most northern hemisphere observers. Those below 32 degrees north latitude see the river Eridanus winding and tumbling down amongst the southern constellations to end with a splash at the bright star Achernar, almost level with the second brightest star in the night sky, Canopus.
The brightest star in the constellation Eridanus (Alpha Eridani) is named Achernar, from the Arabic for the star at the end of the river. Even though it is 120 light years away, it is the ninth brightest star in the sky, a B5 blue giant, seven times the diameter of our Sun, and twice as hot. It has an apparent magnitude of 0.46.
The second brightest star (Beta Eradani) is named Cursa, Arabic for footstool. Along with three other stars it forms a square asterism known as the footstool of Orion. In ancient times the square of stars was also known as the ostrich nest.
The next brightest star is Zaurak, Arabic for boat. It has a magnitude of 2.98.
Theta Eridani was given the name Acamar, taken from Achernar, because for a time this was where the original constellation ended.
53 Eridani is named Sceptum, because at one time it was the brightest star in a small constellation called The Sceptre Of Brandenburg, just below the first bend in the river. It was eventually dropped as an official constellation.
NGC 1300 is a barred spiral galaxy with a magnitude of 11.4, 69 million light years away.
NGC 1232 is a large spiral galaxy with a magnitude of 10.9, 60 million light years away.
Hiding inside the Footstool of Orion, too faint to see without long exposure photographs, IC 2118, or The Witch Head Nebula, really does look like a profile of the proverbial wicked witch.
Eridanus contains six stars that host planetary systems, and one of them, Epsilon Eridani, is easily visible with the naked eye, with a magnitude of 3.73. Finding planets around this star is especially significant because it is so close to us. At a distance of only 10.4 light years, it is the third closest visible star, second only to Proxima Centauri, and Sirius. For more information go to http://en.wikipedia.org/wiki/Epsilon_Eridani.
Eridanus also contains the star purported to host the planet Vulcan, fabled home of Star Trek's Mr. Spock. The creator of Star Trek, Gene Roddenberry, chose the star 40 Eridani for this distinction because of its close proximity (only 16.5 light years away), and other characteristics that were similar to the fictional Vulcan sun. With a magnitude of 4.43, it is faint, but visible.
For more information, go to NASA's Planet Quest.
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