40 Eridani

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40 Eridani is a triple star system in the constellation of Eridanus, abbreviated 40 Eri. It has the Bayer designation Omicron2 Eridani, which is Latinized from ο2 Eridani and abbreviated Omicron2 Eri or ο2 Eri. Based on parallax measurements taken by the Gaia mission, it is about 16.3 light-years (5.0 parsecs) from the Sun. The primary star of the system, designated 40 Eridani A and formally named Keid, is easily visible to the naked eye, with an apparent magnitude of 4.43. It is orbited by a binary pair whose two components are designated 40 Eridani B and C, and which were discovered on January 31, 1783, by William Herschel. It was again observed by Friedrich Struve in 1825 and by Otto Struve in 1851. In 1910, it was discovered that although 40 Eridani B was a faint star, it was white in color. This meant that it had to be a small star; in fact it was a white dwarf, the first discovered. Although it is neither the closest white dwarf, nor the brightest in the night sky, it is by far the...

Read on Wikipedia · Image Eridanus_constellation_map.png: Torsten Bronger derivative work: Kxx (talk), CC BY-SA 3.0