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Also known as Jordanus Fluvius, a constellation representing the river Jordan, introduced by the Dutchman Petrus Plancius on his celestial globe of 1612. Jordanus rose under the tail of the Great Bear in what is now the constellation of Canes Venatici. The German astronomer Jacob Bartsch explained in his Usus Astronomicus Planisphaerii Stellati of 1624 that the river had two sources, namely Jor and Dan, but not every map showed it this way. One that did was by Bartsch’s mentor Isaac Habrecht II in 1628 (see below); Habrecht had previously included Jordanus and other new Plancius constellations on a globe of 1621 from which Bartsch first learned of them. Despite his description, Bartsch’s own star charts depicted Jordanus starting at a single source, the star we now know as Cor Caroli in Canes Venatici.
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Jordanus flowing beneath the feet of Ursa Major as shown by Isaac Habrecht II on a planisphere in his book Planiglobium coeleste ac terrestre (1628). The bright star at the confluence of the twin headwaters is the one we now know as Cor Caroli in Canes Venatici. (Image courtesy ECHO, Berlin.)


From the tail of Ursa Major Jordanus flowed between the Bear and Leo (an area now occupied by Hevelius’s subsequent creations Leo Minor and Lynx) and ended near the head of the Bear next to Camelopardalis, another Plancius invention. The German globe maker Johann Ludwig Andreae reversed the direction of flow on his planisphere of 1724, placing the twin sources next to the head of the Bear.

Jordanus became largely forgotten during the 18th century once Hevelius had introduced Canes Venatici, Leo Minor and Lynx in this same area, and it was not shown by Bode.



© Ian Ridpath. All rights reserved


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