127 Johanna [SEP] named after
127 Johanna
Johanna (minor planet designation: 127 Johanna) is a large, dark main-belt asteroid that was discovered by French astronomers Paul Henry and Prosper Henry on 5 November 1872, and is believed to be named after Joan of Arc. It is classified as a CX-type asteroid, indicating the spectrum shows properties of both a carbonaceous C-type asteroid and a metallic X-type asteroid.
A photoelectric study was performed of this minor planet in 1991 at the Konkoly Observatory in Hungary. The resulting
after Marin Mersenne, because 8191 is a Mersenne prime (3 Juno, 7 Iris, 31 Euphrosyne and 127 Johanna having been discovered and named during the 19th century).
In geometry, an integer right triangle that is primitive and has its even leg a power of 2 (  ) generates a unique right triangle such that its inradius is always a Mersenne number. For example, if the even leg is then because it is primitive it constrains the odd leg to be , the hypotenuse to be and its inradius to