8 December

Hansen was a Danish astronomer whose most important work was the improvement of the theories and tables of the orbits of the principal bodies in the Solar System.

The work in celestial mechanics for which he is best known are his theories of motion for comets, minor planets, moons and his lunar tables, published in 1857. He published his lunar theory in Fundamenta ('Foundation') in 1838, and Darlegung ('Explanation') in 1862-64.