Portal:Astronomy/Did you know/6


 * ... that the asteroid 2011 XC2 missed the Earth by less than 1 lunar distance on 3 December 2011?
 * ... that the mass-luminosity relation, first derived by Arthur Eddington in 1924, helps astronomers find the distances to binary star systems?
 * ... that the planetary nebula Abell 39 is unusually spherical, yet its central star is offset from the center?
 * ... that data from Mariner 10 led to the discovery of Mercury's magnetic field in 1974?
 * ... that the Toronto Magnetic Observatory had to be moved as the University of Toronto's electric lighting was interfering with observations?