Christmas Comet 46P/Wirtanen Estes Park Memorial Observatory Posted on December 22, 2018 by Estes Park Memorial ObservatoryDecember 22, 2018 On Dec. 16, Comet 46P/Wirtanen made its closest approach to Earth in more than 20 years. On Dec. 16, Comet 46P/Wirtanen made its closest approach to Earth in more than 20 years,