1 8 – 1 8 2 0 . ▁He ▁had , ▁however , ▁long ▁been ▁a ▁student ▁of ▁science ; ▁and ▁Dr ▁Dir cks , ▁a ▁phys ician ▁pract ising ▁at ▁T ø nder , ▁pre va iled ▁with ▁his ▁father ▁to ▁send ▁him ▁in ▁ 1 8 2 0 ▁to ▁C open hagen , ▁where ▁he ▁won ▁the ▁patron age ▁of ▁H . C . ▁Sch um acher ▁and ▁attract ed ▁the ▁personal ▁notice ▁of ▁King ▁Frederick ▁VI . ▁The ▁Dan ish ▁survey ▁was ▁then ▁in ▁progress , ▁and ▁he ▁acted ▁as ▁Sch um acher ' s ▁assistant ▁in ▁work ▁connected ▁with ▁it , ▁chief ly ▁at ▁the ▁new ▁observ atory ▁of ▁Al ton a , ▁from ▁ 1 8 2 1 – 1 8 2 5 . ▁ ▁Th ence ▁he ▁passed ▁on ▁to ▁Goth a ▁as ▁director ▁of ▁the ▁See berg ▁observ atory ; ▁nor ▁could ▁he ▁be ▁tempt ed ▁to ▁rel in qu ish ▁the ▁post ▁by ▁success ive ▁inv itations ▁to ▁replace ▁F . G . W . ▁Str uve ▁at ▁Dor pat ▁in ▁ 1 8 2 9 , ▁Friedrich ▁Wilhelm ▁August ▁Ar gel ander ▁at ▁Hels ink i ▁in ▁ 1 8 3 7 , ▁and ▁F . W . ▁B essel ▁at ▁König s berg ▁in ▁ 1 8 4 7 . ▁The ▁problems ▁of ▁gravit ational ▁astronom y ▁engaged ▁the ▁chief ▁part ▁of ▁Hans en ' s ▁attention . ▁A ▁research ▁into ▁the ▁mut ual ▁perturb ations ▁of ▁Jup iter ▁and ▁Sat urn ▁secured