Question

The trans-neptunian object sedna has an extremely large semimajor axis. in the year 2004, it was estimated to be 480 au. what is the period of sedna's orbit, measured in earth years?

Answer 1

The orbital period is proportional to the 3/2 power of the semi-major axis. Earth, with a semi-major axis of 1 au has a period of 1 year, so Sedna is expected to have an orbital period of
  480^(3/2)×(1 year) ≈ 10,516 years