The planet Neptune is seen here in the constellation Aquarius Monday September 21, 2015. Neptune has completed one orbit of the sun and has returned to the constellation where it was first viewed 169 years ago. The bright star at top left is Lambda Aquarii also known as Hydor. (Michael E. Palmer/Palmer's Almanac)
Urbain Le Verrier did the math and his figures were correct. He had discovered a planet. Without looking through a telescope Verrier had discovered what the human eye couldn’t- our solar systems 8th planet, Neptune. Years earlier William Herschel had discovered Uranus with his homemade telescope. Uranus displayed an irregular orbit and caused some to believe an unknown planet lay beyond the 7th planet’s orbit. The unknown planet was verified to exist when Johann Galle viewed it through his telescope on September 23, 1846. Galle spotted the planet one degree from where Verrier had predicted the planet would be in the constellation Aquarius. Verrier named his planet for the Roman god of the sea. It takes Neptune 164 earth-years to make one orbit around the sun. So if you look for Neptune in the night sky you’ll find it right back where Galle saw it 169 years ago just down and to the right from the star Lambda Aquarii. At 2,907 million miles from earth Neptune is just too faint to see with the unaided eye. You’ll need a pair of binoculars, a telescope or a long camera lens to see the planet discovered through mathematical reasoning.
Michael E. Palmer is a writer and photographer based in Alabama.
He can be reached at firstname.lastname@example.org