Happy Birthday, Neptune

On July 12th 2011, Neptune is one year old - one Neptunian year that is. The furthest planet from the sun it's only now completed one solar orbit since its discovery in 1846, travelling so slowly each Neptunian season lasts forty Earth years.

Too distant to spot with the naked eye the ancients could never have known of Neptune's existence. Nineteenth century astronomers had to climb on the shoulders of scientific giants to see it. First a tiny blue disc now an ice giant whose strange atmospheric features send shivers down the spines of astronomers today.

What twists and turns of fate, what scientific clues and personality clashes won the race for Neptune's discovery? Some say Galileo spotted it 200 years earlier, secretly noting its existence in a coded Latin anagram awaiting further proof. What secret phrase might be lurking in his notebooks awaiting discovery by 21st century scientific spoofs?

It's late spring, early summer in Neptune today. It's been that way for decades. Astronomers can only watch and marvel at the weather on Neptune and the jazzy, jerky dance of its Great Dark Spot - first in the southern hemisphere, then in the north, sometimes gone altogether. What is it? Where does it come from? What can you ever know about a world when even the most advanced human telescopes have only studied it for a season?

Written and presented by Tracey Logan.