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Did Galileo let Neptune slip through his fingers?

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Galileo Galilei – there’s no stopping him. Not content with chucking things off the top of the leaning tower of Pisa, or making nifty telescopes to stare at the stars with, it is now being mooted that ol’ GG discovered Neptune, some 200 years or so before it was officially discovered.

Its widely accepted that in 1612 and again in 1613 Galileo must have observed Neptune, although at the time he thought it was a star, spotted during his observation of Jupiter’s moons. But physicist David Jamieson from the University of Melbourne, Australia, says that history has judged Galileo incorrectly – and that his notebooks reveal that he knew he was looking at a planet after all.

Jamieson noticed that on January 28 1613 Galileo makes note of a “star” that seemed to have moved in relation to its nearest starry neighbour – behaviour only seen by planets when observed from Earth. An earlier entry, from January 6 1613 also has an unlabelled black dot in the position now recognised to be where Neptune sits.

Jamieson thinks this dot was added later, possibly on January 28th. “I believe this dot could reveal he went back in his notes to record where he saw Neptune earlier when it was even closer to Jupiter but had not previously attracted his attention because of its unremarkable star-like appearance," he says (press release).

How will we ever know for sure? There’s a chance that trace element analysis could tell the difference between when different inks were used. Or maybe, Jamieson suggests, somewhere in one of Galileo’s letters or notes he wrote one of his famous coded messages or anagrams claiming he’d discovered the planet, and this note is just waiting to be discovered.

Even better as a conspiracy theory (my own special theory) – maybe this note, if such a thing exists, was actually discovered by the astronomers who claimed Neptune for themselves in 1846; Johann Gottfried Galle, working at the Berlin observatory on predictions made by Urbain Le Verrier. Then, while revelling in their own glory, maybe they destroyed Galileo’s encrypted message.

The plot thickens…

Image: NASA

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