This Space.com story was on the Flamsteed Facebook page the other day and I thought it was absolutely fascinating. Compelling (if not conclusive) evidence that Galileo not only ‘saw’ Neptune, but that he realised he wasn’t looking at just another star but a planet.
Now the question is, has one of his famous ‘discovery anagrams’ long since gone missing?
That was a fascinating article… not entirely convinced that Galileo thought it was a planet, but there is some interesting evidence there.
This has reminded me that Neptune was almost discovered on several occasions before its eventual discovery in 1846. John Herschel nearly discovered the planet on 14 July 1830, as he informed Le Verrier in a letter written on 9 January 1847. He recognised the object he observed was not a star because it showed a small disk, but he supposed it to be a planetary nebula and thought no more of it.
Michel Lefrançois de Lalande, the nephew of Joseph Jérome de Lalande, observed Neptune on 6 and 8 May 1795 with the transit instrument of the observatory at the École militaire. He recorded it as a star whose positions differed slightly between two observations. However, believing this to be an observational error, his uncle Jérome de Lalande only gave the second position, that of 8 May, in his Histoire céleste .
Le Verrier – Magnificent and Detestable Astronomer. Lequeux, J. 2013.