Did Galileo discover Neptune?

We all know that the farthest planet in the solar system, Neptune was discovered in 1846. French astronomer Johan Galle observed it first by using mathematical predictions in celestial mechanics done by French mathematician Urbain Le Verrier. As British mathematician, John Couch Adams also invented mathematical predictions there became a dispute over the credit of discovery. Ultimately the honor was shared.

History says that Johan Galle detected Neptune as the first time in the history of astronomy on September 23, 1846. But did you ever wonder whether any one might have at least seen it through a telescope before that day?

The answer is yes. But when and how? Neptune is even impossible to see in naked eye. Therefore even locating it in the night sky to focus a telescope is also impossible. So it must be accidental. Yes you thought right.

Our famous astronomer Galileo Galilei was very keen on observing Jupiter and its four moons discovered by him Also Jupiter was one of his favorite in the night sky. He observed a faint blue star very near to Jupiter at morning sky on December 28, 1612. Also he observed this faint blue star again just after a month at morning sky on January 27, 1613.  We know this because he took notes about these observations and it has been nearly two decades since the world have come to known about this.

Astronomers by calculations and computer simulations have found that this blue star is actually Neptune which was in conjunction with Jupiter at that time. Neptune was in a backward motion relative to earth as it had just turned retrograde motion in December 1612. It has been long speculated by astronomers that Galileo observed Neptune but he didn’t recognized it as a planet.

Do you want to see for yourself that how the sky looked like when he observed it? You don’t need to know any sort of mathematics. You just need the freeware Stellarium. Download and install it in your computer. Just set the location to Earth, Pisa and set the time to December 28, 1612. See the morning sky for yourself at about 7 AM. Bingo!! Here’s my view. I took some screenshots for you to see.

Do the same for January 27, 1613. Here are my screenshots.

In both cases you could see Neptune near Jupiter. COOL!! Isn’t it?

In July 2009 University of Melbourne physicist David Jamieson announced with evidence suggesting that Galileo was at least aware that the star he had observed had moved relative to the fixed stars.  He says that Galileo had marked the position of Neptune which he had observed on January 6 as a black dot on the notebook of his observation on January 28 1613.This black dot has been discovered as the precise position of Neptune on that day. Then he believes that as the object had moved relative to a star nearby Galileo might have thought that he had actually discovered a planet. Jamieson even decided to do a chemical analysis of the trace elements on the page of observation notes, intending to find whether he marked the January 6 observation on January 28.

So what do you think? I think that Galileo just missed his chance for being credited as the discoverer of planet Neptune.