Galileo was the first to see Neptune, making a note of it in 1613 — but because it appeared nearly stationary in the sky, he didn’t recognize it as a planet. It would be another 233 years before Johann Gottleib Galle rediscovered Neptune, directed by calculations made by Urbain Le Verrier, who had observed irregularities in Uranus’ orbit that could best be accounted for by the existence of another, undiscovered body beyond that planet’s orbit. Galle’s discovery of Neptune in 1846 — less than a degree from the position suggested by Le Verrier’s calculations — would have a profound influence on the search for Planet X some decades later.
The great strangeness of the discovery of Pluto is this: Percival Lowell’s calculations of the irregularities in Uranus’ orbit suggested that a roughly Neptune-sized planet remained to be discovered at the edge of the solar system, beyond Neptune itself (a “Trans-Neptunian Object”). And in 1930, Pluto was indeed discovered very close to the position Lowell predicted for it.
But Pluto is far too small to have introduced any significant wobble into any object’s orbit. So why did Lowell’s math send him right to Pluto’s position?
As it turns out, Pluto’s location was nothing but an amazing, impossible coincidence. Still, it’s hard not to imagine some kind of mystical explanation, as though Lowell had managed to divine some truth about the Solar System simply by sitting in the high desert air for decades.
And as it happens, there aren’t any significant wobbles in Uranus’ orbit; the observations Lowell was using were minutely faulty.
Well, it is a mystery.
April 4, 2010 at 8:21 am
[…] How terrible if Lowell had spent all those years just chasing ghosts. […]
May 1, 2010 at 8:53 pm
[…] As I’ve written here before, the astronomers at Lowell weren’t sure what they had. The object was too small to be the gas giant they’d been expecting. But their mathematics seemed to indicate that a gas giant was indeed what was out there to discover; only a very large planet could perturb the orbits of Uranus and Neptune in the way that was posited. So they were understandably puzzled to have found a very small object in just the place that Lowell’s mathematics suggested a gas giant would be. […]
May 18, 2010 at 8:45 am
[…] is emphasized — though in fact the discovery of Pluto in the location Lowell predicted was nothing more than an astounding coincidence. Possibly related posts: (automatically generated)The smoldering gun.Calling all loonies.The […]
May 21, 2010 at 11:09 am
[…] has to strike us as almost theatrically staged, tinged with madness, loss and obsession — and aligned in some mysterious fashion with the hidden workings of the […]