And since Uranus takes half as long to orbit the Sun, it should also be in approximately the same place it was when Neptune was discovered.

But a Neptunian “month” would be based on Triton’s orbit! More math needed.

5.9 days, and BACKWARDS. I love Triton, the cantaloupe world. We really need to send a Cassini-style orbiter out there. We really need something more powerful than a radiothermal generator to power it, though.

The version I know is that Urbain Le Verrier of France and John Couch Adams of England, who were mathematicians and astronomers, independently predicted the location of the planet by measuring how the gravity of a hypothetical unseen object could affect Uranus’s path.

Le Verrier sent a note describing his predicted location of the new planet to the German astronomer Johann Gottfried Galle at the Berlin Observatory. Over the course of two nights in 1846, Galle found and identified Neptune as a planet, less than a degree from Le Verrier’s predicted position.

Gwif: “So when do we get to celebrate Pluto’s birthday?”
I don’t know. I’ll have to ask Mickey.

GDRFC = ??? [Puzzled & curious.]

To answer the original question as asked by (# 25.) Gwif : Pluto was discovered by Clyde Tombaugh in 1930 – Feb. 18th – and takes 248.09 years to complete one orbit. So rounding that figure up to 249 earth years [taps away on calculator] that would be about the year 2179.

EDIT : Ah, I see (#29.) MattF has given a similar answer too.

Messier Tidy Upper: spacecraft have not yet captured a “true” or “natural” image of Neptune. Voyager’s camera was only sensitive out to the orange end of the spectrum, and used orange filters in lieu of red. So it’s color is an approximation on those famous images like at the top of this fine article. Hubble shoots Neptune in near-infrared light where some cloud features become visible. In an eyepiece on a large telescope, the planet often appears dusky-blue to me; not very colorful, but blue nonetheless. Definitely not the vivid blue in the voyager photos.

Thanks I didn’t realise that. Must admit I always thought those were pretty much true colour, as we’d see them unaided eye images.

@ 21. Rebecca Harbison :

MTU:

Also, albedo is subjective when measured by our eyes ..[Snip] .. Neptune also gets less Sun than Uranus does, by virtue of it being further out, so there’s less to reflect — it doesn’t affect the actual albedo, but would affect a brightness measurement. (If a human were out at Neptune, though, his or her eyes would probably adapt.) Google tells me that Neptune’s albedo is about 0.4, which is comparable to Earth’s. Mercury’s is 0.14, so it would be much darker, if you could somehow place them side-by-side. Uranus’s is a bit more reflective (at 0.5), though.

&

@20. Doug :

@Messier Tidy Upper: Wikipedia has the albedo for the planets, both Bond albedo and Geometric .. [snip] .. Neptune and Uranus are somewhat similar, compared to other objects in the solar system. However, Neptune does have the lowest albedo of the gas giants. Mercury, Earth, and Mars have even lower albedo. But it also seems that Neptune’s albedo changes significantly with time.

My thanks go to both of you as well. Much appreciated.