Historical homework: Where was Uranus at discovery?

[Blue Skies]

I'm writing up an article for the local society on Gemini and was going to include a well-worn paragraph about how Uranus was in Gemini at discovery. But where in Gemini? Pluto was near delta Geminorum when discovered, but no one ever really says where Uranus was. So I decided I should dig around a bit further ...and found out that in the sky as we know it today it was Taurus at the time.

Before you run off on speculation, consider the following: Depending on what Epoch and dating system you use, Uranus was either at 5h 36m RA or 5h 49m RA (on 13 March 1781). Both positions are well within the modern day boundaries of Taurus, not far from the Crab Nebula, M1. I find most people forget that the constellations we use today were agreed upon in 1930 and before that time constellation boundaries tended to be a bit loose and open to interpretation. To confuse things (and don't kill me here) in astrological terms Uranus was at 24 deg 27 min of Gemini. Could this be where the confusion comes from? Or were the boundaries of Gemini in Herschel's day far different to our own? Anyone with better historical knowledge about this? The internet is letting me down on it at the moment.

[ballaratdragons]

Hi Jacquie,

I don't know how much information you have collected, but this may be of some interest to you.

It is Herschels hand written notes about his 'discovery' of a comet-looking object (previously mistaken as a star), which was Uranus. He explains Uranus' location in the FOV of his scope.
First, at the top of his notes he dates it March 12 at 5:40 am and reports his observations of Mars and Saturn.

Now for the exciting bit!
Then below that, dated Tuesday March 13 when looking around the Pollux area he writes:
"Pollux is followed by 3 small stars about 2' and 3' distance.
(?) as usual, p h
in the quartile near ζ Tauri (Zeta Taurus) the lowest of the two is a curious other Nebulous star or perhaps a Comet.

Then he strikes out the following:
preceeding the star that preceeds ν Geminorium (Nu Gem) ? about 30"

then continues in his note: a small star follows the Comet at 2/3 of the field's distance

Now, without knowing the FOV he was using it makes it hard to determine his distance of '2/3 of the field's distance'. I also do not know the quality of his optics.
I get from his notes that he sees 3 small stars only 2 - 3 minutes of arc from Pollux in the direction of ζ Tauri, but then he says "in the quartile near ζ Tauri!" He also says Pollux is 'followed by' the 3 stars. That would put them on the opposite side of Pollux away from ζ Tauri.

In my thoughts of his notes I 'think' he saw Uranus near ζ Tauri (in the quartile of ζ Tauri). His notes say he saw it near ζ Tauri, and Cartes du Ciel tells us that Uranus was between ζ Tauri and M35 on the 13th March 1781, so how he can say the 3 stars 2' - 3' from Pollux is beyond my understanding.

But we can work out for sure that he saw it right near ζ Tauri :thumbsup:
I hope all this helps. My Brain now hurts trying to work it all out to this point. :P

Here are his actual hand written Notes:http://www.sciencephoto.com/image/364195/530wm/V7000161-Discovery_of_Uranus_by_Herschel,_17 81-SPL.jpg
Photo Credit: Royal Astronomical Society/Science Photo Library

.

[Blue Skies]

Thanks for that find, Ken. Looking at the notes, I would say that the observation about Pollux was separate from the one about zeta Tauri. That seems to clear it up, though. I might try and work out where I got the Gemini reference from, now - and not mention that it was in Gemini at the time again!

[ballaratdragons]

Ahhh yes, good observation Jacquie.

That would explain the line he drew between "as usual. p H" and "in the quartile near ζ Tauri".

They were different observations on the same night. I would say he was looking in the Pollux area, drew a line to end his report of that observation, then started his next observation "in the quartile near ζ Tauri".

Sounds fair to me :)

The 'Gemini' reference you read somewhere might be connected to his writings because he mentioned Pollux in his report :shrug:

[glenc]

Jacquie
Attached is a SkyMapPro map showing Uranus the day it was discovered from Bath. The map is for 7pm on 13 March 1781 from London.
Uranus was 7d 50m from mu Gem then. It moves very slowly across the sky. On 23 June 1781 it was near M35.
It was in Taurus on 13/3/1781 using today's constellations.
Glen

[overlord]

I will only refer to that overblown asteroid as Georgium Sidus III. I am an arch conservative and distastefully decline to condescend towards continental aspirations, with the exception of my marmelade breakfast, served on the finest trencher.

[glenc]

The planet should be called Herschel not U.