29-04-2011

Fortin - Other weird findings

The truth about the identity of M109
When Uranus still was a star
M47, M48, M50
48 Herculis - a variable star?
Novae and a variable star
The Supernova of Tycho, 1572
The Supernova of Kepler, 1604

The truth about the identity of M109
Key message: NGC 3992 isn't M109, NGC 3953 is M109.

Since 1953 (after research by and publication of Owen Gingerich in Sky & Telescope) it is generally accepted that NGC 3992 has to be identified as M109. I don't think so. My opinion is that NGC 3953 is actually M109. Proof can be found in the Fortin 1795 atlas which was edited by Joseph Jérome le Français de Lalande & Pierre Méchain. The last person is really important here, because he was actually the discoverer of the nebula that was later named M109 (after Messier) and was misidentified with NGC 3992. Misidentified indeed, because on plate 6 (above left) (and also on plate 7) of the 1795-atlas a nebula is drawn exactly on the position of NGC 3953. Here the discoverer himself makes a clear statement: he has discovered NGC 3953 and not NGC 3992.

More proof is submitted by the fact that although both are almost of the same brightness, because of the fact that NGC 3953 is smaller than NGC 3992, the total brightness is spread over a smaller area, which leads to a higher surface brightness, and makes it an easier target in small telescopes.

There is another scenario possible:
Mechain made his discovery on March 12, 1781. Messier observed it on March 24, 1781. But did he actually? Maybe Messier did observe (and as a matter of fact discover) NGC 3992, but mixed it up with Méchains observation twelve nights earlier. On October 21st 2006 (and again on December 4th) I wrote an email to Prof. Gingerich to try to clarify this.
Unfortunately I still have not received a reaction from him, but he is a busy scientist, so it might have slipped his attention. So I send another email on May 26th 2007.  Also no reaction. I'll just leave it like that.

In the Dutch astronomy-magazine 'Zenit' of February 2007 and the French 'Astronomie Magazine' of July/August 2007 an article was dedicated to this reconsideration of the true identity of M109.

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When Uranus still was a star

This can be found on Plate 14.
In the Atlas Céleste the planet Uranus is drawn as a tiny star in Taurus, the Bull. Uranus was 'discovered' by William Herschel on March 13 1781 near  η Gem (η of the Twins), he reported it as a comet on April 26 to the Royal Astronomical Society. In 1782 Lexell and La Place recognised that the new discovery was not a comet but a planet. On November 7 1782 Herschel called the new planet 'Georgium Sidus' to honour king George III, who gave him a house and a £ 200 per year salary.  Lalande proposed the name 'Herschel' in 1792, but it was Bode whose proposal 'Uranus' made it finally after Herschel's death in 1822.

In the 1776 edition, Uranus is just shown as a tiny star; in the 1795 edition the planet is called 'Herschel' in honour of it's discoverer. 

This tiny star was first seen by John Flamsteed in 1690 on December 13. Flamsteed however failed to recognise it being not a star. He added Uranus as the star '34 Tau' (34 of the Bull) in his 'Catalogus Brittanicus' of 1725. That's how the star got into several atlases  between 1729 and 1830 (e.g. Flamsteed, Bevis, Fortin, Bode, Reissig, Jamieson). Astrohistorians figured out that observations of Uranus had been recorded 19 times before Herschel spotted it in 1781, not only by Flamsteed, but also by Bradley, Meyer and Le Monnier.
Tobias Mayer's sighting of Uranus in 1756 made it into the 1805 edition of Bode's 'Vorstellung der Gestirne', where it can be found on plate 21 near Aquarius, the Water Bearer.
In the 1782 edition Uranus can also be found, albeit as a star. In both the Fortin' editions this star is not drawn. Uranus' position is in agreement with its calculated position in the Fall of 1756.
(Software used for this calculation: TheSky, version 5.)

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M47, M48, M50

This can be found on Plate 25 of the 2B and 3 edition..
The story of Messier regarding M47 and M48 is a nice one.
And there is also something peculiar with M50 and its neighbouring stars.

Giangi Caglieris brought the M48 case to my attention. Messier made a mistake when positioning it. It was later (re)discovered by Bode, who however didn't realise he had seen M48 on its correct position. This is why M48 is drawn twice in his 1782-atlas and also in the 1795 edition of Fortin (which can be seen below) and also in Bode's atlas of 1805.

M47 was also positioned wrong by Messier.

M50 is a completely different story. The position (declination and right ascension) itself is OK, but the surrounding stars are drawn far more north than they should. In fact, where there are two stars drawn next to M50, there actually should have been drawn three stars. One on the exact location of M50!
So to say: the correct position of M50 is in fact the wrong position of a third star from a group where only two are drawn (both at the wrong position).

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48 Herculis, a variable star?

This can be found on Plate 8.
In the Atlas Céleste of 1795, only a few variable stars are named 'variable' or 'changeante':
Mira, Chi Cygni (see below) ánd 48 Her.
The last one is really a mistake: 48 Her is not a variable star.
However in the preface of the 1795 edition there is a list, which refers to Lalande, of several star that are possible variable. When looking at the individual plates, only 48 Her was designated as 'changeante'. Why so, I really don't know.

Notice that Lalande is called 'citoyen', meaning 'citizen'. This is because the 1795 edition was published áfter the French Revolution, that started in 1789.
Lalande (ánd the copperplates of the 1776 edition) apparently survived!

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Novae and a variable star

This can be found on Plate 11.

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The Supernova of Tycho, 1572

This can be found on Plate 2.

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The Supernova of Kepler, 1604

This can be found on Plate 9 of both the 1776 edition 2B and the 1795 edition.
Beside the supernova, also M9 and M23 are shown.

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