Mikhail Lomonosov
Astronomy

Lomonosov was the first to discover and appreciate the atmosphere of Venus during his observation of the transit of Venus of 1761 in a small observatory near his house in St Petersburg. At least in the English-speaking world, this attribution seems to have been owing to comments from the multi-lingual popular astronomy writer Willy Ley (1966), who consulted sources in both Russian and German, and wrote that Lomonosov observed a luminous ring (this was Ley's interpretation and was not indicated in quotes) and inferred from it the existence of an atmosphere "maybe greater than that of the Earth" (which was in quotes). Because many modern transit observers have also seen a threadlike arc produced by refraction of sunlight in the atmosphere of Venus when the planet has progressed off the limb of the Sun, it has generally, if rather uncritically, been assumed that this was the same thing that Lomonosov saw. Indeed, the term "Lomonosov’s arc" has frequently been used in the literature.

In 2012, Pasachoff and Sheehan consulted original sources, and questioned the basis for the claim that Lomonosov observed the thin arc produced by the atmosphere of Venus. A reference to the paper was even picked up by the Russian state-controlled media group RIA Novosti on 31 January 2013, under the headline "Astronomical Battle in US Over Lomonosov’s discovery." An attempt was made by a group of researchers to experimentally reconstruct Lomonosov's observation using antique telescopes during the transit of Venus on 5–6 June 2012. One of them, Y. Petrunin, suggested that the telescope Lomonosov actually used was probably a 50 mm Dollond with a magnifying power of 40x.

It was preserved at Pulkova Observatory but destroyed when the Germans bombed the observatory during World War II. Thus, Lomonosov's actual telescope was not available, but other presumably similar instruments were employed on this occasion, and led the researchers to affirm their belief that Lomonosov's telescope would have been adequate to the task of detecting the arc. Thus A. Koukarine, using a 67 mm Dollond on Mt. Hamilton, where seeing was likely much better than Lomonosov enjoyed at St. Petersburg, clearly observed the spiderweb-thin arc known to be due to refraction in the atmosphere of Venus. However, Koukarine's sketches do not really resemble the diagram published by Lomonosov.

Koukarine's colleague V. Shiltsev, who more nearly observed under the same conditions as Lomonosov, using a 40 mm Dollond at Batavia, Illinois, produced a close duplicate of Lomonosov's diagram. However, the rather large wing of light shown next to the black disk of Venus in his drawing (and Lomonosov's) is too coarse to have been the arc. Instead it appears to be a complicated manifestation of the celebrated optical effect known as the " black drop ". It should be kept in mind that, as stated in Sheehan and Westfall, "optical distortions at the interface between Venus and the Sun during transits are impressively large, and any inferences from them are fraught with peril".

Again, the actual words used by Lomonosov do not refer to an "arc" at all. In the Russian version, he described a brief brightening lasting a second or so, just before third contact, which appeared to Pasachoff and Sheehan to most probably indicate a last fleeting glimpse of the photosphere. As a check against this, Lomonosov's German version (he had learned to speak and write German fluently as a student at Marburg) was also consulted; he describes seeing "ein ganz helles Licht, wie ein Haar breit"=”a very bright light, as wide as a hair". Here, the adverb "ganz" in connection with "helles" (bright) could mean "as bright as possible" or "completely bright"), i.e., as bright as the surface brightness of the solar disk, which is even stronger evidence that this can't be Venus's atmosphere, which always appears much fainter.

Lomonosov's original sketches, if they existed, do not appear to have survived, Modern observations made during the nineteenth century transits and especially those of 2004 and 2012 suggest that what Lomonosov saw was not the arc associated with the atmosphere of Venus at all but the bright flash of the solar photosphere before third contact. The first observers to record the actual arc associated with the atmosphere of Venus, in a form comporting with modern observations, appear to have been Chappe, Rittenhouse, Wayles and Dymond, and several others at the transit in June 1769.

In 1762, Lomonosov presented an improved design of a reflecting telescope to the Russian Academy of Sciences forum. His telescope had its primary mirror adjusted at an angle of four degrees to the telescope's axis. This made the image focus at the side of the telescope tube, where the observer could view the image with an eyepiece without blocking the image. This invention was not published until 1827, so this type of telescope has become associated with a similar design by William Herschel, the Herschelian telescope.
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