Tecumseh's Eclipse and Astrophysics

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Introduction

When did the solar corona become recognized as actually being a part of the Sun, and who first called it by that name? The answers may be "1806" and "José José Joaquín de Ferrer y Cafranga," with kind of interesting historical wrinkles. See the excellent book "Totality", by Littman et al. (Ref. [1]) for the general background of eclipse science here. Ferrer made a great contribution to astrophysics by clearly describing what he saw - the corona - to be a part of the Sun, rather than of a lunar atmosphere or something else. In a sense this moment, a scant 200 years ago, was a major step towards astrophysics, as opposed to (say) positional astronomy; of course even now we debate the physics of the corona most assiduously. The Oxford English Dictionary (1971) wrongly attributes the term "corona" to Airy in 1851, whereas Ferrer's use of this term appeared in 1809 (Ref. [2]) .

Tecumseh's Eclipse and Old Kinderhook

This eclipse is associated with the name of the great Native American political and military figure Tecumseh and his brother, whose confederacy presented the last major obstacle for U.S. expansion into the "Old Northwest" east of the Mississippi. The Americans had obtained this region by international treaty, but unfortunately for orderly progress, the Native Americans who then lived there had not been invited to the treaty negotiations! Tecumseh's foreknowledge of the eclipse gained his cause some credibility.

Remarkably, the Ferrer observations of the eclipse were in Kinderhook, a small town in upstate New York, which was the birthplace of one of America's greatest presidents, Maarten (Martin) Van Buren. Among his accomplishments were the founding of the Democratic party and the avoidance of several potential wars. But he is most famous for having the nickname "Old Kinderhook" after his birthplace, conceivably leading to the American English word "okay" (OK). It is quite possible that Van Buren, who would have been 24 at the time of the eclipse, actually viewed the totality. In any case Figure 1 shows these three individuals, whose lives intersected in one way or another with the 1806 eclipse.

Figure 1: Images of three individuals involved in the 1806 eclipse: Tecumseh, José de Ferrer, and Maarten van Buren.

The 1806 eclipse science

Ferrer had excellent observing equipment, with sufficient angular resolution for him to recognize the rough structure of the lunar limb. He estimated that the lunar mountains were as large as "1 3/4 miles high". The physical inference that convinced him that this "corona" was in fact a part of the Sun was its great physical extent, as represented in his not very attractive sketch (Figure 2 here).

Figure 2: Ferrer's sketch of the corona of June 16, 1806. From this we might gather that he was not as good an illustrator as he was an astronomer!

Ferrer remarked that the Sun had no spots on that day. The year 1806 was late in a weak solar maximum and it may be surprising that the sketch shows such symmetry in spite of the spotlessness. Ferrer's main physical insight here was based on its large extent, though: via this he could directly exclude lunar or refractive explanations of its existence. Of course the problem of coronal heating - ie, the very existence of the corona - still has not been resolved, although we have some seriously more viable theories than Ferrer did.

References

[1] "Totality: Eclipses of the Sun," by M. Littmann, F. Espenak, and K. Wilcox (3rd Edition, Oxford University Press, 2009).

[2] "Observations of the eclipse of the Sun..." (Trans. Am. Philosophical Soc. 6, 264, 1809).