Sunspot Observations During the Maunder Minimum from the Correspondence of John Flamsteed

Abstract

We compile and analyze the sunspot observations made by John Flamsteed for the period 1672 – 1703, which corresponds to the second part of the Maunder Minimum. They appear in the correspondence of the famous astronomer. We include in an appendix the original texts of the sunspot records kept by Flamsteed. We compute an estimate of the level of solar activity using these records, and compare the results with the latest reconstructions of solar activity during the Maunder Minimum, obtaining values characteristic of a grand solar minimum. Finally, we discuss a phenomenon observed and described by Stephen Gray in 1705 that has been interpreted as a white-light flare.

Appendix: Sunspot Observations Made by John Flamsteed Recovered from his Correspondence

We present here the transcriptions of the relevant texts on sunspot observations by Flamsteed. We also indicate the number of the letter that is assigned in the compilation by Forbes, Murdin, and Wilmoth (1997) and the date of the letter (in Julian calendar).

Transcription

Letter 84: 31 January 167 1/2, Flamsteed to Collins

[…] all the times I have veiwed the sun I could never see any Macula upon him but his whole disck. perfectly cleare. […]

Letter 85: 5 February 167 1/2, Flamsteed to Oldenburg

[…] Thursday last being February 1st instant was very cleare so that veiwing the sun severall times I found his body cleare from spots. […]

Letter 87: 10 February 167 1/2, Flamsteed to Collins

[…] all these diameters were observed in my tube of 164 1/2 inches, at none of these times [January 5, 9, 10, 11, 12, 15 and February 1] could I find any spot under the sun but hee has beene constantly cleare. […]

Letter 268: 27 July 1676, Flamsteed to Moore

Honored Sir

Whilest I was takeing some altitudes of the sun this morneing to correct the times of my last nights observations, I found upon his face a considerable large spot. which because it was the firs I ever saw, and a thinge you have not yet beene acquanted with I thought it might be no unwelcome novelty to enforme you of: the notes I tooke of it were these:

hor. corr.
h ′ ″
9.51.25	Macula a limbo Solis proximo.	710 = 5 – 43 ML
9.55	distantia Az: limbi Solis dextri et Mac.	1380 = 11 – 21 MZ
10.03.45	eodem distantia	1383 = 11 – 22 MZ

These notes I dare not affirme to be very praecise, because the wind sometimes shooke the tube, and groweing stronger would not permit me to measure the ☉s diameter which therefore I have derived from my former observations. $31'. 46''$

hence the distance of the spot from the ☉s Centr.	10.10 ☉M
from the verticall passeing by it	4.31 MA
The parallactick Angle at $10^{\mathrm{h}}.03$ 3/4′ by calculation I find	43∘.55 1/2′:
Hence the spot in Consequence of the Suns center	9′.34″ ☉e
with south latitude from it	3.25 1/2 e.M

I have drawne the figure of this spot and its position as it appeared through the tube, inverted: hold but the bottom of the paper upwards and you have the true appearance with its due position in respect of the ecliptick and verticall then passeing by the suns center.

The diameter of the spot in its broadest place was equall to ♃s or $50''$. its length not wholly double. about 1 1/3′.

It seemed a little cloven in the middle and had two thin cloudy spots following it like those in the figure.

It has not yet measured over above 1/3 part of its way through the sun. so that I suppose wee may see it yet 8 days if it breake not and dissipate before it have finished its jorney over his face which I much suspect, by reason that it seemed to part in its middle. I am apt to thinke the small spots following it were but parts of it broken off from it, and that therefore it was much larger whilest on the other side of the sun: [...]

Letter 274: 11 December 1676, Flamsteed to Towneley

[...] I can salve the severall appearances of the spot that appeared in the sun in October to the 24 or 25. Returned againe the 9 of November and after a revolution past came againe upon him the 6th Instant where you will find it till the 18th or 19th. [...]

Letter 450: 29 May 1682, Flamsteed to Molyneux

[...] As for spots in the sun I have never seene more then two the first in August 1676 which was large but broke into peeces and almost disappeared before it had passed through the visible diske of the sun. another in October November and December following I observed which was more Compact and made three revolutions before it was dissolved yet there was no large one. [...]

Letter 512: 2 May 1684, Flamsteed to Molyneux

[…] I tell you that this day was sevennight being the 25 of. Aprill in the morneing as I was takeing the distance of ☿ from the sun I discovered a large spot entred a little within the following limbe of his diske, the time of theire semirevolutions is 13 dayes and more then an halfe: but on the 10th of April at Noone I observed his Meridional distance from the vertex it was then cleare scarce 15 dayes before and I am confident there was then no spot on his face so that this certeinely had its rise in his latent hemisphere tis neare 7 1/2 yeares since I saw one before they have of late beene so scarce how ever frequent in the days of Galileo and Scheiner By the next dayes observations I stated its longitude in the suns diske from his aequinoctiall Colure and from thence determined in what pointes of his face it would be visible till it passed of his limbe into his opposite superficies these I give you in the Included figure: On the 8th of May in the Morneing it passes out of his diske, and if it have consistence enough to hold a second revolution it will be seene entred his following limbe againe on the 22 describeing a line very neare streight in its passage over him. The Theory of the spots is briefly delivered in my preface to the Doctrine of the Sphere inserted into Sir Jonas Moores workes, where I suppose the revolution of any point in the sun ad fixas to be compleate in 25 dayes six hours praecise. […]

Letter 519: 8 July 1684, Flamsteed to Bernard

[…] The magnitude and consistency of the spot emerging from the Sun seems to me to be such that I believe it may still last for another solar rotation. If it does, it will appear again visibly on the limb of the Sun’s disc on the 13th of this present July, and it will be seen inside it, [moving] towards the following limb, on the 14th. I think that this one spot will not last for three solar rotations, but that two or more have arisen, having spewed themselves forth in the vicinity of the first; or rather, if indeed you would see [how] I am brought to my opinion, that Etna-like mountains have been raised up from the thick subcutaneous matter of the Sun. For during the second revolution I saw two quite large spots almost two minutes apart, with rather pale companions in the second revolution. In the shape of these, observed in the middle of the Sun, neither the first or the newest that I observed can in any way be re-established. […]

Letter 745: 3 May 1698, Flamsteed to Leigh

[…] As for Spots in the Sun there have been none since the Year 1684. you may acquaint Mr. Ayres of it and that which is published in the forreigne prints is a Romance. the sun haveing been as clear of late yeares as ever, and I have seldom omitted Observeing him at Noon when it was clear. […]

Letter 747: 19 May 1698, Flamsteed to Leigh

[…] I told you in my last no spots have been seen in the Sun since 1684 all the storys you have heard of them are a Scilly Romance Spread by such as call themselves witty men to abuse the Credulous and not to be heeded J F. […]

Letter 905: 3 July 1703, Flamsteed to Sharp

I returne an imediate Answer to yours of the 29th past because this week since Monday last I have seene spots in Sun. which tho they are no novelty to me may be so to you they are advanced a little beyond the middle of the sun so that if this letter meets with a speedy conveyance you may find them before they turne out of him tho they change their shape dayly which makes me thinke they are shallow and will scarce continue another revolution.

Wee have seene of them ever since the middle of May and in June one of them returned that was a pretty dense one I expec[t] to see it within his antecedent limbe againe this day or tomorrow. [...]

Letter 906: 8 July 1703, Flamsteed to Lister

[…] Wee have seen great variety of spots in the sun. since May last. On tuesday last he was cleare and had none. but I expect a return of some this day. there is nothing to be learnt by them more then we know already and therefore. I should not have mentiond this but that since the year 1684 to the present I have seen none on him.