Royal Astronomical Society Herschel Archive [hereafter: RAS] W.1/1, 128–9.
2.
RAS W.4/1.3, 231. Herschel will catalogue it as “very bright nearly round planetary not well-defined disk”. We know it as NGC 7009. Cf. RAS W.2/1.4, 28v.
3.
RAS W.2/1.4, 29r.
4.
RAS W.4/1.3, 240; cf. W.2/1.4, 33r.
5.
RAS W.4/1.5, 400.
6.
RAS W.4/1.5, 419, cf. RAS W.2/1.6.
7.
RAS W.4/1.5, 430, cf. RAS W.2/1.6.
8.
RAS W.4/1.5, 445, cf. RAS W.2/1.7.
9.
RAS W.4/1.5, 446, cf. RAS W.2/1.7.
10.
RAS W.4/1.5, 459, cf. RAS W.2/1.7.
11.
RAS W.2/2.5, 53r.
12.
HerschelWilliam, “Catalogue of one thousand new nebulae and clusters of stars”, Philosophical transactions, lxxvi (1786), 457–99.
13.
RAS W.2/3.2, sweep 222; RAS W.2/1.9, 9r.
14.
RAS W.2/3.2, sweep 239; RAS W.2/1.9, 27v.
15.
RAS W.2/3.2, sweep 275; RAS W.2/1.10, 14v. Herschel would later regard as a planetary IV.14 in Aquila (NGC 6772), “very faint of equal light, resolvable, 1’ diameter, in the midst of numberless stars of the milky way”, which he came across on 21 July 1784. RAS W.2/3.2, sweep 242; RAS W.2/1.9, 30r.
16.
HerschelWilliam, “On the construction of the heavens”, Philosophical transactions, lxxv (1785), 213–66, discussed in Michael Hoskin, The construction of the heavens: William Herschel's cosmology (Cambridge, 2012).
17.
For example, when the French geologist Barthélemy Faujas de Saint-Fond described a night he spent at Datchet in August 1784, he wrote: “Mr. Herschel requested me to direct my principal attention to the stars which he was the first to discover to be of different colours from each other. …” The visit is described by Saint-Fond in his Travels through England, Scotland, and the Hebrides, i (London, 1799), 63–77.
18.
For more on this see SteinickeWolfgang, “Herschel, Uranus und die Planetarischen Nebel”, VdS-Journal, xxii (2007) 8–10. Steinicke kindly draws my attention to Herschel's observation of IV.1 on 8 Sept. 1792 with the 40-ft, where Herschel notes: “its light appeared of a greenish cast, but having been much exposed to the light of candles my eyes were not in a proper condition to judge impartially of colours”, RAS W.2/4.
19.
Hoskin, op. cit., chap. 4.
20.
Herschel, op. cit. (ref. 16), 265–6.
21.
RAS W.2/3.7, sweep 785.
22.
RAS W.2/3.7, sweep 819.
23.
RAS W.2/3.7.
24.
On 8 Aug 1787, RAS W.2/3.6, sweep 749.
25.
RAS W.2/3.7, sweep 853.
26.
RAS W.2/3.7, sweep 854.
27.
RAS W.2/3.7, sweep 920.
28.
HerschelWilliam, “Catalogue of a second thousand new nebulae and clusters of stars; with a few introductory remarks on the construction of the heavens”, Philosophical transactions, lxxix (1789), 212–55.
For a list of Herschel's ‘nebulous stars’, see Table 2.17 of SteinickeWolfgang, Observing and cataloguing nebulae and star clusters: From Herschel to Dreyer's New General Catalogue (Cambridge, 2010). As Steinicke remarks, it is surprising that IV.45 (NGC 2392), which Herschel had seen as long ago as 17 January 1787, had not then convinced him of the existence of ‘true nebulosity’.
32.
Ibid., 85.
33.
Ibid., 75.
34.
Ibid., 76.
35.
Ibid., 86–7.
36.
Constance A. Lubbock, original typescript of The Herschel chronicle (The Herschel Museum, Bath), XV, 24.
37.
RAS W.2/2.5, 53r.
38.
RAS W.2/2.5, 53v.
39.
Respectively h 2047 and h 2075 in his 1833 catalogue, “Observation of nebulae and clusters, made at Slough, with a 20-feet reflector, between the years 1825–1833”, Philosophical transactions, cxxiii (1833), 359–506. John Herschel says that these stars “suggest the idea of accompanying satellites. … The enormous magnitude of these bodies, and consequent probable mass (if they be not hollow shells), may give them a gravitational energy, which, however rare we may conceive them to be, may yet be capable of retaining in orbits, three or four times their own diameter, and in periods of great length, small bodies of a stellar character”. He recommends that “these satellites of planetary nebulae ought to be especially attended to” (p. 500). I thank Wolfgang Steinicke for this information. William Herschel noted on 18 September 1784, in the course of sweep 276, that IV.16 is “Between 2 stars of unequal brightness”, but he does not suggest that the stars are satellites. For the subsequent history of the theory, see Steinicke, op. cit. (ref. 31), 152–4.
40.
RAS W.2/2.5, 53r.
41.
HerschelWilliam, “Catalogue of 500 new nebulae, nebulous stars, planetary nebulae, and clusters of stars; with remarks on the construction of the heavens”, Philosophical transactions, xcii (1802), 477–528.
42.
Ibid., 501.
43.
Ibid., 502.
44.
RAS W.2/2.7, 5r and v. (In the CD these pages are wrongly reproduced after W.2/2.8.)
45.
RAS W.1/13.V.12.
46.
RAS W.1/1, 263–4.
47.
RAS W.2/2.7, 33r.
48.
Ibid., 32v.
49.
Ibid., 32v.
50.
HerschelWilliam, “Astronomical observations relating to the construction of the heavens, arranged for the purpose of a critical examination, the result of which appears to throw some light upon the organization of the heavenly bodies”, Philosophical transactions, ci (1811), 269–336; “Astronomical observations relating to the sidereal part of the heavens, and its connection with the nebulous part; arranged for the purpose of a critical examination”, Ibid., civ (1814), 248–84.
51.
Ibid., 271.
52.
As Herschel wrote in the memorandum for the 1802 paper (Figure 1), “there are steps that ally them [planetary nebulae] to clusters and others that seem to argue that they are derivatives of nebulous stars, perhaps both may be admitted”. He has, without good reason, moved IV.26 from the former to the latter category.
53.
“The sun, viewed in this light, appears to be nothing else than a very eminent, large, and lucid planet….” William Herschel, “On the nature and construction of the Sun and fixed stars”, Philosophical transactions, lxxxv (1795), 46–72, p. 63.
54.
In particular, the 40-ft had surely been intended to contribute to the debate as to whether or not true nebulosity could exist, and the observation had at a stroke robbed the great reflector of its raison d'être.
