Caroline Herschel's Deep Sky Objects

Besides and before assisting her brother, William Herschel, in his great Deep Sky survey starting in late 1782, Caroline Herschel herself was an avid astronomical observer, and discoverer of comets (she originally found 8 of them) and deepsky objects. William Herschel has included her discoveries in his catalog, and assigned numbers to them.
CH     MH  M     NGC       Herschel   RA       Dec     Con  Type   R  Discovery Date

CH 12 14 NGC 189 - 00:39.6 +61:04 Cas OC O 1783 Sep 27 (Hoskin 2005) CH 9 4 M110 NGC 205 H V.18 00:40.4 +41:41 And G E5p I 1783 Aug 27 CH 11 9 NGC 225 H VIII.78 00:43.4 +61:47 Cas OC O 1783 Sep 27 CH 10 5 NGC 253 H V.1 00:47.6 -25:17 Scl G Sc I 1783 Sep 23 CH 20 6 NGC 659 H VIII.65 01:44.2 +60:42 Cas OC O 1783 Sep 27 CH 13 11 NGC 752? H VII.32 01:57.8 +37:41 And OC I 1783 Sep 29 CH 2 1 NGC 2360 H VII.12 07:17.8 -15:37 CMa OC O 1783 Feb 26 CH 5 2 M 48 NGC 2548 H VI.22 08:13.8 -05:48 Hya OC I 1783 Mar 8 CH 8 3 NGC 6633 H VIII.72 18:27.7 +06:43 Oph OC I 1783 Jul 31 CH 16 12 NGC 6819 - 19:41.3 +40:11 Cyg OC O 1784 May 12 (Hoskin 2005) CH 7 10 NGC 6866 H VII.59 20:03.7 +44:00 Cyg OC O 1783 Jul 23 (Hoskin 2005) CH 19 8 NGC 7380 H VIII.77 22:47.0 +58:06 Cep OC+N O 1787 Aug 7 CH 14 7 NGC 7789 H VI.30 23:57.0 +56:44 Cas OC O 1783 Oct 30 [CH 21] - IC 4665 - 17:46.3 +05:43 Oph OC I 1783 Jul 31 (Hoskin 2006)
Notes Key
  • CH: Caroline Herschel's number
  • MH: Michael Hoskin (2005) number
  • M, NGC, Herschel: Number in the Messier, NGC, and Herschel catalog
  • RA, Dec: Right Ascension and Declination for epoch J2000.0
  • Con: Constellation
  • Type: Object Type: OC, Open Cluster; OC+N: Open Cluster with Nebula, G: Galaxy (with Hubble type),
  • R: Remark on discovery: O: Original discovery, I: Independent rediscovery, -: No discovery (erroneous assignment)
  • Discovery Date
  • "Mystery" object, possibly discovered by Caroline Herschel:
    CH  4  13       [NGC 2349] H VII.27   07:10.8  -08:36  Mon  OC?    O  1783 Mar  4 (Hoskin 2005: WH's mis-id)
    
    Note: Unidentifyable Caroline Herschel Deepsky Objects:
    CH 17            Near Chi Aurigae, nebulous
    CH 18            RA 01:40:28, Dec -13, 3..5 or more nebulous stars
    
    Note: Dismissed objects previously listed as possible discoveries:
    [-CH 12] 14     [NGC  381] H VIII.64  01:08.3  +61:35  Cas  OC     -  1783 Sep 27 (Hoskin 2005: WH's mis-id)
    [-CH  9] 15     [NGC  891] H V.19     02:22.6  +42:21  And  G Sb   -  1783 Aug 27 (app. W.H.'s 1st cat; W.H. Smyth)
    [-CH  2] 16     [NGC 2204] H VII.13   06:15.7  -18:39  CMa  OC     -  1783 Feb 26 (appendix to W.H.'s 1st catalog)
    
    Notes: Finally, Michael Hoskin reports (Hoskin 2006) that Caroline has probably independently rediscovered IC 4665 but assigned it to William, who in turn had assigned it to her: IC 4665 had been discovered earlier twice: First by Philippe Loys de Chéseaux before 1746, and second by Johann Elert Bode before 1782. The first discovery got published only in 1892, while the second one appeared in 1782, hidden in Bode's "Vorstellung der Gestirne," which the Herschels were unaware at the time of this rediscovery. But somehow, neither Caroline nor William managed to get this discovery in one of their catalogs, so it got welknown only in 1908 by its inclusion in the second IC catalog, based on its 1908 rediscovery by Solon I. Bailey!

    Sources:

    Michael Hoskin (Hoskin 2005, in some cases corrected according to Hoskin 2006) discloses some more detail about Caroline's deepsky observations. Here follows her list of discoveries, with date and identification:
    No. 1. Feb 26, 1783. M93.
    Caroline thought to have discovered a new cluster near the star 7 (Zeta) Navis (Puppis), which was probably mis-read 1 (Rho) and therefore not immediately identified with M93. [MH No. 17]
    No. 2. Feb 26, 1783. H VII.12 = NGC 2360.
    Caroline's first real original discovery of a deepsky object. [MH No. 1] In the appendix to his first catalog, William confused this one with H VII.13 = NGC 2204. [MH No. 16]
    No. 3. Mar 4, 1783. M46.
    [MH No. 18]
    No. 4. Mar 4, 1783. H VII.22 = NGC 2349 ??
    [MH No. 13]
    No. 5. Mar 8, 1783. H VI.22 = M48 (NGC 2548).
    [MH No. 2]
    No. 6. Apr 6, 1783. M29.
    [MH No. 19]
    No. 7. Jul 23, 1783. H VII.59 = NGC 6866.
    [MH No. 10]
    No. 8. Jul 31, 1783. H VIII.72 = NGC 6633.
    [MH No. 3]
    No. 9. Aug 27, 1783. H V.18 = M110 (NGC 205).
    [MH No. 4] In the appendix to his first catalog, William confused this one with H V.19 = NGC 891. Based on this entry, William Smyth attributed the latter to Caroline. [MH No. 15]
    No. 10. Sep 23, 1783. H V.1 = NGC 253.
    [MH No. 5]
    No. 11. Sep 27, 1783. H VIII.78 = NGC 225.
    [MH No. 9]
    No. 12. Sep 27, 1783. NGC 189.
    [MH No. 14]
    No. 13. Sep 29, 1783. H VII.32 = NGC 752?
    [MH No. 11]
    No. 14. Oct 30, 1783. H VI.30 = NGC 7789.
    [MH No. 7]
    No. 15. Feb 23, 1784. Re-observation of NGC 225.
    Cluster 1 1/4 deg south following Kappa Cas, viewed again March 8 and 11, according to Hoskin (2005), footnote No. 97. Missing the identity may have resulted from a misprint; On Feb 23, Caroline noted erronously that this cluster would precede, instead of follow, Kappa Cas. William Herschel probably quotes this observation as discovery when he writes "CH 1784" in his catalog, while the original discovery was her No. 11.
    No. 16. May 12, 1784. NGC 6819.
    [MH No. 12]
    No. 17. Oct 13, 1782. "Chi Aurigae or near it is nebulous."
    Not identifyable by this description.
    No. 18. Dec 1, 1782. "1h 40' 28" RA & 13deg S Dec are 3. 4. 5 or more small stars which I cannot help thinking make a nebulous appearance."
    Not identifyable by this description.
    No. 19. Aug 7, 1787. H VIII.77 = NGC 7380.
    [MH No. 8]
    No. 20. Sep 27, 1783. H VIII.65 = NGC 659.
    [MH No. 6]
    Michael Hoskin also reports (Hoskin 2005) that Caroline had avidly observed more objects, which she identified as known nebulae or clusters. A list extracted from his article follows: In her notes, letters and diaries, Caroline states to have observed 14 objects until the end of 1783 (Buttmann 1961, p. 64, Mary Herschel 1876). Two followed in 1784, and one further in 1787.

    Caroline Herschel's objects include the conspicuous spiral galaxy NGC 253, and the famous elliptical M110 (NGC 205), the second satellite of the Andromeda galaxy, M31. The other objects are all open clusters: Bright M48 (NGC 2548), four of the open clusters in Cassiopeia and one in nearby Cepheus, NGC 752 in Andromeda, one in Canis Major and two in Cygnus. There's a big gap of populated Right Ascensions between RA 8:15 and 18:25, so that all Caroline Herschel objects can be observed easily in one night on the Northern hemisphere, about Northern Fall.

    Caroline Herschel was honored lately by the astronomical community by naming a Lunar Crater after her: C. Herschel (34.5N, 31.2W, 13.0 km diameter, 1935). Asteroid (281) Lucretia was named to honor Caroline Lucretia Herschel; it had been discovered on October 31, 1888 by J. Palisa in Vienna.

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    References


    Please submit any additions, corrections, or comments. Especially, one source gave the number of 14, but didn't identify them, so, if you can, please help me with the remaining single one entry.


    Hartmut Frommert
    Christine Kronberg
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    Last Modification: March 5, 2014