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

NGC 189 was found by Caroline Herschel on September 27, 1783. As William Herschel misidentified it with NGC 381 (see below), he never observed or cataloged this object; it as never seen again until October 27, 1829, when John Herschel independently discovered it and cataloged it as h 36.
NGC 225 was cataloged again by Caroline Herschel on February 23, 1784, and cataloged as her No. 15. It was this second discovery which was quoted by William Herschel in his catalog.
NGC 6819 was not seen or cataloged by William Herschel. After its discovery by Caroline, it was next seen and independently discovered by Karl Ludwig Harding somewhen before 1824, and by John Herschel on July 31, 1831.

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:

NGC 2349, discovered by Caroline and cataloged by William Herschel as H VII.27, was confused by John Herschel in the GC, who logged the position of a close double star; this position found its way into the NGC. Consequently, the RNGC found it to be not a deepsky object and listed it as missing, a classification repeated in the NGC 2000.0. Harold Corwin finally cleared up the error in his NGC Bugs list. Nevertheless, the present author [hf] is inconclusive about NGC 2349's nature as a physical cluster. Despite all this, Hoskin (2005) dismisses this object as a misidentification by William Herschel because of position mismatch by more than 4 degrees.

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:

The descriptions are too vague for an identification (Hoskin 2006)

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:

Two objects were misassigned to Caroline by William Herschel in the appendix to his first catalog: H V.19 (NGC 891) for H V.18 (M110), and H VII.13 (NGC 2204) for H VII.12 (NGC 2360). Caroline had never claimed to have discovered these objects.
As her second finding of September 27, 1783, Caroline described a cluster which matches NGC 189, an object William never saw. William identified it with his H VIII.64 (NGC 381), probably because of confusing two stars (Hoskin 2005). NGC 189 was never seen again until October 27, 1829, when John Herschel independently discovered it and cataloged it as h 36.

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:

On July 31, 1783, Caroline wrote: "From Beta Serpentarii [Beta Oph] towards S [71 Oph], 1 1/3 degree; a cluster of stars. I counted about 50 in the field; rather more or less. (My Brother's)."
The same evening, William wrote: "Cluster of Stars. 1 1/3 degree from Beta Serpentarii towards S. It consists of about 14 to 16 large ones with several very small ones between. 7ft compound [eye]piece. Lina found them."

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:

Unless otherwise noted, the Caroline Herschel findings were looked up in John Herschel's General Catalogue (John Herschel, 1864).
In a posting to the Netastro Catalog email list (netastrocatalog-announce at atmob.org), William C. Bryson points out that from above list, NGC 891 and NGC 2204 might be mis-assignments (this email is also source of the NGC 2204 entry in this page; thanks !).
Newer information has been included from Michael Hoskin's recent work on Caroline Herschel's astronomical observations (Hoskin 2005); Hoskin also dismisses the two objects NGC 891 and 2204, together with NGC 381 and NGC 2349 which he finds misidentifications by William Herschel.
Eventually, Michael Hoskin recovered Caroline's catalog, which had been believed lost previously, in a large folder labelled "Index" (Hoskin 2006). Here the folder is presented as a list of 20 numbered entries manually written by Caroline on a single piece of paper!

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:

M27 on September 30, 1782 and on April 6 and July 23, 1783;
"a nebula under Phi Aurigae" on October 13, 1782; in that region of the sky there are the three Messier clusters M36, M37 and M38;
M13 and M37 on October 29, 1782;
M44 on January 23, 1783;
M47 and M41 on February 26, 1783; note she observed, recorded and identified M47 despite this was later found to be a "missing" Messier Object! She mentions another observation of M47 of March 4, 1783 when she erroneously cataloged M46 as her No. 3; one might speculate if this her error might be related to Messier's wrong position for M47;
M67 on March 26, 1783;
M56 on April 7 and May 4, 1783;
M4, M9 and M23 on May 5, 1783;
M5 (which she first took for a comet), M10, M11 and M12 on May 22, 1783;
M14 on July 21 and 23, 1783; on the latter date, besides once more viewing M27, she also found M71 and on that day, discovered NGC 6866;
M2, M16, M25 and M55 on July 30, 1783.

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.

Links

Short biography of Caroline Herschel
Biography of Caroline Herschel (School of Mathematics and Statistics, University of St Andrews, Scotland)
Sketches of some Caroline Herschel Objects, by Jane Houston Jones
Jane has also sketched Moon Crater C. Herschel.
Jane has published her observations, partly based on informations of this list, in a contribution to Sky and Telescope (Jones 2002).

References

Günther Buttmann, 1961. Wilhelm Herschel, Leben und Werk. [William Herschel, Life and Work]. Wissenschaftliche Verlagsgesellschaft m.b.H., Stuttgart, 1961.
John Frederick William (John) Herschel, 1864. Catalogue of Nebulae and Clusters of Stars. Philosophical Transactions of the Royal Society (London), Vol. 154, pp. 1-137. [ADS: 1864RSPT..154....1H]
Mrs. John Herschel [Mary Herschel], 1876. Memoirs and Correspondence of Caroline Herschel. With portraits [of Caroline and William Herschel]. John Murray, Albemarle Street, London. The remark is found on p. 52, as quoted from Caroline:
"[..] I knew too little of the real heavens to be able to point out every object so as to find it again without losing too much time by consulting the Atlas. But all these troubles were removed when I knew my brother to be at no great distance making observations with his various instruments on double stars, planets, &c., and I could have his assistance immediately when I found a nebula, or cluster of stars, of which I intended to give a catalogue; but at the end of 1783 I had only marked fourteen, when my sweeping was interrupted by being employed to write down my brother's observations with the twenty-foot. [..]"
Michael Hoskin, 2005. Caroline Herschel as Observer. Journal for the History of Astronomy, Vol. 36, Part 4, No. 125, pp. 373-406 (November 2005). [ADS: 2005JHA....36..373H]
Michael Hoskin, 2006. Caroline Herschel's Catalogue of Nebulae. Journal for the History of Astronomy, Vol. 37, Part 3, No. 128, pp. 251-253 [ADS: 2006JHA....37..251H]
Jane Houston Jones, 2002. The Caroline Herschel Objects. Sky and Telescope, Vol. 104, No. 5 (November 2002), pp. 107-111.

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
[contact]

Last Modification: March 5, 2014