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)
"Mystery" object, possibly discovered by Caroline Herschel:
- 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.
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)
Unidentifyable Caroline Herschel Deepsky Objects:
- 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.
CH 17 Near Chi Aurigae, nebulous
CH 18 RA 01:40:28, Dec -13, 3..5 or more nebulous stars
Dismissed objects previously listed as possible discoveries:
- The descriptions are too vague for an identification
[-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)
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:
- 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
NGC 189 was never seen again until October 27, 1829, when John Herschel
independently discovered it and cataloged it as h 36.
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!
- 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."
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:
- 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
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:
- 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
[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,
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]
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
- 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
- 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),
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
- M2, M16,
M25 and M55
on July 30, 1783.
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.
- 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,
- 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
- Michael Hoskin, 2006.
Caroline Herschel's Catalogue of Nebulae.
Journal for the History of Astronomy, Vol. 37, Part 3, No. 128, pp. 251-253
- 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.
Last Modification: March 12, 2009