Messier 110

Right Ascension	00 : 40.4 (h:m)
Declination	+41 : 41 (deg:m)
Distance	2670 (kly)
Visual Brightness	8.5 (mag)
Apparent Dimension	17x10 (arc min)

Discovered by Charles Messier in 1773.

Messier 110 (M110, NGC 205) is the second brighter satellite galaxy of the Andromeda galaxy M31, together with M32, and thus a member of the Local Group of Galaxies.

Curiously, this galaxy was discovered by Charles Messier on August 10, 1773, as described in the Connaissance des Tems for 1801, and depicted on his fine drawing of the "Great Andromeda Nebula" and its companions published his memoir of these nebulae in 1807 (Messier 1807). However, Messier did never himself include this object in his catalog, due to unknown reasons, perhaps a certain sloppiness in recording. It was the last additional object, added finally by Kenneth Glyn Jones in 1966. Independent of Messier's discovery, Caroline Herschel independently discovered M110 on August 27, 1783, little more than 10 years after Messier, and assigned it to her small list under No. 9. William Herschel numbered it H V.18 when he cataloged it on October 5, 1784.

The small elliptical galaxy M110 is at about the same distance as the Andromeda galaxy M31; we adopt a value of 2.67 million light years which is a little more than M31's 2.6 Mly. It was confirmed as a galaxy near M31 by Walter Baade in 1944, when he resolved it into stars (Baade 1944). It is of Hubble type E5 or E6 and is designated "peculiar" because it shows some unusual dark structure (probably dust clouds). M110 is now often classified as a dwarf spheroidal galaxy, not a generic elliptical one (this would make it the first ever known dwarf spheroid, of course). However, as it is much brighter than typical dwarf spheroids, Sidney van dan Bergh has recently introduced the term "Spheroidal Galaxy" for this and similar galaxies, including Local Group members NGC 147 and NGC 185. M110's mass was estimated to be between 3.6 and 15 billion solar masses.

Apparently, despite its comparatively small size, this dwarf elliptical galaxy has also a remarkable system of 8 globular clusters in a halo around it. The brightest of them, G73, is of about 15th magnitude and thus within the reach of large amateur telescopes; Steve Gottlieb has observed it with a 44-cm telescope together with M31 globulars, and amateurs at the Ferguson Observatory near Kenwood, CA obtained a CCD image showing 7 of them with their 14-inch Newtonian and CB245 CCD camera (via the M31 GC images page).

NGC Online data for M110

References

• Walter Baade, 1944. The resolution of Messier 32, NGC 205, and the central region of the Andromeda Nebula. Astrophysical Journal, Vol. 100, pp. 137-146 (September 1944) [ADS: 1944ApJ...100..137B].
• Charles Messier, 1807. Observations et dessin de la grande et belle nébuleuse de la ceinture d'Androméde, la première qui fut découverte, et de deux petites nébuleuses, l'une au-dessus de la grande et le seconde au-dessous, vues dans une lunette qui renverse, comme le dessin. Rec. Inst., Vol. 8 (Mém. de l'Institut, Premier Semestre de 1807), 1807, pp. 206-213 + Plate [Bibcode: 1807RecIn...8..206M]. Translation available online.

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Hartmut Frommert
Christine Kronberg
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Definitive Version: October 14, 2013
Last Modification: January 5, 2024