Dwarf Elliptical Galaxy M32
|Observation data (J2000 epoch)|
|Right ascension||00h 42m 41.8s|
|Declination||+40° 51′ 55″|
|Redshift||-200 ± 6 km/s|
|Distance||2.49 ± 0.08 million light-years (763 ± 24 kpc)[a]|
|Apparent magnitude (V)||8.08|
|Apparent size (V)||8′.7 × 6′.5|
|Notable features||satellite galaxy of the
|M 32, NGC 221, UGC 452, PGC 2555, Arp 168, LEDA 2555|
Messier 32 (also known as NGC 221 and Le Gentil) is a dwarf elliptical galaxy about 2.65 million light-years away in the constellation Andromeda. M32 is a satellite galaxy of the famous Andromeda Galaxy (M31) and was discovered by Le Gentil in 1749. M32 measures only 6.5 ± 0.2 thousand light-years  in diameter at the widest point. Like most elliptical galaxies, M32 contains mostly older faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the relatively recent past. 
The structure and stellar content of M32 is difficult to explain by traditional galaxy formation models. Recent simulations suggest a new scenario in which the strong tidal field of M31 can transform a spiral galaxy into a compact elliptical. As a small spiral galaxy falls into the central parts of M31, most of the outer layers of the smaller spiral are stripped away. The central bulge of the galaxy is much less affected and retains its morphology. Tidal effects trigger a massive star burst in the core, resulting in the high density of M32 observed today. There is also evidence that M32 has an outer disk. Although usually M32 is thought to be a satellite galaxy as mentioned above, recently a report suggested the possibility that M32 is actually a normal galaxy instead of a dwarf with triple distance compared with the data stated above, and actually located outside the Local Group with only their position on the sky overlapped.
At least two techniques have been used to measure distances to M32. The infrared surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to M32 using this technique is 2.46 ± 0.09 million light-years (755 ± 28 kpc). However, M32 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to M32 using this technique is 2.51 ± 0.13 million light-years (770 ± 40 kpc). Averaged together, these distance measurements give a distance estimate of 2.49 ± 0.08 million light-years (763 ± 24 kpc).[a]
- ^ average(755 ± 28, 770 ± 40) = ((755 + 770) / 2) ± ((282 + 402)0.5 / 2) = 763 ± 24
- "NASA/IPAC Extragalactic Database". Results for NGC 221. Retrieved 2006-11-29.
- Jensen, Joseph B.; Tonry, John L.; Barris, Brian J.; Thompson, Rodger I.; Liu, Michael C.; Rieke, Marcia J.; Ajhar, Edward A.; Blakeslee, John P. (2003). "Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations". Astrophysical Journal. 583 (2): 712–726. arXiv:. Bibcode:2003ApJ...583..712J. doi:10.1086/345430.
- Karachentsev, I. D.; Karachentseva, V. E.; Hutchmeier, W. K.; Makarov, D. I. (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
- Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6.
- "SIMBAD-M32". SIMBAD Astronomical Database. Retrieved 2009-11-29.
- Armando, Gil de Paz; Boissier; Madore; Seibert; Boselli; et al. (2007). "The GALEX Ultraviolet Atlas of Nearby Galaxies". Astrophysical Journal Supplement. 173 (2): 185–255. arXiv:. Bibcode:2007ApJS..173..185G. doi:10.1086/516636.
- Diameter = distance × sin(diameter_angle) = 6.5 ± 0.2 thousand light-years. diameter
- Kepple, George Robert; Sanner, Glen W. (1998). The Night Sky Observer's Guide. Vol. 1. Willmann-Bell. p. 17. ISBN 0-943396-58-1.
- Rudenko, Pavlo; Worthey, Guy; Mateo, Mario (2009). "Intermediate age clusters in the field containing M31 and M32 stars". The Astronomical Journal. 138 (6): 1985–1989. Bibcode:2009AJ....138.1985R. doi:10.1088/0004-6256/138/6/1985.
- Bekki, Kenji; Couch, Warrick J.; Drinkwater, Michael J.; Gregg, Michael D. (2001). "A New Formation Model for M32: A Threshed Early-Type Spiral Galaxy?". Astrophysical Journal Letters. 557 (1): L39. arXiv:. Bibcode:2001ApJ...557L..39B. doi:10.1086/323075.
- Graham, A. W. (2002). "Evidence for an Outer Disk in the Prototype Compact Elliptical Galaxy M32". Astrophysical Journal Letters. 568 (1): L13. arXiv:. Bibcode:2002ApJ...568L..13G. doi:10.1086/340274.
- Young, K. S. et al. (2008), A critical review of the evidence for M32 being a compact dwarf satellite of M31 rather than a more distant normal galaxy
- Valluri, M.; Merritt, D.; Emsellem, E. (2004). "Difficulties with Recovering the Masses of Supermassive Black Holes from Stellar Kinematical Data". Astrophysical Journal. 602 (1): 66–92. arXiv:. Bibcode:2004ApJ...602...66V. doi:10.1086/380896.
|Wikimedia Commons has media related to Messier 32.|
- "StarDate: M32 Fact Sheet"
- "SEDS: Elliptical Galaxy M32"
- Merrifield, Michael. "M32 – Dwarf Elliptical". Deep Sky Videos. Brady Haran.
- Messier 32 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images