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Elliptical Galaxy (Messier 110) & Sprial Galaxy (M101)
Becky Ajuonuma & Eyram Kpodo

M110 M101
Messier 110 - Becky Ajuonuma Messier 101 - Eyram Kpodo

Some of the most majestic sites of our universe are galaxies. According to Bennett, galaxies are defined as "islands of stars in space containing millions, billions, or even trillions of stars all held together by gravity and orbiting a common center" (Bennett, 182). They are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies, and "they range in size from dwarfs with just a few thousand (103) stars to giants with one hundred trillion (1014) stars" (Wikipedia).

Messier 110 is a dwarf elliptical galaxy located about 2.9 million light years away. It is also a satellite of the Andromeda Galaxy (Wikipedia). Messier 110 is one of the two bright galaxies of the Andromeda galaxy and has an apparent magnitude of 8.5 and an angular diameter of 17x10 arc-minutes (Espenak). It was discovered by Charles Messier in 1773 but was never included in his catalog for unknown reasons. However, outside of Messier’s discovery, Caroline Herschel also discovered M110 in 1783 (Seds USA). Messier 110 is an interesting and unique galaxy. For a dwarf elliptical galaxy of its size, Messier 110 has a "remarkable system of 8 globular clusters in a halo around it" (Seds USA). Although it is well known that elliptical galaxies lack gas and dust to form new stars, M110 actually contains young stars and faint dust clouds, which are observed as unusual dark structures (NASA).

M101 is also known as the Pinwheel Galaxy. It is a spiral galaxy located in the constellation of the Big Dipper (Wikipedia). It was discovered by Pierre Mechain on 27th March, 1781. On 28th February, 2006 NASA released a detailed image of M101. It has a diameter of about 170,000 light years, roughly equal in size with the Milky Way galaxy (NASA, 2015). One of the main characteristics of M101 is that it has lot of HII regions which are located on the spiral arms of the galaxy. HII region is a region of large, low-density clouds of partially ionised gas, in which there has been recent star formation (Wilson Fich, 1999).The stars formed in the HII region are usually blue stars that are short-lived. These stars release very large amounts of ultraviolet light which ionise the surrounding gas. M101 is also characterised as asymmetrical due to the tidal forces from interactions from its surrounding companion galaxies (Waller, 1996). The gravitational interactions compress interstellar hydrogen gas. This gas is what catalyzes the formation of stars in the spiral arms of M101. The activity can be detected by through ultraviolet images (Wikipedia). M101 has a black hole of 20 - 30 solar masses (Liu, Bregman, 2013).

M110 and M101 are similar in a couple of ways. M110 and M101 both have a bulge and a halo. They also both have old stars present; spiral galaxies have a mix of old and young stars while elliptical galaxies have mainly old stars. Furthermore, both galaxies have interacted with some galaxies in their surrounding. This is why M101 is asymmetrical in shape and M110 displays some brightness (Waller 1996). Finally, both galaxies have some structure to them. Although their structures are different, they are not like irregular galaxies with no structure.

M110 and M101 are also different in a number of ways. M110 is an elliptical galaxy while M110 is a spiral galaxy. This means they are structurally different. M110 has no disk or spiral arms while M101 does and M110 has little gas and dust while M101 is rich in gas and dust. Another difference between the two galaxies is size. M101 is larger in size compared to M110; M110 is a dwarf galaxy,17,000 light years in diameter while M101 is 170,000 light years in diameter. Additionally, M101 is asymmetrical (due to its gravitational interactions with its companion galaxies) while M110 is not, and M101 has a black hole while M110 does not. Finally, both galaxies have different star forming regions. The young stars in the unique M110 are found in the center of the galaxy while the young blue stars in M101 are found in the spiral arms of the galaxy.


  • Bennett, Jeffrey O. "Galaxies." The Cosmic Perspective Fundamentals. San Francisco, CA: Pearson Addison-Wesley, 2010. 182. Print.
  • Espenak, Fred. "Messier 110.", 29 June 2011. Web. 08 Dec. 2015.
  • Liu, Ji-Feng, Joel N. Bregman, and Stephen Justham. "Puzzling accretion onto a black hole in the ultraluminous X-ray source M 101 ULX-1." International Weekly Journal of Science (2013). Print.
  • "Messier 110." Messier Object 110. Seds USA, 14 Oct. 2013. Web. 27 Nov. 2015.
  • "Messier 110." Wikipedia. Wikimedia Foundation, 27 Aug. 2015. Web. 10 Dec. 2015.
  • Schedler, Johannes. "Astronomy Picture of the Day." APOD. NASA, 8 Sept. 2006. Web. 27 Nov. 2015.
  • Wilson, C. D., and M Fich. "Star formation in the giant HII regions of M101." Cornell University Library. N.p., 23 Mar. Web. 9 Dec. 2015.
  • Waller, William H., Ralph C. Bohlin, and Michael Fanelli. "Ultraviolet Signatures of Tidal Interaction in the Giant Spiral Galaxy, M101." Cornell University Library. N.p., 17 Dec. Web. 9 Dec. 2015.
Object Messier 110 Messier 101
Right Ascension (J2000) 12:30:49 14:03:12
Declination (J2000) +12:23:26 +54:20:58
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B (200s x 2), V (150), R (150s), and C (250s x 2) B (300s x 2), V(300s x 2), and R (250s x 2), C (250s x 2)
Image dimension

984 x 659 pixels; 21.3x14.3 arcminutes

1092 x 736 pixels; 24.8 x 15.9 arcminutes
Date/time observed October 14, 2015, 03:26 UT October 2, 2015 02:34 UT



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