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Triangulum Galaxy (NGC 598) & Caldwell 18 (NGC 185)
Kristen Brink & Taylor Noordewier

Triangulum Galaxy Caldwell 18
Triangulum Galaxy- Kristen Brink Caldwell 18- Taylor Noordewier

A galaxy is a massive collection of gas, dust, and billions of stars that is held together by gravity. Earth is part of the Milky Way galaxy, however the Milky Way is just one of numerous galaxies in space. In fact, the amount of total galaxies have not been identified by scientists because there are so many.

Around 3 million light years from Earth one can find NGC 598, also known as the Triangulum Galaxy. This particular galaxy is also nicknamed the Pinwheel Galaxy because of its curved, oval shaped structure. It is located in the constellation Triangulum that is approximately 55,000 light years across. It is the third-largest member of the local group of galaxies which also includes the Milky Way, the Andromeda Galaxy, and about 50 other smaller galaxies. It was most likely discovered by Giovanni Hodierna around 1654, however it is credited to Charles Messier who discovered it in 1764.

NGC 185, also known as Caldwell 18 is a dwarf spheroidal galaxy. As the name suggests, it is a galaxy with low luminosity. A dwarf spheroidal galaxy usually has little to no dust and has no new star formation; however, NGC 185 is an exception because it has been observed to have a few young stellar clusters. It is located approximately 2.08 million light years away from Earth in the constellation of Cassiopeia. This particular galaxy is credited to Martinez-Delagado, Aparcio, and Gallar in 1999.

Both the Triangulum Galaxy and Caldwell 18 are in the Local Group; as mentioned before the Local Group is comprised of approximately 50 galaxies, one being the Triangulum galaxy, and one being the Andromeda galaxy that Caldwell 18 satellites. Being a galaxy, they encompass both young and old stars as well as have new star formation.

The two objects differ in that the Triangulum galaxy is a spiral galaxy, whereas Caldwell 18 is defined as a dwarf spheroidal galaxy. Although the Triangulum galaxy is approximately a million light years further than Caldwell 18, the Triangulum galaxy is one of the largest galaxies in the Local Group, therefore it can be seen much more clearly. While the Triangulum galaxy is dominated by younger, bluer stars because of the presence of gas and dust; Caldwell 18 has much older stars mostly at the center because of its lack of gas and dust.


Dwarf spheroidal galaxy (n.d.). In Wikipedia. Retrieved November 22, 2016.

Harvard-Smithsonian Center for Astrophysics . (2002, June 4). NASA Spitzer Telescope Reveals Pinwheel Galaxy's Hidden WondersIn SpaceRef. Retrieved November 22, 2016.

Local Group (2016, November 16). In Wikipedia. Retrieved November 22, 2016.

Lodriguss, J. (n.d.). NGC 185 and NGC 147. In Catching The Light. Retrieved November 22, 2016.

NASA Space Place. (2015, September 8). In NASA. Retrieved November 12, 2016.

Triangulum Galaxy (2016, November 16). In Wikipedia. Retrieved November 12, 2016.

Object Triangulum Galaxy (NGC 598) Caldwell 18 (NGC 185)
Right Ascension (J2000) 01:33:51 00:38:49
Declination (J2000) +30:39:36 +48:17:51
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), R (Red), V (Green)
Exposure time per filter B (195s), C (195s), R (180s), and V (120s) B (400s), R (200s), and V (200s)
Image dimension 720 x 666 pixels; 15.6 x 14.43 arcminutes 868 x 665 pixles; 18.81 x 14.41 arcminutes
Date/time observed October 4, 2016, 10:21:15 UT October 4, 2016, 09:03:41 UT



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