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NGC 404 Galaxy & Caldwell Galaxy C17
Shayla Pollock & Sara Wright

NCG404 Caldwell 17
NGC 404 - Shayla Pollock Caldwell C17 - Sara Wright

A galaxy "is a huge collection of gas, dust, and billions of stars and their solar systems" and is held together by gravity ("What Is"). A galaxy ranges in sizes and has three main shapes including spiral, elliptical, and irregular ("Galaxy"). Galaxies are alone, within pairs, or in clusters. Scientists are divided over how galaxies have come to form in these variations (Society). The word galaxy itself comes from the Greek word "galaxias" which means "milky," so the name is based on the observation of our own galaxy the Milky way ("Fun Facts"). Galaxies all fall within groups. We have studied galaxy groups by looking at our own--the Local Group. The Local group is a group of galaxies that includes the Milky Way, the Andromeda, and around 30 other galaxies. These all move relative to one another ("Fun Facts").

NGC 404 is a small lenticular galaxy in the Andromeda constellation. A lenticular galaxies is a type of irregular galaxy that typically has little dust or gas and contains old stars, but NGC 404 is unusual in that it is full of gas. It also has a ring of gas around it. It is an isolated galaxy, meaning that it's relatively far away from other galaxies (Seligman). It's been nicknamed "Mirach's Ghost." This is because it can be difficult to see because of the glare from Mirach, a bright star that is only 7 arcminutes away from the galaxy ("Mirach's Ghost (NGC 404)"). William Herschel discovered it in 1784.

Caldwell C17 (or NGC 147) is about 2.58 M light-years (ly) away and is within the constellation Cassiopeia (Wikipedia).  This galaxy is a satellite of the Andromeda Galaxy. Caldwell C17 is a part of the Local Group. However, Caldwell C17 is categorized as a dwarf elliptical/spheroidal galaxy with the diameter of 4,400 ly across (Normandin).  Elliptical galaxies are stars shaped as an elliptical disk ("Fun Facts"). This galaxy is unique in its size, the fact that its neighboring galaxy is closely related, and both are satellites of the Andromeda.  The luminosity is low and the brightness is very faint (Normandin).  

The similarities found between NGC 404 and Caldwell C17 is that they are both galaxies. NGC 404 and Caldwell C17 are both relatively close to each other and to our own galaxy, the Milky Way. Both galaxies are considered to be dwarf galaxies, as they are both relatively small in star count compared to their counterparts in their galaxy groups. In order to be considered a dwarf galaxy, the galaxy needs to have approximately 10 million stars. A regular sized galaxy contains approximately 100 trillion stars ("Fun Facts"). Both galaxies contain old stars and are in the Local group.

In NGC 404, the color found is a bluer shade. This suggests that there are stars found in this galaxy formation are younger. Caldwell C17 has a much more defined shape as elliptical whereas NGC 404 has a lenticular shape. This definition of the elliptical galaxy provides better clues about the approximate age of the stars whereas the age of NGC 404 is harder to determine upon first look. This is because elliptical galaxies are known to be older galaxies ("Fun Facts"). NGC 404 is also larger than Caldwell C17. NGC 404 almost has a twice as large diameter of approximately 10,000 ly across compared to that of Caldwell C17 which is 4,400 ly across (Seligman).

References:
"Fun Galaxy Facts for Kids." Fun Galaxy Facts for Kids. Science Kids, 8 July 2016. Web. 29 Nov. 2016.

 "Galaxy." Wikipedia. Wikimedia Foundation, n.d. Web. 15 Nov. 2016.

"Mirach's Ghost (NGC 404)." Encyclopedia of Science, edited by David Darling. Accessed 15 Nov. 2016.

Normandin, George P. "NGC 147, a Dwarf Elliptical Galaxy." NGC 147, a Dwarf Elliptical Galaxy. Kopernik Space Images, n.d. Web. 22 Nov. 2016.

“NGC 147.” Wikipedia. Wikimedia Foundation, 25 Oct. 2016. Web. 22 Nov. 2016.

Seligman, Courtney. "NGC 400-449." New General Catalog Objects, edited by Courtney Seligman. 8 Apr. 2016. Accessed 29 Nov. 2016.

Society, National Geographic. "Galaxies." National Geographic. N.p., n.d. Web. 15 Nov. 2016.

"What Is a Galaxy?" NASA. NASA, 8 Sept. 2015. Web. 15 Nov. 2016.

Object NGC 404 Galaxy Caldwell C17 Galaxy
Right Ascension (J2000) 01:09:26 00:33:11
Declination (J2000) +35:43:06

+48:30:26

Filters used B (Blue), R (Red), V (Green) B (Blue), R (Red), V (Green)
Exposure time per filter B (800), V (800s), and R (180s) B (800s), V (800s) , and R (180s)
Image dimension 302x201 pixels; 3.27x2.18 arcminutes 828x416 pixels; 8.97x4.51 arcminutes
Date/time observed October 04, 2016, 10:10 UT October 04, 2016, 08:31 UT

 

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