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NGC 628 (Spiral Galaxy) & NGC 925 (Spiral Galaxy)
Jesse Bergwerff and Jacob Horstman

NGC 628 NGC 925
NGC 628-Jesse Bergwerff NGC 925- Jake Horstman

Spiral galaxies are named from the distinct shape of their disks. In spiral galaxies, stars, gas, and dust are formed into spiral arms that protrude from the galaxy's center. Spiral galaxies consist of a lot of gas, dust, newly forming stars, as well as dark matter. Spiral galaxies have a lot of hot, young stars (blue, red, and yellow stars), meaning they are often among the brightest galaxies in the universe. "About 20% of all galaxies are spirals" (What is a spiral galaxy?). Earth is found in a spiral galaxy called the Milky Way.

NGC 628 is a beautiful example of a spiral galaxy, also called Messier 74. This galaxy displays a face on view allowing the viewer to see it in its entirety.  “Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars and glowing pink regions of ionized hydrogen (hydrogen atoms that have lost their electrons). These regions of star formation show an excess of light at ultraviolet wavelengths.  Tracing along the spiral arms are winding dust lanes that also begin very near the galaxy's nucleus and follow along the length of the spiral arms” (NASA, 2011).  To locate the galaxy look to the constellation Pisces, also known as the fish.  Roughly 32 million light years away, NGC 628 “is the dominant member of a small group of about half a dozen galaxies” (NASA 2011).  The group's name is M74 with just “about 100 billion stars, making it slightly smaller than our Milky Way” (NASA, 2011).

The Spiral Galaxy NGC 925 is approximately 30 million light years away. It has two spiral arms coming from the center of the galaxy. "The center of the galaxy resembles a bar in which the two arms protrude from. It can be found in the Triangulum constellation" (Martin, 2014). NGC 925 has a low surface brightness so it appears to be dim in the sky. There is a 10 million solar mass (M☉) cloud of neutral hydrogen connected to NGC 925. It is uncertain whether this is a satellite dwarf galaxy. The galaxy is inclined at an angle of 55° to the line of sight. (Wikipedia) This angle makes it appear to be greatly slanted in the night sky.

When looking at the bulge of each galaxy both bulges appear to be very yellow in color. Both galaxies have star-forming regions and have dense gas clouds that surround and protrude around/from the bulge. Both of these galaxies are a part of constellations. NGC 925 is found in the constellations Triangulum and NGC 628 is found in the constellation Pisces. Each galaxy is a part of a galaxy group; NGC 925 is a part of the NGC 1023 group. NGC 628 is a part of the cluster M74 group which consists of 5 to 7 galaxies which includes a few irregular galaxies.

NGC 925 looks to have four tightly wound spiral arms whereas NGC 628 has many arms that are tightly around and protrude from the bulge. Both galaxies have star-forming regions but NGC 925 has more regions that are closer to the bulge of the galaxy. NGC 628 has fewer star-forming regions that are located in arms of the galaxy away from the bulge. NGC 925's stars appear to be cooler in temperature because they are more red and yellow in color. NGC 628 stars are hotter in temperature because they are blue. Blue stars are relatively hotter than red and yellow stars.

References:

Martin, M., & Martin, J. (2014, February 26). NGC 925. In Best of AOP. Retrieved November 19, 2015, from http://www.noao.edu/kpvc/observers/n925.html

NASA, . (2011, December 16). Spiral Galaxy . In NASA. Retrieved November 19, 2015, from
              http://www.nasa.gov/multimedia/imagegallery/image_feature_2132.html

NASA. (2014). Spiral Galaxy 74. In Hubble's site.org. Retrieved December 3, 2015.

NGC 925. (2008, December 8). In Wikipedia. Retrieved November 19, 2015, from https://en.wikipedia.org/wiki/NGC_925

What is a spiral galaxy?. NASA, n.d. Web. 8 Dec. 2015. <http://coolcosmos.ipac.caltech.edu/ask/217-What-is-a-spiral-galaxy

 

Object NGC 628 NGC 925
Right Ascension (J2000) 1:36:41.8 02:27:16.913
Declination (J2000) 15:47:01 33:34:43.97
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B (2x300s), V(150s), and R(150s); C (300s) B (2x300s), V(150s), and R(150s); C (300s)
Image dimension 294x260 pixels; 23.8x16.1 arcminutes 371x260 pixels; 19.5x21.2 arcminutes
Date/time observed October 15, 2015, 3:23 ET Septemeber 29, 2015, 3:00 ET

 

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