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NGC 6503 & Firework Galaxy (NGC 6946)
Sung Hun Choi & Tiffany Marthin

NGC6503 NGC6946
NGC 6503 - Sung Hun Choi Firework Galaxy - Tiffany Marthin

A galaxy is "a great island of stars in space, containing millions, billions, or even trillions of stars, all held together by gravity and orbiting a common center" (Bennett, 2015:G-5). There are different kinds of galaxies: Elliptical, Spiral, S0, and Irregular Galaxies. Our objects, NGC 6503 and NGC 6946 are spiral galaxies. The four main elements of spiral galaxies are a bright central bulge, spiral arms, a thin disk, and a spherical halo (Bennett, 2015). The bulge looks yellowish and is usually consisting of old stars. The arms are consisting of cool gas and dust, which implies existence of star formation.

NGC 6503 is a field dwarf spiral galaxy with diameter of approximately 30,000 light-years. It lies about 18 million light-years away and is located at the edge of a strangely empty, separated place of space known as the Local Void. This galaxy is situated in the constellation of Draco. The central area of NGC 6503 is special in that it is a type known as a “Low Ionization Nuclear Emission Region,” or LINER, which emit less lights than other galaxies (Jager, 2015). Its colorful arms show that there are old red stars mixed with newly forming blue stars.

NGC 6946 (“Fireworks Galaxy”) is an intermediate spiral galaxy with approximately 40,000 light-years diameter and is about 22 million light years away from Earth (Boen, 2013). It was found by William Herschel on September 1798 and it is located in the constellation Cepheus (“NGC”, 2015). NGC 6946 is a unique galaxy because during the last 100 years, there have been nine Supernovae (the death explosions of massive stars) that were observed in this galaxy. In fact, three of the oldest supernovas that have been found were detected in NGC 6946 and that is how this galaxy got named “Fireworks Galaxy” (“List of Supernovae”, n.d.).

Moreover, it is interesting to see some similarities of NGC 6503 and NGC 6946 other than being in the same classification (Spiral Galaxy). First, from just seeing the picture, both galaxies have yellowish centers which indicate older stars, bluish spiral arms that indicate newly forming stars which mixed with red regions. Second, both galaxies appear to be “alone” in the field while most other galaxies are clumped together in groups or interact with each other (Plotner, 2008; Jager, 2015). Third, both galaxies also have the dark brown dust lanes, which indicates that there are a lot of older and denser regions where interstellar clouds may collapse to form new stars.

Despite of their similarities, NGC 6503 and NGC 6946 also have some significant differences. First, we only can see the side of NGC 6503 while we can see NGC 6946 with a face-on perspective. Second, NGC 6503 has an apparent magnitude of 10.2 while NGC 6946 has an apparent magnitude of 9.6 which means that NGC 6946 is seen brighter from the earth. This could be caused by the bigger size and closer distance of NGC 6946. Third, there are 9 supernovae that have been found in NGC 6946 while there is only one so far that has been found in NGC 6503 (“List of Supernovae”, n.d.).

References:

Bennett, Jeffrey, Megan Donahue, Nicholas Schneider, and Mark Voit. The Cosmic Perspective Fundamentals. 2nd ed. N.p.: Pearson Education, 2015. Print. Boen, Brooke. "NGC 6946: The 'Fireworks Galaxy'." NASA. N.p., 8 Nov. 2013. Web. 1 Dec. 2015.<http://www.nasa.gov/mission_pages/chandra/multimedia/fireworks-galaxy-ngc6946.html>.

Jager, Mathias. "Lost in Space - New Hubble Image of Galaxy NGC 6503." European Space Agency. N.p., 10 June 2015. Web. 1 Dec. 2015. <http://www.spacetelescope.org/news/heic1513/>

"List of Supernovae." IAU Central Bureau for Astronomical Telegrams. Central Bureau for Astronomical Telegrams, n.d. Web. 1 Dec. 2015. <http://cbat.eps.harvard.edu/lists/Supernovae.html>.

"M101: The Big Picture." The Hubble Heritage Project. N.p., n.d. Web. 3 Dec. 2015. <http://heritage.stsci.edu/2009/07/supplemental.html>.

“NGC 6946.” Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc. 5 Nov. 2015. Web. 19 Nov. 2015. <https://en.wikipedia.org/wiki/NGC_6946>.

Plotner, Tammy. "The Fire Cracker Galaxy - NGC 6946 by Dietmar Hager." Universe Today. N.p., 6 Sept. 2008. Web. 1 Dec. 2015. <http://www.universetoday.com/17824/the-firecracker-galaxy-ngc-6946-by-dietmar-hager/>.

 

 

Object NGC 6503 NGC 6946
Right Ascension (J2000) 17:49:27 20:34:52
Declination (J2000) +70:08:40 +60:09:13
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B (180s x 4), V (150s x 1), and R (150s x 1); C (180s x 2) B (150s x 4), V (150s x 1), and R (150s x 1); C (180s x 2)
Image dimension 402x250 pixels; 8.71x5.42 arcminutes 282x250 pixels; 6.11x5.42 arcminutes
Date/time observed October 01, 2015, 05:15 UT October 01, 2015, 07:44 UT and October 14, 2015, 02:10 UT

 

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