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NGC 2366

Not visible to the naked eye and approximately 10 million light years away in the constellation Camelopardalis, lies the quirky Dwarf Irregular Galaxy NGC 2366. This galaxy's classification as 'Irregular' comes from the fact that it has no definite structure to it, like the spiral arms of Spiral Galaxies; while NGC 2366's classification as 'Dwarf" comes from, as you may expect, its small size compared to other galaxies. In fact, two galaxies like NGC 2366 known as the Large Magellanic and Small Magellanic clouds orbit our Milky Way galaxy! The are several interesting features of NGC 2366, such as the bright H-II region classified as Markarian 71 (which is the defined bright oval in the gray scale image above) in the southern portion of the galaxy and the nearby galaxy NGC 2363 (which is the hazy cloud directly to the left of Markarian 71) both of which are active star forming regions. A star known as a Luminous Blue Nova was discovered in 1996 inside Markarian 71 that is roughly 60 times the mass of our Sun

Due to the dim nature of NGC 2366, it is impossible to bring out the colors of the galaxy in the image above with a relatively short exposure time on Calvin College's telescope in Rehoboth, NM. The studying of this galaxy and ones like it offers insight as to how such dim galaxies can be hosts to such intense star-forming activity.

The above color image was taken by Steve Leshin with a 32.5 hour exposure in association with the Lowell Observatory. Color images taken of galaxies offer insight into the the galaxy indicating where stars are forming, and how old they are! (For reference Markarian 71 is the pinkish region on the right side of the blue disk while NGC 2363 is directly above it.) To understand the meaning of the colors we need to understand what the ionization of an atom is. To ionize an atom, a lot of radiation and heat must excite and "expel" the electron from the atom, but the electron does not stay this way forever and when the electron recombines with the atom it will give off a light particle with a specific frequency which can be perceived as visible light, and in the case of Hydrogen this color is red/pink. So where we see that red/pink color in this image tells us that the light is coming from radiation of hot stars interacting with a nearby gas cloud. From this color too is how Astronomers conclude that Markarian 71 and NGC 2363 are star forming regions. The rest of the galaxy's light is being produced by the stellar populations within it which appears blue, and this indicates that a lot of the stellar populations within NGC 2366 are cosmologically young and much hotter than our Sun. From a stellar evolution standpoint, this also means that the stellar populations are capable of fusing much heavier elements than our Sun too, and are more likely to end their lives in massive Supernova explosions!

Given that Markarian 71 (Mrk 71) is a star forming region, I took particular interest in calculating its Luminosity and Physical Size. By analyzing how many pixels across the star forming region was and using a scale factor of 1.32 arc seconds per pixel, it has a linear size of about 900 light-years which corresponds to an angular size of .308 arc minutes. The distance to this object is estimated to be 3.21 Mpc (ned.ipac.caltech.edu); we find the Major Axis to have an angular size of 3.94 arc minutes, which corresponds to a physical size of 11900 light-years and we find the Minor Axis to have an angular size of 0.666 arc minutes , which corresponds to a physical size of 2030 light-years.

 

To calculate Luminosity, I performed Photometry on my image to get its apparent brightness. This works by by comparing the unknown object it to many reference stars of known luminosity. Using ten reference stars MaxIM calculated that Mrk71's apparent brightness is 13.647. From my own calculations its luminosity is about 30 million times the luminosity of the Sun.

References:

Blumenthal, George, Brad Smith, Stacy Palen, and Laura Kay. 21st Century Astronomy. 4th Ed., New York, W.W. Norton & Company, 2013.

Dressen et al. "A New Luminous Blue Variable in the Giant Extragalactic H II Region NGC 2363." The SAO/NASA Astrophysics Data System. 

"[DRR96] NGC 2363 VI" SIMBAD Astronomical Database <http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%5BDRR96%5D+NGC+2363+V1>

Nemiroff, Robert and Jerry Bonnell. "Bright Stars, Dim Galaxy." Astronomy Picture of the Day. <https://apod.nasa.gov/apod/ap961014.html>

"NGC 2363A." SIMBAD Astronomical Database <http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Mrk%2071>

"NGC 2366." NASA/IPAC Extragalactic Database. <http://ned.ipac.caltech.edu/>

Usher, Oli "Hubble observes a dwarf galaxy with a bright nebula" <https://www.spacetelescope.org/news/heic1207/>

Wikipedia, "NGC 2366"

Color Image Credit:

https://lowell.edu/research/lari-pro-am-astronomy/

 

Right Ascension (J2000) 07:28:55
Declination (J2000) +69:12:57
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B (300s x 10), C (300s x 6), R (300s x 3) V (300s x 5)
Image dimension 1092x736 pixels; 24.02x16.19 arc minutes
Date/time observed March 14, 2017 02:18 UT

In order to produce a clear and crisp image there is a process to take the initial images the telescope takes to the final image, which involves subtracting using provided bias, dark, and flat frames. Each of the frames accounts for bias of the CCD camera, eliminate thermal noise, and nonuniform CCD illumination. To do this we align and stack all of the Bias frames in MaxIM DL 5, which we save as our "Master Bias" image. Then we take all of the Dark frames and calibrate them using the Master Bias image, and stack all of our dark frames to create a "Master Dark" image. Then for the Flats images (in each color filter) we calibrate it using the Master Dark Frame, then stack them all just as before. Finally using these corrected Bias, Dark, and Flat frames we can create a "Master Image" for each color filter which can then be stacked on top of one another to produce the final color image. For the image I have a 1 multiplier for Red, 1.4 multiplier for Green, 1.8 Multiplier for Blue. I used a Luminosity weight of 15% and a Gamma value 1.

 

 

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