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NGC 2403
Melissa Sorrentino


Approximately 11 million light-years from Earth lies a brilliant spiral galaxy named NGC 2403. Spiral galaxies are the most common types of galaxies. Spiral galaxies contain long arms extending from a central bulge. Some spiral galaxies have loosely wound arms, while others have arms that are tightly wound. Typically, spiral galaxy arms contain high concentrations of gas and dust, and are often areas of new and constant star formation. The bulge of a spiral galaxy, on the other hand, is typically composed of old stars. Very little star formation occurs in the central bulge.

NGC 2403 is a beautiful island universe that makes its home within the Northeast corner of the constellation Camelopardalis. This galaxy is among one of the Northern objects that Charles Messier missed when compiling his catalog of galaxies. It was instead discovered by William Herschel in 1788 (Frommert&Kronberg). NGC 2403 is an intermediate Spiral Galaxy, noted as SAB. Being an interemediate Spiral Galaxy, it is in between the classifications of a barred spiral and an unbarred spiral. Bars are bright lines, or bar-shaped structures, composed of stars that run through the center of a galaxy. NGC 2403 has a slight bar visible. The sprial arms of NGC 2403, which are relatively open, can be seen in the above picture, marked with a purple/blue coloring.

NGC 2403, measuring approimately 50,000 light years across, is home to many giant star forming HII regions. The spiral arms are home to much dust and molecular gas. The dominant blue coloring of the spiral arms is due to the high concentration of massive, luminous, young stars. High mass stars live for a short time and emit hot radiation that is blueish in color. The reddish globs that can be observed in the spiral arms are the glow of atomic hydrogen gas. These are giant star forming HII regions, where active star formation is taking place. The ionized hydrogen gives off light at various wavelengths as the electron drops down from excited energy states. The most common energy drop emits red light. The yellow glow in the middle bulge is a site of older stars, where current formation is not taking place.

The HII regions are filled with hot, massive stars that explode as bright supernovae at the end of their short lives. In 2004, one of the brightest supernovae discovered in recent times was found in NGC 2403. The bright supernova emits the light of 200 million suns (Hubblesite, NASA). The supernova is located within a cluster of massive, predominately blue, stars. The cluster, named Sandage-96, has a total mass of about 24,000 times the mass of the Sun. The cluster is so far away that light of the cluster's stars blends together to form the appearance of one massive star. (Hubblesite, NASA). However, the explosion is the closest stellar explosion that has been discovered in more than a decade.

The distance to NGC2403 is estimated to be 11 million light years from earth (Hubblesite,NASA); I calculated a maximum angular size of 15.13 arcminutes, which corresponds to a linear size of approximately 48,000 light years.

Non-optical image:

Hi disk

The above non-optical image of NGC2403 (on the left) was taken with the VLA C array, with a total integration time of 48 hours, and covers an area of about 40 arcminutes X 40 arcminutes. The optical image on the right was taken from the Digitized Sky Survey. The type of observation was Spectral Line Observation.
What the images are depicting is a side-by-side view of the optically visible NGC 2403 (right) with the radio wave view (left). As was previsoulsy noted, NGC 2403 contains a large disk of hydrogen gas. The gas emits radio waves that can be detected with radio telescopes. The two images are on the same scale. The gas disk adds to the galaxy significantly, extending well beyond the optical galaxy. The gas disk holds to the same spiral structure as the optical galaxy, and also shows large holes resulting from the supernovae explosions that take place inside NGC 2403.
The images clearly show how complex our universe is, with there defintely being "more than meets the eye". The complexity and intricacy of the Spiral Galaxy NGC 2403 points to none other than the magnificent handiwork of our Creator God. Studying this galaxy has put me even more in awe of how grand our Designer truly is.


HubbleSite, NASA, "Galaxy NGC 2403: Before and After Supernova 2004dj Outburst", n.d. Web. 26 Apr. 2017.

Hubblesite, NASA, "News - A Bright Supernova in the Nearby Galaxy NGC 2403.". N.p., n.d. Web. 26 Apr. 2017.

Kopernik Space Images, "Spiral Galaxy NGC 2403 - Supernova 2004dj."  n.d. Web. 26 Apr. 2017.

Kronberg, Hartmut & Frommert, Christine. "NGC 2403" N.p., n.d. Web. 26 Apr. 2017.

Nemiroff, Robert & Bonnell, Jerry, "Astronomy Picture of the Day: NGC 2403 in Camelopardalis." NASA. NASA, 23 July 2011. Web. 26 Apr. 2017.

Nemiroff, Robert & Bonnell, Jerry, "Astronomy Picture of the Day: NGC 2403 in Camelopardalis ." NASA. NASA, 27 March 2015. Web. 26 Apr. 2017.

NRAO Image Gallery,"NRAO: National Radio Astronomy Observatory." . N.p., n.d. Web. 26 Apr. 2017.

Sloan Digital Sky Survey, "Spiral Galaxies", n.d. Web. 26 Apr. 2017.

Right Ascension (J2000) 07:36:50.59
Declination (J2000) 65:36:05.9
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B (300s x 9), V (300s x 5), and R (120s x 18); C (60s x 16)
Image dimension 1092x736 pixels; 23.8x16.1 arcminutes
Date/time observed

March 17, 2017, 06:00 UT

April 3, 2017, 02:35 UT (R filter)


Data reduction is "the process of taking the raw data and processing it to remove the effects of CCD bias, thermal noise, and nonuniform CCD illumination". Maxim was used to combine and reduce all images received from the telescope for the varying filters. Data reduction was done for each individual frame. Begnning with bias, all the frames were dragged onto MaxIm. The images were animated together to make sure there were no drastic brightness differences between them. This was then repeated for the darks and flats as well. After those steps were taken, the bias only frames were opened. The images were stacked and combined (setting the Combine Method to Average and setting FITS Format to 16-bit Int, and Normalization to None). After inspecting the stacked bias frames, the result was saved as Master Bias. A Master Dark was then created after using the Master Bias to bias-correct the dark frames (this was done through calibrating). Then, going one filter at a time, Master Flats were created. These were done using the Master Bias and Master Dark and callibrating them to the master frames in order to bias-correct and dark-correct the flat frames.
Once master frames were created, filter-by-filter, data frames were reduced. This was done by opening all data frames for a specific filter into MaxIm. When choosing Set Calibration, a window appeared. The Flat, Bias, and Dark groups were added.The Master Flat image was added. Under the Dark group, the Dark Frame Scaling menu was set to Auto-Optimize. Then, all was callibrated. The reduced images for this filter were then saved. The same steps were repeated for the remaning filters.
After Masters were created and data frames were reduced, a color image was created. All four master images were openened in MaxIm. Under the Color Menu, Combine Color was selected and “Allow Resize” and “Bgd Auto Equalize” were both checked. In the three drop-down menus labeled “Red”, “Green”, and “Blue”, the images corresponding to these three colors were selected. The Clear filter was assigned to Luminance. The strength of each color was selected, with Red being 1, Green being 1.5, and Blue being 2. The Luminance weight was set to 80%, and the saturation of the image was adjusted to 115%. After adjustments, the image was visually appealing and looked natural when compared to other published images of NGC 2403. The final image was saved.

(Procedure based off of lab sheets provided by Jason Smolinski)



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