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M66 (NGC 3627)

Nathan Slager


Messier 66, located more than 36 million light years away, sits at the common center of mass of the Leo Trio. It can actually be spotted with a regular pair of 5x30 binoculars on a clear night’s sky. Charles Messier first catalogued it on March 1, 1780 after he missed it in 1773 due to a comet (the comet of 1773 and 1774) that had passed in front of the galaxy. M66 stretches across nearly 100,000 light years, about the same length as our galaxy, the Milky Way. In addition, four supernovae have been spotted within M66.

A recent collision between M66 and a nearby galaxy within the Leo Triplet most likely explains the asymmetrical arms and high concentration of star forming regions. At some point in the future the three galaxies in the trio will merge to form a single massive galaxy. The colorful purples and blues emitting from the galaxy indicate regions of hot gas forming brand new stars. On the contrary, the gray and brown light depict dust lanes within the galaxy's arms. To see another perspective of M66, please visit Given the image above, the length of M66 was calculated to be 53,000 light years across its major-axis.

Surface Brightness Profile:

In order to quantify the brightness of M66 beginning from the center and going outwards, the following brightness profile below was created using Maxim DL, excel and logger pro.

An exponential profile adequately provides a model for the brightness of M66 as seen in the equation above ( Ie * exp(-x/R) + C ). From the fit obtained the scale radius(R or Rs) was calculated to be about 0.3 +/- 0.007 kpc or about ten times smaller than our Milky Way Galaxy (~3.5 kpc).The range of Rs values span from 1 kpc up to 50 kpc for spiral galaxies, whereas irregular Galaxies usually have a scale radius of a few kpc. The deviation from the exponential model is a result of the spiral arms of M66. The rest of the data fit the model very well, pointing to an exponential relationship between surface brightness and radial distance.

Image Processing:

The final image went through a series of processes in order to produce the final result. The first was a subtraction from a bias image which is taken at the same temperature as the actual but with a negligible exposure time. This eliminates initial bias from the image. Similarly, a dark image with a comparable exposure time is subtracted from the image in order to eliminate further bias. Finally, a flat image is taken for each filter to zero out filter specific bias. Next, each filter was combined to create a color image. This image's colors were rebalanced to bring out the blue and purple regions of star formation. The ratios for the color matrix can be found in the table below. Finally, the image was adjusted for saturation.

Red 0.9 - -
Green - 1.25 -
Blue - - 6.5


"Astronomy Picture of the Day." APOD: 2010 April 13. N.p., n.d. Web. 13 May 2015.
Filmer, Joshua. "Astronomy Picture of the Day: 10/13/13 – M66." N.p., 13 Oct. 2013. Web. 13 May 2015.
"Galaxy Properties (a Thumbnail Sketch)." N.p., n.d. Web. 13 May 2015.
"Messier 66." Universe Today. N.p., 18 Aug. 2009. Web. 13 May 2015.
Trosper, Jaime. "Astronomy Photo of the Day (APotD): 10/3/14 — Messier 66 (M66)." N.p., 03 Oct. 2014. Web. 13 May 2015.


Right Ascension (J2000)


Declination (J2000) +12:59:42.0
Filters used B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter C, B, V and R (300s)
Image dimension 1092x736 pixels; 21.5x14.5 arcminutes
Date/time observed March 21, 2015 10:00 P.M. UT




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