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Astr111 Photography Projects, Fall 2009

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M77, Caitlin Buddingh


This object, M77, is what is known as a spiral galaxy. Like our own galaxy, the Milky Way, M77 is a typical spiral galaxy consisting of four main parts. Spiral galaxies typically consist of a nuclear bulge, a halo, a disk, and spiral arms. There is a whole lot going on in spiral galaxies. They usually have old and new stars contained within their systems, as well as new star formation. The bright hot stars are most easily seen in the spiral arms. Globular clusters of stars are often visible in the outer halos of the spiral galaxies. The reason for the interesting shape of the spiral galaxies, as well as for the spiral arms all going in a particular direction is that the galaxies are actually rotating!

M77 in particular was discovered in 1780 by Pierre Mechain who at the time clasified it as a nebula. This galaxy is now classified as one of the largest in Messier's catalog, and is a lovely galaxy with a yellowish tinge. It is yellowish because young stars are blue, and old stars are red, and when stars are middle aged, or if you have a mix of old and new stars like in this galaxy, then there is a yellow color of black body radiation. If you click on the image, you will find an oversaturated image that shows you just how large the galaxy actually is, you can see a faint ring that surrounds the galaxy for another inch around the image. This is the lowest density region of the galaxy. The spiral arms, three ow which can be clearly picked out, are a middle region of density of stars, while the bright center of the galaxy is the highest density region. One could imagine living on a planet in the middle of this galaxy and having the sky full of stars, or on the outer rim of the low density region and having quite a dark sky at night. M77 is about 60 million light years distant from our planet, and is estimated that the inner disk is the size of 27 billion solar masses, while the total galaxy is more on the order of one trillion solar masses. The linear size of M77 is 1.23x10^11. M77 is noted because when astronomers look at its spectrum of light, it shows a great deal of broad emission lines. This indicates that the galaxy is extremely bright, and rapidly expanding. It is one of the most active galaxies in its class.


Fraknoi, Morrison, and Wolff. Voyages to the Stars and Galaxies. 3rd ed. United States: Brooks/Cole, 2004. 386. Print.

Frommert, Hartmurt, and Christine Kronberg. "Messier 77." seds.org Voyages to the Stars and Galaxies. N.p., 2 Sept. 2007. Web. 2 Dec. 2009. <http://seds.org/messier/m/m077>.


Right Ascension (J2000) 02:42.7
Declination (J2000) -00:01
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 5x60 seconds in C, B,V,R
Date observed