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Astr110 Photography Projects, Spring 2005

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M100, Esther Flink


The M100, a spiral galaxy, was discovered by Pierre Mechain on March 15, 1781. Its position was obtained by his friend, Charles Messier, on April 13, 1781. Of all the galaxies in the Virgo Cluster of galaxies, the M100 is one of the brightest. It can be found in the spring constellation Coma Berenices.

The M100 has two mains arms spiraling out from its center (containing bright blue stars) and several fainter arms. As seen from this image, there is a lack of symmetry in its brightest features. This suggests that it has been disturbed by gravitational interactions with its neighbours. The bright knots in the spiral arms are large nebulae where star formation is actively taking place.

This galaxy can be viewed easily through a moderate-sized amateur telescope, and is angled nearly face-on with Earth. However, the M100 is much larger than shown here, which is apparent through deep photographs of the galaxy. From the above photgraph, its estimated angular size is 5.2' x 4.7'. This measurement is slightly smaller than measurements found on the SEDS: M100 web site, which state the M100's size as 7' x 6'. This difference in measurements may be due to the fact that a significant portion of the galaxy lies in its faint outer regions and escapes discovery in conventional images.

The M100 has a distance of 60 million ly (light years) and a linear size of approximately 92000 ly.


SEDS: M100

SEDS: Messier 100

Astrophotography: Messier 100


Right Ascension (J2000) 12:22:55.2
Declination (J2000) 15:49:23
Filters used clear(C)
Exposure time per filter

300 seconds in C

Date observed

April 1, 2005 (C)