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Astr110 Photography Projects, Fall 2005

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M74, Mary Margaret Pierson and Lindsey Geelhoed

M74

M74

M74 is a spiral galaxy included in the Messier catalog. It was discovered by Pierre Méchain in 1780. A galaxy is a huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity. This particular galaxy is made up of about 100 billion stars. It is 30 million light-years away from our galaxy, the Milky Way, and is moving away from us at approximately 754 kilometers per second. M74 is a type Sc galaxy. The S stands for spiral. It is type Sc because its center is rather small, its spiral arms are loosely wound around the center and the distribution of the stars appears a bit clumpy. M74 is the chief member of a small group of rather strange galaxies including the irregulars UGC 1176, UGC 1195, UGCA 20; the SBa barred spiral galaxy NGC 660, and the Sm galaxy UGC 891 which is a cross between a spiral and an irregular galaxy.

It is sometimes difficult to find M74 in the sky, but a close up look is definitely worth it. It is described by the Astronomy Picture of the day website as “the Perfect Spiral” this may be because it is nearly perfect in its symmetry and is also very photogenic. Its symmetry is most likely the result of density waves sweeping across M74's disk caused by gravitational attraction of nearby galaxies. In the night sky, M74 is not visible if any light pollution is present. A small telescope would probably only be able to show the brightness of its centre, making it look like a star instead of a galaxy. In fact, it was accidentally cataloged as a star in the “Bonner Durchmusterung” by F.W. Argelander in 1860.

There have been two observed supernovas in M74. The first, Supernova 2002ap was observed by a Japanese amateur named Yoji Hirose on January 29, 2002. It was classified as a “hypernova” which occurs when stars of at least 40 times the size of the sun explodes. The second named Supernova 2003gd was observed visually by Bob Evans on June 12, 2003 in Australia . This supernova was Type II..

The colors in this photo of M74 allow us to learn more about this galaxy. The green and blue smudges are artifacts. The numerous gray-blue clumps in the spiral arms are groups of young, bright stars. The density of the stellar dust allow for many new stars to form, hence the reason that most of the younger stars are located in the spiral arms. The pink regions are stars shining through diffused gas and dust clouds known as ionization nebulae, also referred to as HII regions. There are one hundred and ninety three HII regions in M74. We calculated its angular size to be 660” and this translates into the linear size of 110 thousand light-years.

References:

Nemiroff, Robert , and Jerry Bonnell. "M74:The Perfect Spiral." Astronomy Picture of the Day . 24 May 2003. NASA. 2 Dec. 2005 NASA.

Frommert, Hartmut, and Christine Kronberg. M74 . 16 Nov. 2005. 2 Dec. 2005 Messier.

Bennett, Jeffrey, Megan Donahue, Nicholas Schneider, and Mark Voit. The Cosmic Perspective . 3rd ed. San Francisco : Pearson Education Inc, 2005.

Right Ascension (J2000) 1h 36m 42.0s
Declination (J2000) +15 ° 47' 00"
Filters used blue(B), green(V), red(R)
Exposure time per filter 300 seconds in BVR
Date observed

November 05, 2005 (RV)
November 19, 2005 (B)