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Astronomical Observatory: Cool Images

Astr110 Photography Projects, Fall 2004

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M15, Megan Thomassen

Helix Nebula

M15 was discovered by Jean-Dominique Maraldi in 1746. It was catalogued by Charles Messier on June 3, 1764, which is why it is called M15, the M signifying that it is a Messier object. Messier catalogued many objects, so there are a lot of M objects in our sky. M15 is globular star cluster, about 170 light years across, and it is approaching us at a rate of 107 km/second. It is 360,000 times brighter than our sun, and, for one last random fact, it contains nine pulsars, which is a high number for one star cluster.

M15 is a beautiful globular star cluster. You can easily see the globular nature of the cluster in the photo, as opposed to an open star cluster. The bright star in the upper left corner is designated SAO 107179. Regrettably, the data from the red filter image for this photograph was damaged, so it was unable to be included, otherwise you could see more red color in some of the stars, especially those towards the outside. As it is, you can faintly some blue in the stars, which means that they are younger and hot.


Bennet, Jeffery, Megan Donahue, Nicholas Schneider, and Mark Voit. The Cosmic Perspective. 2nd ed. New York: Addison Wesley, 2002.


Right Ascension (J2000) 21:30:00
Declination (J2000) +12:10:00
Filters used Blue, green, and clear
Exposure time per filter 300 seconds for Blue, 60 seconds for Green, 30 seconds for Clear







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