M2 - Globular Cluster in Aquarius
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Globular clusters are among the most captivating objects in the night sky, attracting the interest of both professional astronomers and experienced observers. These tightly bound collections of tens or even hundreds of thousands of stars belong to the oldest populations in our Galaxy. Messier 2, also cataloged as NGC 7089, stands out as one of the most remarkable examples.
M2 was first noted in 1746 by the French astronomer Jean-Dominique Maraldi, who was observing a comet with Jacques Cassini when he came across a faint, hazy object that clearly wasn’t stellar in nature. In 1760, Charles Messier independently rediscovered the same spot of light during his search for comet-like objects and later added it to his catalog. At the time, he assumed it was a nebulous, starless cloud. It was not until 1783 that William Herschel managed to resolve the cluster into individual stars, revealing its true nature.
Under exceptionally dark and transparent skies, M2 can be glimpsed with the unaided eye. Through binoculars it appears as a soft, diffuse patch of light, while larger telescopes begin to tease out its rich stellar population. Its brightest members shine at about magnitude 6.5m, placing them within reach of even smaller amateur instruments.
Observations
November 10, 2025, around 11:00 PM – Katowice, Poland
urban conditions, very high level of light pollution
The cluster is located in the constellation Aquarius, about five degrees north of the star Sadalsuud (β Aquarii), which makes it relatively easy to find during autumn observing sessions.
Messier 2 stands out both in scale and antiquity. It lies about 55,000 light-years from Earth, and its diameter is estimated at roughly 175 light-years, a size that places it within the Milky Way’s largest globular clusters. With an age of roughly 12.5 billion years, it belongs to the Galaxy’s oldest surviving stellar populations. The cluster contains close to 150,000 stars, dominated by red and yellow giants, along with at least 21 known variable stars.
Recent studies indicate that M2 is part of a structure known as Gaia Enceladus, also referred to as the Gaia Sausage. This extensive stellar stream is thought to be the remnant of an ancient dwarf galaxy that merged with the Milky Way billions of years ago. If so, many of M2’s stars may have originated in that long-lost system, which once existed as a galaxy in its own right.
Photo 1 Parameters:
- total exposure time: 30 minutes (stack of 60 RAW frames at 30s each, using an appropriate number of dark, bias, and flat frames)
- ISO: 1600
- Maksutov-Cassegrain telescope (100/1400), prime focus exposure
- A filter was used to reduce the effects of artificial light pollution and atmospheric glow
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system.
Further readings:
- Shapley H., Sawyer H. B., A Classification of Globular Clusters, Harvard College Observatory Bulletin, 849 (849), 1927, pp. 11-14.
- Goldsbury R., Richer H. B., Anderson J., Dotter A., Sarajedini A., Woodley K., The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters, The Astronomical Journal, 140 (6), 2010, pp. 1830-1837.
- Boyles J., Lorimer D. R., Turk P. J., Mnatsakanov R., Lynch R. S., Ransom S. M., Freire P. C., Belczynski K., Young Radio Pulsars in Galactic Globular Clusters, The Astrophysical Journal, 742 (1), 2011, art. 51.
Marek Ples