M39 - Open Cluster in Cygnus
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Messier 39 is an open star cluster located in the constellation Cygnus (The Swan). There is evidence suggesting that this object was known in antiquity; its observation is attributed to Aristotle around 325 BCE. Modern observations began with Charles Messier, who officially added it to his catalog on October 24, 1764.
The cluster lies at a distance of approximately 825 light-years from Earth, which corresponds to roughly 253 parsecs. It is moving toward the Solar System at a radial velocity of 28 km/s (17.4 mi/s). Its estimated diameter is about 7 light-years, and its apparent magnitude is 4.6m. According to the latest estimates, the cluster is between 230 and 300 million years old.
Observations
May 1, 2025, around 11:00 PM – Katowice (Poland)
very high level of light pollution
Like other objects in the Messier catalog, this star cluster is accessible to amateur astronomers — under dark skies, it may even be visible to the naked eye. However, under most conditions, a small pair of binoculars or a low-aperture telescope is needed to observe it. To locate M39 in the night sky, first find Deneb, the brightest star in Cygnus, then move about 9° eastward to the star ρ Cygni (4m). The cluster lies 3° north and roughly 0.25° west of ρ Cygni.
The cluster contains between 50 and 100 identified stars. The brightest among them reaches an apparent magnitude of 6.83 and is classified as spectral type A0, indicating the presence of hot, main sequence stars.
Photo 1 Parameters:
- ZWO Seestar s50
- Total exposure time: 15 minutes (stack of 90 RAW frames at 10s each, stacked by Siril ver. 1.2.3)
- A filter was used to reduce the effects of artificial light pollution and atmospheric glow
Further readings:
- Wu Z. Y., et al., The orbits of open clusters in the Galaxy, Monthly Notices of the Royal Astronomical Society, 2009, 399(4), pp. 2146-2164
- Kharchenko N. V., et al., Astrophysical parameters of Galactic open clusters, Astronomy and Astrophysics, 2005, 438(3), pp. 1163-1173
- Schuff S., et al., A Search for Variable Stars in the Field of NGC 7092 (M39), Bulletin of the American Astronomical Society, 2006, 38, p. 1135
Marek Ples