M56 - Globular Cluster in Lyra
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Messier 56, also known as NGC 6779, is a globular cluster located in the constellation Lyra. It was discovered by Charles Messier in 1779. The object is situated on the celestial sphere almost exactly halfway between the stars Albireo β Cygni and Sulafat γ Lyrae. Globular clusters like M56 are among the oldest structures in the Milky Way, with M56's age estimated at about 13.7 billion years. It is approximately 32.9 thousand light-years from Earth, nearly 1.5 kiloparsecs above the Galactic plane, and is on a retrograde orbit, suggesting its extragalactic origin. Evidence suggests it was formed when the Milky Way merged with a dwarf galaxy a long time ago. The Omega Centauri cluster could be another leftover from that cosmic event.
Observations
August 08, 2025, about 10:00 p.m. - Jaworzno, Poland
urban conditions, high level of light pollution
M56 extends for about 84 light-years and has a mass equivalent to approximately 230 thousand solar masses. Its stars are characterized by extremely low metallicity, meaning the abundance of elements heavier than helium is many times lower than in the Sun. The brightest components of the cluster have a magnitude of 13m, which makes it visible in 50 to 80 mm binoculars as only a slightly blurred, small star. Telescopes with an aperture of at least 20 cm (7.9 inches) are required to visually resolve individual stars. As always, long-exposure astrophotography helps to observe the details (Photo 1).
Just over ten variable stars have been identified in the cluster, including V6 (an RV Tauri-type with a 90-day period) and V1 (a Cepheid with a 1.51-day period). In 2000, diffuse X-ray emission was also observed in its vicinity, most likely caused by the heating of the interstellar medium as the cluster moves through the Galactic halo at a velocity of approximately 177 km/s (110 miles/s).
Photo 1 Parameters:
- Total exposure time: 25 minutes (stack of 25 RAW frames at 60s 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, 1927, 849 (849). str. 11-14
- Bica E., et al., Globular cluster system and Milky Way properties revisited, Astronomy and Astrophysics, 2006, 450 (1). str. 105-115
- Boyles J., et al., Young Radio Pulsars in Galactic Globular Clusters, The Astrophysical Journal, 2011, 742 (1), str. 51
Marek Ples