NGC 6939 is an open star cluster situated in the northern constellation of Cepheus. This celestial grouping is characterized by a rich concentration of stars, creating a visually appealing stellar arrangement. Located in the Milky Way, NGC 6939 offers astronomers valuable insights into the formation and dynamics of open clusters within our galaxy.
Location and neighborhood.
Its celestial coordinates are approximately right ascension 20h 34m 05s and declination +60° 06′ 45″ (J2000 epoch). Observers in the northern hemisphere can spot Cepheus during different seasons, and NGC 6939’s position within this constellation makes it visible in that specific region of the night sky.
- The cluster is estimated to be around 1.6 billion years old, making it relatively young in astronomical terms. Additionally, it is situated at a distance of approximately 4,000 to 5,000 light-years from Earth.
Brightness and size
NGC 6939 has an apparent visual magnitude of about 7.8. This makes it visible to observers with binoculars or small telescopes under relatively dark skies. The apparent brightness is a measure of how bright the cluster appears from Earth.
The physical size of NGC 6939 is approximately 12 arc minutes. This angular measurement represents the apparent size of the cluster in the sky. To put it in perspective, the full moon has an angular size of about 30 arc minutes, so NGC 6939 appears much smaller but is still discernible with optical instruments.
The cluster’s angular size on the sky is around 12 arc minutes, providing observers with a moderately compact appearance. This makes NGC 6939 suitable for observation with amateur telescopes, as it covers a noticeable portion of the celestial sphere.