NGC 2158 is a globular star cluster located in the constellation Gemini, situated relatively close to the more prominent open cluster Messier 35.
This globular cluster is significantly older than Messier 35, with an estimated age of around 10 billion years, and it contains a much denser concentration of stars.
NGC 2158 exhibits a more spherical and tightly packed structure compared to Messier 35, and its stars are predominantly older, low-mass stars, creating a distinct stellar population within the Gemini constellation.
Observationally, NGC 2158 appears as a fainter and smaller celestial object than Messier 35, requiring a telescope for detailed viewing due to its greater distance and less apparent brightness.
Location and neighborhood.
NGC 2158 is located in the constellation Gemini. To find it in the night sky, you can look toward the winter sky in the Northern Hemisphere or the summer sky in the Southern Hemisphere, as Gemini is visible during both seasons. Specifically, NGC 2158 is situated to the northeast of the more prominent open star cluster Messier 35 in Gemini. While Messier 35 is visible to the naked eye or with binoculars, NGC 2158 is fainter and may require a telescope for observation due to its greater distance and less apparent brightness.
Unique facts
- NGC 2158 is a globular cluster, a spherical collection of stars bound together by gravity. Unlike open clusters, globular clusters are densely packed and contain much older stars.
- NGC 2158 is significantly older than the nearby open cluster Messier 35, with an estimated age of around 10 billion years. This age difference highlights the distinct evolutionary paths of these two stellar groupings within the Gemini constellation.
- NGC 2158 has a dense central core, with stars packed closely together. The high density of stars within globular clusters contributes to their spherical appearance and distinguishes them from the more dispersed structure of open clusters.
- While Messier 35 is visible to the naked eye or with binoculars, NGC 2158 is fainter and requires a telescope for detailed observation. Its greater distance and less apparent brightness make it a challenging but interesting target for amateur astronomers equipped with suitable telescopic instruments.
Brightness and size
NGC 2158 has an apparent magnitude of approximately 8.6. This makes it fainter and less luminous than Messier 35, the nearby open cluster in the Gemini constellation.
NGC 2158 is located at a greater distance compared to Messier 35. It is estimated to be around 13,000 light-years away from Earth. This substantial distance contributes to its fainter appearance in the night sky.
NGC 2158 has a physical diameter of about 10 to 12 light-years. This measurement represents the extent of the cluster in three-dimensional space, encompassing the region where its stars are distributed.
The apparent size of NGC 2158 in the night sky, measured in arcseconds, depends on the field of view of the observing instrument. Given its relatively small size and fainter appearance, NGC 2158 might require a telescope for detailed observation, and the specific angular size would vary based on the telescope used.
