M35 - Open Cluster in Gemini


At distance of 2,800 light years, M 35 has a linear diameter of about 24 light years; its central density is about 6.21 stars per cubic parsec. The mass within the central 3.75 parsecs of M 3 5has been computed at 1600 to 3200 Suns. M 35 is of intermediate age, about 100 million years old, and contains some post-main-sequence yellow and orange giants of spectral type G and K. Its hottest main sequence star is of spectral class B3. M 35 is approaching us at 5 km/sec.

The much smaller open cluster NGC 2158 lies 26' away, toward the south west. It is smaller (5' in diameter) and fainter (magnitude 8.6) because it is much further away - 16,500 light years as opposed to 2,800 for M 35. It is over ten times older than M 35, and because of this, its light is dominated by yellower stars; the hottest is of spectral type F0.

About 50' to the west of M35, the faint open cluster IC 2157 can be found. With a total visual magnitude of 8.4 and an apparent diameter of 8', it is similar to NGC 2158, but contains many fewer stars. IC 2157 is a loose and poor cluster, containing some very hot young OB stars;


Technical Data

Bortle Scale / SQM-L Bortle 4/5  / ---
Period January 2016
Primary Scope  FSQ 106/530
Camera CCD  KAF-8300
Mount NEQ6
Total Exposure Time 2h
Composition RGB
Location Val Imagna (Bergamo) Italy


 © Efrem Frigeni Astrophoto

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