M35

Alternate: NGC 2168

Gemini

RA 06h 09.1 m

Dec +24º21′

Magnitude 5.3

NGC 2158

Alternate: none

Gemini

RA 06h 07 m 25 s

Dec +24º05.8′

Magnitude 8.6

 

M35 is the only Messier open cluster in Gemini. It was discovered byJean-Philippe Loys de Chéseaux in 1745 and independently discovered by John Bevis before 1750. This star cluster is large and covers an area the approximate size of thefull Moon. M35 is located 2,200 light-years from Earth. M35’s Trumpler classification as III,3,r according to all reference sources.

With an age of approximately 100 million years, M35 is an intermediate age open cluster, and contains several yellow and orange giants of spectral type late G to early K. Its hottest main sequence star is given as of spectral class B3. With a blue Doppler shift, it is approaching Earth at a rate of 5 km/sec.

The compact open cluster NGC 2158 is directly southwest of M35. NGC 2158 is also an open cluster in Gemini.

The two clusters are unrelated, as NGC 2158 is around 9,000light years further away than M35.

Observing this Cosmic Duet definitely benefits from a dark and moonless night, where M35 is easily seen, but the dimmer NGC 2158 appears as a faint smudge. Although within reach and observable through my 4” apochromat refractor, the dimmer NGC 2158 was more apparent and observable in the my 130 mm apochromat refractor and my 9.25” SCT.