|Magnitude: +6.9||Diameter: 19 light years.|
|Apparent size: 25 arc min||Distance: 2600 light years.|
Open star clusters are groups of stars which have formed from collapsed molecular hydrogen clouds. Over a thousand of such clusters, of varying sizes, have been identified in the Milky Way galaxy. Open clusters contain stars, of a similar age and composition, which are only very loosely bound together by gravity and consequently most clusters get pulled apart and eventually disperse within a few million years of formation, with each (still young) star wandering off in different directions into the galaxy, to follow its own path.
The Mystery of M67
Contrary to this norm, the M67 cluster contains many stars that are in the latter stages of life, having already evolved into red giant stars. It is among the oldest of open clusters – estimated at about four billion years!
How can this be? Why didn’t M67 break up at an early age, like most open clusters are supposed to do?
The answer seems to be that M67 wandered quickly away from the the strong tidal forces of the galactic plane. It may possibly also have been helped by a stronger mutual gravitational attraction within the cluster itself, due to many of its component stars being quite massive.
|Feature image date:||2021-04-03|
|Exposure:||236 sec x 16 = 63 minutes|
|Field of View:||1.59° x 1.06 ° (Orientation: up is 49.9° E of N).|
Where Is It?
Location of M67
If the Astrometry images do not appear it is because the Astrometry website is sometimes off line.
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.|
|Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.|
|SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.|
|Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).|
|Software: Telescope control: Cartes du Ciel, EQMOD, PHD2, Imaging: SharpCap, Gimp.|
|Observatory location: 34° South.|
Images © Roger Powell
I’m webmaster and a founder member of Macarthur Astronomical Society