Collinder 69 Open Cluster & Meissa (Lambda Orionis)
Probing Orion’s Brain
Long before the invention of the telescope, it was noted that Orion’s head was marked by a
misty patch. As a kid growing up in Oregon, I dubbed it Orion’s Brain. The misty nebula
easily resolved into stars with my 2.4” refractor, but at the time none of the astronomy books
I owned gave it a name. It was many years later that I found out that my “Orion’s Brain” was
an open cluster called Collinder 69 and that the fuzziness was the result of its 20 stars being
so close together in the night sky that when view with the unaided eye they appear as a misty
blur. Collinder 69 is a stunning star-studded sight in binoculars and rich field telescopes.
At the center of the cluster, and easily seen without any optical assistance, even from my
light polluted skies in suburban Maryland is the star Meissa (Arabic for “The Shining One”).
Meissa goes by the more modern designation of Lambda Orionis and is one truly
impressive star. Meissa has 28-times the mass of our sun and is 10-times the sun’s radius. It
is so massive that its lifetime will be measured in millions of years and not billions like our sun.
When it dies, its core will disappear from our Universe into a stellar black hole. The intense
ultraviolet energy being radiated by Meissa is making the surrounding hydrogen gas region
(designated Sh2-264) to glow. Unfortunately, the glow is subtle, and I have never been able
to make it out through the telescope. In addition, there is another outer ring of cooling gas
surrounding Sh2-264. The origin of this outer ring (also not visible to me through the
telescope) is likely due to a former binary companion star of Meissa that went supernova
between 2 and 6 million years ago. One last thing, when you take the time to look into
Orion’s Brain, spend a few seconds and up the magnification on Meissa. It is a fine double star
in a small telescope.