Let’s continue this site’s survey of Messier objects. Check some basic info if you’re joining us in mid-star-stream. Today, a return to the Scorpio constellation where we encountered M4. Unlike the globular clusters M2, 3, 4, and 5, the Butterfly is an open cluster. What’s the distinction? Check it out:
Image credit: By Ole Nielsen – http://www.ngc7000.org/ccd/m6-20050902-900.jpg, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1189995
Globular clusters, as the name suggests, are rather compact and mostly spherical in shape. Open clusters are more diffuse and often more varied in shape. It is thought the stars formed together in an interstellar cloud, but as the eons pass, they are tugged apart because they haven’t been quite as close in the early millions of years as a grouping. Think of them as a teenage clique that gradually breaks apart as members go off to different colleges or work experiences.
The individual stars here are a bit less than 100 million years old. Infants, compared to middle-aged celestial bodies like the sun.