Ever think about how a star is born? An entertainer’s birth is their discovery, a star is born. How things go from there depends on many factors.
A celestial star’s birth is more predictable, determined by the conditions within a molecular hydrogen cloud. Hydrogen is the primary element, the simplest element, the first element to exist, and the most abundant element in our universe. Good thing for us because hydrogen is the stuff of stars. If hydrogen hadn’t been born of the big bang, well, our universe might have just fizzled, like a dud firework. Would stars even exist? I don’t know but this universe would be a very different place.
Hydrogen, lots of hydrogen came from the big bang. After big bang plasma cooled enough , atoms of hydrogen formed, went forth and gathered into vast, dense molecular clouds. Those clouds started rotating and areas of higher density started rotating faster. Even clouds have gravity – because every atom of hydrogen within the cloud has gravity. Gravity curves spacetime, so atoms and molecules eventually move in a rotation that concentrates into a dense mass.
At some point the first star flashes, but not yet visible as it’s still wrapped in a molecular hydrogen blanket. Its first light is shaded, for now.
This is constantly happening within the molecular cloud and in molecular clouds throughout the universe, stars flashing to life inside their hydrogen cocoons. Most are cohorts, they are gravitationally bound to other stars in groups of tens to thousands. They will eventually cast off their molecular veil to reveal clusters of brilliant stars, many so massive they will live only millions of years while furiously fusing their life giving hydrogen.
Most stars aren’t born alone. Most stars are born in a litter. About 5 billion years ago our Sun was in a litter of stars we now call an open star cluster. The thing about open clusters, they are not strongly tied by gravity and drift apart over time. Our Sun had cohorts, but where are they?
Open star clusters are new generation stars and at least some of the stars are mellow like our Sun, maybe with solar systems. In a few billion years they will have drifted apart too.
Open star clusters are called ‘galactic star clusters – they reside within the galaxy. The other type of star cluster is called a globular star cluster – they reside just outside and orbit our galaxy. Open star cluster stars are young (millions of years old) and globular star cluster stars are old (billions of years old). We know how open star clusters form, but globular star cluster formation is still an enigma and under study.
What’s in the Sky?
Late winter is a good time to observe open star clusters. Look them up and check them out with binoculars. Here are some: M44, M57, M46, M47, M41, M35, M36, M37, M38, The Hyades, The Pleiades (M45), The Double Cluster, M52.
February 14; an hour after sunset; west: Jupiter and Venus grace the western sky. Neptune is in conjunction with Venus – use binoculars.