Globular clusters

Sinai stars

An artist’s view of a globular cluster viewed from a nearby rocky planet

In 1974, a radio message, written by Carl Sagan, was sent to the Globular cluster, M13, in the constellation of Hercules. Since the cluster is 25,000 light years away, a reply by return of post cannot be expected for another 50,000 years. If it wasn’t a joke, it was a quaint dream of chatting with extra-terrestrials.

M13 was chosen because it represents the greatest concentration of stars within our immediate reach, hundreds of thousands. Surely some of them would have planetary systems? The cluster was also old, over 13 billion years old, plenty of time to give life a chance to evolve, after all, intelligent life on our planet took 5 billion years to develop.

But therein lies the problem. Globular clusters are so old, formed so soon after the Big Bang that only hydrogen and helium would have been present, the only elements that were produced in the Big Bang. There just wouldn’t have been the material for planets and protoplasm in the early universe. Heavier elements, so necessary to form gritty planets and living organisms were only created much later when the larger stars died out in colossal supernovae explosions, forging the heavier elements in the terrible furnace of their extinction.

A close study of globular clusters reveals that the all their large stars have gone supernova and vanished, leaving only medium and small stars. The heavy elements that would have been produced, however, are not concentrated enough to form new stars around which living planets might form. It required the formation of galaxies to create those conditions in which billions of stars recycle enough gas to produce younger second generation stars with planetary systems.

Our galaxy is surrounded by a halo of globular clusters, mute testimony to the early universe. It was from these isolated star groupings that galaxies first formed which then allowed life to emerge.

This story first appeared in the Cairo BCA magazine of June 2011 to encourage visitors to come to Sinai for star gazing with an 8″ Meade telescope.

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