Globular Clusters and the Early Universe

The origins of our universe began as a blank canvas, an expanding landscape of endless hot clouds of hydrogen and helium. For the first few hundred million years the universe was nearly featureless and chemically pristine, void of any heavy elements or complexity. It was a simple and humble beginning onto which the cosmos would mold all subsequent structure and complexity over the course of billions of years eventually leading to rich planetary systems and eventually life here on Earth. Yet lurking within the outer halo of our own galaxy exist isolated clumps of ancient stars that still preserve the pure conditions of this earlier period.

The Early Universe

During the very early universe, it was too hot to easily form stars. Only the most densely packed, massive regions of space were capable of collapsing and condense from the hot gas to form the initial stars. These first stars were extremely massive, on the order of 100x the mass of the Sun and had incredibly short life spans as they popped in and out of existence for just a cosmic blink of an eye. Living for just a short few million years of existence, each star was extinguished one after another in violent supernova events like firecrackers popping off in rapid succession. These fiery explosions forged the first heavy elements to ever exist in the universe.

Gas will naturally cool as the materials within radiate energy, however heavier elements like carbon and oxygen will accelerate this cooling effect far more efficiently than hydrogen and helium can. So this initial production of the first heavy elements was a crucial first step which allowed the interstellar medium to cool enough to form the first smaller stars. And unlike very massive stars, small stars are much more stable and live very long lifespans, some of which are still around and visible today.

Astronomers can actually measure the chemical abundance of each element for a given star providing clues as to when the star formed. Within our own Sun, scientists measure quantities of oxygen, carbon, nitrogen, silicon and many other elements which were forged by generations of past ancestors. Surrounding the outer halo of the Milky Way however, exist around 150 known star clusters known as globular clusters. When we closely examine these isolated and tightly packed clumps of stars, we observe only miniscule traces of heavy elements, leading astronomers concluding that these are among the oldest surviving stars in the universe.

M13 – The Hercules Globular Cluster

Within the constellation of Hercules at just 22,000 lightyears away, hovering just above the galactic plane, lies one of the most famous and well-studied globular clusters. M13 also known simply as the Hercules Globular Cluster, is a dense ball of a few hundred thousand small stars that are an estimated 11.7 billion years old. Its long lived isolation preserved the chemical environment of the early universe much like layers of deep sedimentary rock preserve the conditions of Earth?s past. Over time, gravity will no doubt cause our galaxy to consume these ancient relics, continuing the gradual and ongoing galactic assembly process that has created our home, the Milky Way galaxy.

The Hercules Globular Cluster is viewable in the evening skies from mid-March to late-September. So be sure to book a personal stargazing tour with Wyoming Stargazing right here in Jackson, WY to see it for yourself!

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