Astronomers Discover The Oldest Known Star In The Universe

NASA/WMAP Science Team

A few hundred thousand years after the Big Bang, hydrogen gas started to heat up and the first stars were formed. One of these first stars, which formed around 13.7 billion years ago, has been discovered for the first time. The discovery was made by lead researcher Stefan Keller of The Australian National University and the results were published in Nature.

Dr. Keller’s team is one that operates the SkyMapper telescope at the Siding Spring Observatory in New South Wales. Because elements heavier than helium are forged in the cores of stars, the first ones were made mostly out of hydrogen. The telescope is able to find these first stars because the low iron content influences their color. Using this technique to find early stars, the SkyMapper is currently in a 5-year-long survey, mapping the ancient Southern sky.

The team made the discovery of a lifetime when they discovered the chemical signature from a 13.7 billion year old star; one of the first ever. This star formed so early in our Universe’s history, was most likely a second-generation star. Because of the chemical composition, astronomers can gather information about the earlier primordial star, which is believed to be 60 times more massive than our sun and composed of hydrogen and helium.

The stars we are most familiar with today have different stages in their life cycle. For massive stars (those which are over nine solar masses) heavy elements are fused in the core of the star, up until it hits iron. The nuclei are so tightly bound that it actually consumes energy, instead of producing it like other elements. As more and more iron is created, the star’s core becomes so massive that it eventually collapses, signifying the death of the star. The supernova explosion is violent and all of the elements are ejected out where they will eventually form new stars or planetary bodies. 

It had long been assumed that the first stars exploded in similar ways, but the team found that this wasn’t the case. The explosion from the primordial star’s death was relatively low-energy. While the lighter elements were ejected and would go into new stars, the heavier elements, like the iron, were consumed by the black hole that formed after the supernova. The newly-discovered second-generation star did not have the iron that astronomers believed they would have.

The discovery of this ancient star has given astronomers a deeper insight about the origins of stars and how certain elements began to spread around the early Universe. These low-energy supernovae were likely very common among the first stars and future research will determine when they began to gather more energy and become the explosive events we know them to be today. 

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