Earliest stars in our Universe formed 250 million years after Big Bang

by Khadija Khurram
2 minutes read

Scientists have determined through analysis of observations made by the Atacama Large Millimeter/ submillimeter Array (ALMA) that the first stars in our Universe could have forged just 250 million years after the Big Bang.

The findings are based on faint, telltale signature of oxygen coming from the galaxy, which is thought to have been formed just 500 million years after the Big Bang. Scientists say that for galaxy MACS1149-JD1 to show traces of Oxygen at such a young age indicate that its constituent starts could have started forming just 250 million years after the Big Bang.

This is exceptionally early in the history of the universe and suggests that rich chemical environments evolved quickly, according to the study published in the journal Nature.

Scientists believe that after the Big Bang our Universe wasn’t diverse chemically and there wasn’t even a trace of elements like oxygen during the early years of our Universe. It would take several generations of star birth and supernovas to seed the young cosmos with detectable amounts of oxygen, carbon, and other elements forged in the hearts of stars. After they were liberated from their stellar furnaces by supernovas, these oxygen atoms made their way into interstellar space. There they became superheated and were ionized by the light and radiation from massive stars. These hot, ionized atoms then ‘glowed’ brightly in infrared light. As this light travelled the vast cosmic distances to Earth, it became stretched by the expansion of the universe, eventually changing into the distinct millimeter-wavelength light that ALMA is specifically designed to detect and study.

By measuring the precise change in the wavelength of this light – from infrared to millimeter – the team determined that this telltale signal of oxygen traveled 13.28 billion light-years to reach us, making it the most distant signature of oxygen ever detected by any telescope. This distance estimate was further confirmed by observations of neutral hydrogen in the galaxy by the European Southern Observatory’s Very Large Telescope.

These observations independently verify that MACS1149-JD1 is the most distant galaxy with a precise distance measurement. The team then reconstructed the star formation history in the galaxy using infrared data taken with the Hubble Space Telescope and NASA’s Spitzer Space Telescope.

The observed brightness of the galaxy is well explained by a model where the onset of star formation was another 250 million years ago. The model indicates that the star formation became inactive after the first stars ignited. It was then revived at the epoch of the ALMA observations: 500 million years after the Big Bang.

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