The most distant oxygen detected shows the traces of the formation of the first stars

The galaxy cluster MACS J1149.5+2223 and in the inset the galaxy MACS1149-JD1
The galaxy cluster MACS J1149.5+2223 and in the inset the galaxy MACS1149-JD1

An article published in the journal “Nature” describes the discovery of the most distant traces of oxygen ever detected. A team of astronomers used the ALMA radio telescope and ESO’s VLT telescope to observe the galaxy MACS1149-JD1, where there are traces of star formation about 250 million years after the Big Bang, a very remote era in which so far there were just some clues of possible star formation.

The timeline of the evolution of the universe in the early stages of its life is the subject of discussion because of the difficulty in obtaining certain and precise data. Among the problems there’s the birth of the first stars and the research is pushing the current instruments to their limits to investigate that subject.

In March 2018 an article published in the journal “Nature” describes a research that described the detection of possible traces of the first stars born in the universe, found in cosmic microwave radiation from the hydrogen that existed at that time. The analysis of that trace indicates that the stars that generated it existed about 180 million years after the Big Bang.

Now a new research reports traces of early stars through their products, especially oxygen. In this case, the astronomers used the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope, inaugurated in March 2013, and ESO’s VLT (Very Large Telescope) to study the galaxy cluster MACS J1149.5+2223 and in particular the galaxy MACS1149-JD1 within it.

The image (ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, W. Zheng (JHU), M. Postman (STScI), the CLASH Team, Hashimoto et al.) shows the galactic cluster MACS J1149.5+2223 seen by the Hubble Space Telescope and in the inset the galaxy MACS1149-JD1 seen by the ALMA radio telescope.

ALMA allowed to detect the “signature” of oxygen in the electromagnetic emissions of the galaxy MACS1149-JD1 while VLT allowed to detect a weaker “signature” of hydrogen. The observations made it possible to estimate the distance of the galaxy in about 13.3 billion light years, which means that it existed 500 million years after the Big Bang.

In that early universe the galaxy MACS1149-JD1 shows that it already has a population of stars and the presence of oxygen indicates that a generation of massive stars had already exploded into supernovae generating that type of elements. The stronomers also used infrared observations made with the Hubble and Spitzer space telescopes, discovering that the observed brightness is well explained by a model that sees the start of star formation 250 million years after the Big Bang.

This is another indirect indication of the birth of the first stars, obtained thanks to traces produced by them and not to direct observations. Takuya Hashimoto, the lead author of the article, pointed out that this research pushes the frontiers of the observable universe further back. It’s a result obtained thanks to the combination of the use of different instruments.

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