Researchers from Johns Hopkins University and the team from the Space Telescope Science Institute have discovered, thanks to the hubble telescopewing most distant and oldest star ever observed. Nicknamed Eärendel, it is a star 12.9 billion light-years from Earth that formed when the universe was still young, so it will be a gate to understand stellar evolution.
Although this star exploded millions of years ago, its light was so powerful that it is still possible to visualize it. This discovery, the researchers pointed out, represents a new record, since so far the most distant star detected was Icarus, observed in 2018 at 9,000 million light years away.
The discovery published this Wednesday by “Nature” was made by an international team led by Brian Welch of Johns Hopkins University (USA) and the team from the Space Telescope Science Institute.
“So far we’ve only seen recent stars, never one as old as this.that existed in the first billion years after the Big Bang)”, José María Diego, of the Institute of Physics of Cantabria (IFCA, CSIC-UC), in northern Spain, recognized the signatories of the ‘study.
This finding, said the expert, will be essential to understanding how stars formed and how they evolvedas well as to understand the reionization stage of the universe, a period during which free electrons circulated and which remains a mystery for specialists.
The observed star will be “a window into an epoch in the universe that we don’t know, but which led to everything we know. It’s as if we read an interesting book, but we start at the second chapter and now we have the opportunity to see how it all began“said, for his part, Brian Welch.
Eärendel and the origin of its name
The star is located in the Sunrise Arc galaxy and takes its name from the poem “The Voyage of Eärendel, the Evening Star”written in 1914 by JRR Tolkien, author of “The Lord of the Rings”.
According to the researchers in charge of the discovery, it would have, at least, 50 times the mass of the Sun and is much brighter than that. To accurately determine its mass, size, temperature and radius and to be able to establish whether it is a first or second generation star, it will be necessary to wait until the recently launched James Webb Telescope is fully operational.
The difference between the first and second generation stars is that the first, closer to the beginning of the Big Bang, were only composed of hydrogen and helium, because with a little lithium, they were the only elements of the universe. In contrast, the second generation contains small amounts of other elements.
Currently, from Eärendel there is only his light. To predict if its brightness will last for years or if it is temporary “you have to estimate the mass of all the stars that are in the line of sight”explained Yolanda Jiménez, of the Institute of Astrophysics of Andalusia (IAA-CSIC), in southern Spain, who also participated in the project.
Combination between Hubble and gravitational lens
Eärendel’s discovery was made possible by a combination of Hubble, the telescope that has provided countless scientific insights for almost 32 years, and a natural phenomenon called gravitational lensing.
A gravitational lens is a very high concentration of matterin this case a cluster of galaxies so massive that curve the space around it. As it passes through this area, the light bends and acts as a lens.
Looking through this gravitational lens, Hubble amplifies what it sees behind and, in very small areas, this expansion can be “very very high”. Eärendel is right in one of those areas, Diego points out.
It’s “something nature gives us”, a phenomenon called gravitational lensing, the effect of which is like making Hubble 70 times bigger. “There is no telescope on Earth that is this big; It’s a unique combination.” celebrates the scientist.
At the moment, Eärendel only looks like a three-pixel dot. However, “the amount of information that can be obtained from a single point is incredible”, stressed the expert.