The Hubble Space Telescope has set another record by recording the most distant star ever seen. It belongs to a galaxy whose light left there just 900 million years after the Big Bang, the event that gave rise to the Universe as we know it today.
Under normal circumstances, it is impossible to observe individual stars even in the closest galaxies. The result was only possible because of an effect predicted by Albert Einstein’s general relativity, gravitational lensing.
The German physicist concluded that high-mass objects that come between us and more distant objects can deflect light rays by gravity, effectively acting as an immense lens in space, capable of distorting and amplifying light on its way to us.
This galaxy is located “behind” a huge galactic cluster cataloged as WHL0137-08. It was noted to appear as a large arc — one of several studied by Relics (acronym for Reionization Cluster Lensing Research), a program that used Hubble Space Telescope images to study 41 galactic clusters that produce gravitational lensing.
The new finding identified that at the most intense point of the lens, where there was greater magnification, was located a star of this background galaxy, now designated WHL0137-LS, a star that researchers led by Brian Welch, from Johns Hopkins University, in the USA, dubbed from Earendel, an Old English word meaning “morning star” or “rising light”. Later images of the same object showed that this magnification persisted for 3.5 years.
The phenomenon made the star more than a thousand times brighter than it actually is, which allowed an initial study of it. Astronomers do not yet know whether Earendel is a solitary or binary star, but they have estimated its mass to be more than 50 times that of the Sun. It is a colossal size, even for high-mass stars, which indicates that we may be facing an example that refers much more to the first stars to form in the Universe (which, according to the models, should be much larger) than to the equivalent ones. modern.
It was also possible to determine that it is the most distant star, therefore, the oldest, ever observed. After all, the further an object is, the longer it takes its light to reach us. In the case at hand, the light traveled for 12.9 billion years before being detected by Hubble, which puts the image as a faithful portrait of a star born and created just 900 million years after the Big Bang (it is estimated the Universe is 13.8 billion years old).
The new find beat the previous record, from 2018 and also from Hubble, by a wide margin. Before Earendel, the oldest star ever observed dated to the time when the cosmos was 4 billion years old.
The best news, however, is the longevity of the lensing, which has lasted for at least 3.5 years and should last a little longer, in time for the recently launched James Webb Space Telescope, about to go into operation, to be able to observe -there. In their paper published in the journal Nature, Welch and his colleagues point out that, with the new observatory, it will be possible to confirm Hubble’s detection and even study the star’s composition and spectral type. They end, by the way, by pointing out that these observations will be made soon, as the request for the use of Webb for this purpose has already been approved.
“Earendel existed so long ago that it may not have had all the same raw material that the stars around us have today,” says Welch. “Studying it will be a window into an era of the Universe that we are not familiar with, but has led to everything we know. It is as if we were reading a very interesting book, but we started with the second chapter, and now we will have the chance to read like everything else. started.”
In other words, the best thing about Earendel is yet to come. And we can bet that Webb has what it takes to beat this record and find even more distant and primitive stars in the near future.
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