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[EN VIDÉO] Understand the James Webb Space Telescope mission in one minute The James Webb Space Telescope, a new flagship in space observation, will be launched on December 18 from Kourou, Guyana. After a journey of 29 days, it will reach the Lagrange point L2, in the opposite direction to the Sun. With its mirror larger than that of Hubble, of which it is considered the successor, the JWST will be able to observe galaxies, planets, nebulae and stars to learn more about the history of the Universe.
We have undoubtedly entered the era of the James-Webb Space Telescope (JWST) and it promises to be even brighter than that opened thirty years ago with the Hubble telescope.. In particular, we expect the JWST to shed some light on what happened shortly after the end of the dark ages followed by the “cosmic rebirth”, also called theDawn cosmic, which is the epoch of re-ionization (EoR), when powerful light sources – whose origin is not yet known with certainty – began to significantly re-ionize the atoms neutrals that had formed in a few thousand years, about 380,000 years after the big Bang.
Astronomer Michelle Thaller explains to us in this video what the Cosmic Dawn is, a period of re-ionization, which will make it possible to study the James-Webb and not just him. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Nasa Goddard Space Flight Center
The precise date of the beginning of the re-ionization is subject to debate, and all that can be said is that it occurred between 100 and 400 million years after the big Bang. Before, at the very beginning, no star existed yet, but during the EoR there is reason to think that those which formed and shone were very massive, at least 50 to 100 million masses solar. We are talking about these stars in terms of stars of people IIIjust like a 3 month old baby is older than a 1 month old baby.
A nearly population III star?
The evolutionary theory stellar tells us that these stars lived a million years at the most, producing by nucleosynthesis stellar for the first time in theUniverse observable nuclei heavier than the lithiumwhich they will then disperse in the young cosmos by exploding as a supernova. In doing so, they will modify the composition of the clouds where new stars can be born by collapse gravity, subsequently favoring the appearance of less massive stars, so that more than a billion years after the Big Bang, it has become impossible to observe stars with all the characteristics of those of population III.
Astronomer Michelle Thaller’s explanations of population III stars and Earendel. © Space.com
However, it is possible that the star at the record distance discovered recently with the hubble telescope and which Futura had discussed in some detail in the previous article below, Earendel, either one of the last population III stars born less than a billion years after the Big Bang (or at least very similar to them), or much more likely, as explained by theastronomer Michelle Thaller, alas in English in the video above, an example of stars with very little difference in composition and properties, born just after them.
Remember that she was only flushed out with the help of a gravitational lensi.e. the magnification effect (in this case by a factor of at least 1,000) caused by the gravitational field of a cluster of galaxies intervening between Earendel and Hubble, deflecting light rays like a magnifying glass.
Calculations then indicated that Earendel must contain at least 50 solar masses and that it was observed when the Universe was only about 900 million years old.
Recently, the first image showing Earendel was posted on Twitter.
Hubble breaks all records for the most distant star ever observed
Article of Laurent Sacco published on 03/04/2022
the Hubble Space Telescope has just shown that we could always count on him to set a distance record for stars in the distant Universe, before the commissioning of the James-Webb telescope. The Nasa has just announced that he had imaged the most distant star known to date, as it was 12.9 billion years ago.
Her name is Earendel and one would think that it is a variation of the name ofEarendilone of the elvish characters created by the British writer JRR Tolkien and which is mentioned in The Lord of the Rings. NASA explains, however, that it is an old English term meaning ” morning Star “. But, for us, it is above all a star observed when the Universe was only 7% of its age, which means that the photons which were collected with the Hubble telescope took 12.9 billion years to reach it.
The most distant star known to date
It is in fact the most distant star ever discovered to date and like some of the distant galaxies which, in their time, broke distance records thanks to the Hubble telescope, the astrophysicists took advantage of the gravitational lensing effect of a significant distribution of mass to make an additional zoom that this alone could not do eye in orbit of the noosphere. In this case, it was the WHL0137-08 cluster of galaxies that broke the previous record for a solitary star. Indeed, Hubble had then managed to look into a time when the observable cosmos was only 4 billion years old.
Video taken from the documentary The Odyssey of Light “. In a vacuum, light usually travels in a straight line. But in a space deformed by a massive celestial body, like a galaxy, this trajectory is deviated! Thus, a light source located behind a galaxy has an apparent position different from its real position: this is the phenomenon of gravitational mirage. © CEA, Animea
The discovery is published today via an article in the newspaper Nature, where we also learn that Earendel was a star of at least 50 times the mass of the Sun, making it one of the most massive known. However, the theory of stellar structure and evolution also tells us that this kind of star can only live for a few million years at most. She certainly exploded in supernova SN II a very long time ago, leaving behind a compact star which must be a neutron star or a stellar black hole.
For us, it is still present and it will certainly be studied in more detail in the near future with the telescope. James Webb.
Hubble broke a new record, as this video explains. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © NASA’s Goddard Space Flight Center
Earendel, a type III population star?
The data that the James-Webb will collect will already be used to clarify the nature and properties of Earendel because even if the gravitational lens produced by the galaxy cluster has already enabled us to estimate some of them, such as its temperature, mass and its radius, there are still uncertainties on this subject. In fact, Earendel could be a double star for example.
The most interesting perspective would be that we are in front of a star formed from the gas almost pure from the Big Bang, i.e. a mixture of hydrogen andhelium which would have been almost unchanged by the production of heavier cores, carbon andoxygen notably, in the very first stars. It is believed that these must have been different and notably more massive than the stars that formed in the galaxies billions of years later. Thus, Earendel could look a lot like these primitive stars that are said to belong to a type III population, because they are very old.
the Sun is part of the stars of the type I population and the stars older than 10 billion years, not very massive and therefore long-lived, which are found in the globular clusters or the stellar halos of galaxies are part of type II populations.
Astrophysicist Rogier Windhorst tells us about his discovery of Earendel and star populations. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © ASU School of Earth and Space Exploration
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