Cosmic feat: James-Webb captures 44 isolated and very distant stars thanks to a unique gravitational effect

Even amateurs, all astronomers know it: it is extremely difficult to observe a single star – we say “resolve” – outside our galaxy. With the most powerful telescopes, we normally see entire, sometimes blurry, very distant galaxies, but not the suns that constitute them. At best we will see some sort of lumps made up of packets of stars.

The umpteenth astrophysical feat enabled by NASA's James-Webb infrared space telescope is all the more admirable since it is not one, but 44 individual stars that have been identified within a galaxy located approximately 6, 5 billion light years! Such a challenge was made possible thanks to two strokes of cosmic fate which we will explain here…

For two lentil dishes, Abell 370 offers stars in a dragon

Okay, it's Jacob who offers lentils in the Bible, and not Abel… No matter, it's once again a physical principle of gravitational lens which here magnified, increased and distorted the distant light of the Dragon Arc, originally received by the Hubble telescope. Here is the Abell 370 cluster where we notice several very distorted galaxies, one of which resembles a sort of Chinese dragon, or even a snake:

Even stronger – and somewhat fortunate – a second gravitational lensing effect is observable, less powerful than the first. The first gravitational lensing is due to a cluster of galaxies, which amplifies the light about 100 times, but the second is due to an alignment of stars in the already lensed galaxy, what astronomers call “microlensing”. This made it possible to image single stars at a distance of 6.5 billion light years, which James-Webb usually cannot do without this fortuitous alignment.

Here is what James-Webb was able to see:

Many red supergiants like Betelgeuse or Antares

In their study published on Natureastronomers note that for once, these are not blue giants such as Rigel which could be observed so far away, but red supergiants of the type Betelgeuse Or Antareswhich respectively illuminate our winter and summer skies with their ruby ​​radiance. These stars being “colder” than their blue counterparts, James-Webb and its very high sensitivity to infrared are particularly equipped to spot them.

In addition to being an incredible opportunity to observe the evolution of stars so distant from us (thus born a very long time ago), gravitational lensing effects are an excellent way to learn more about dark matter, because this amplification is one of the many signs that matter other than “ordinary” matter is present in these galaxy clusters.