James-Webb dives into the gigantic suns of the Westerlund 1 cluster

What can we say in the face of so much beauty? Consider that in the Westerlund cluster (Altar cluster in French), each star is very young, less than 5 to 10 million years old. An age that would be equivalent to a few weeks of the life of a human infant. It is therefore a kind of space nativity scene that we observe in this photo captured by NASA's James-Webb telescope. Observing so many stars in their diversity and so close to each other is a fantastic opportunity to learn more about these cradles of matter.

From supermassive suns to hypergiants and explosives

This cluster is about 13,000 light years away, much further than the most famous open cluster, the Pleiadeswhich can be observed with the naked eye throughout the winter. Astronomers have counted between 50,000 and 100,000 times the mass of the Sun, which is simply colossal for this type of constituent of the Universe. The scientists who have carefully studied it present its most remarkable members:

• 24 so-called Wolf-Rayet stars: they are each dozens of times the mass of our sun and are so hot that their surface is explosive, until the final instability ending in supernova
• Very rare blue and yellow hypergiant stars
• Four red supergiants, which are stars at the very end of their lives, like the very famous Betelgeuse
• A hundred white and blue supergiants (known asOB association)

The Westerlund Cluster offers a unique window into the fascinating stellar evolution. Remember that James-Webb, as a telescope exclusively dedicated to infrared, has the power to pierce dust clouds, in particular thanks to its partly French MIRI instrument. And this is very good, given that Wolf-Rayet stars regularly eject enormous amounts of dust!

Here is another carbon-rich Wolf-Rayet, imaged by the James-Webb MIRI instrument. Look at these fascinating wave structures, they are due to the interaction between the very massive star and its companion star.

Here we are “inside” Westerlund 1.

But why do the stars seen by the JWST always form branches?

The “branches”, which suggest that the stars have the shape that children draw them and such as those on top of our Christmas trees, are in fact optical phenomena. In reality, suns are immense and rather round balls of gas. This being said, the structure of the telescope diffracts the light received by the mirror and creates these figures aptly called “diffraction”. Hubble, whose structure is simpler, only made a cross. James-Webb offers a pattern with eight diffraction peaks (or peaks).

If you are interested in this phenomenon, we recommend that you follow the account X (ex-Twitter) And Blue Sky by the French astrophysicist Lucie Leboulleux, who is a specialist in this phenomenon.

Here are the diffraction peaks produced by the Hubble Space Telescope.