2023-08-05 17:09:40
Kaiju stars are abnormally bright stars for their mass and size. They are rare but the James-Webb Space Telescope looked at two of them recently using the gravitational lensing effect. The observations obtained refute certain models of dark matter particles by placing bounds on the masses of the particles of these models.
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In recent centuries, astronomers gave the names of Greco-Latin deities to the stars they discovered. This was the case, for example, for Pluto, discovered by American astronomer Clyde Tombaugh in 1930, or for Janus, the moon of Saturn discovered in 1966 by the French astronomer Audouin Dollfus.
Modern astronomers have other mythological sources, four colliding galaxies have thus been named ” The Fantastic Four at the time of the release of an eponymous Marvel film and now two abnormally bright stars, and therefore which one might believe abnormally large, have been baptized not only “kaiju” stars but also Mothra and Godzilla as one can be convinced of this by consulting an article recently posted on arXiv and not yet published.
let’s remember that Kaiju (怪獣?, lit. “strange beast” or “mysterious beast”) is a Japanese term for strange creatures, particularly famous giant movie monsters that have become iconic, such as precisely Godzilla and Mothra ( モスラ, pronounced “Mo-su- ra” in Japanese version).
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. This video originates from the web documentary “The Odyssey of Light” and was integrated into the web documentary “Aboard with dark matter”. © CEA, Animea
Small concentrations of dark matter growing stars?
Here, the team of researchers led by Spanish astrophysicist José Diego called Mothra a star observed by the James-Webb Space Telescope under the scientific name of EMO J041608.8−240358 as it appeared just over 10 billion years old. The JWST used a gravitational lensing effect to more easily probe the observable Universe at great distances, which of course makes the stars brighter, but both Mothra and Godzilla — which outshines Mothra to the point of earning the title of brightest star so far known in the noosphere — are too bright for lensing caused by a galaxy cluster.
In fact, everything indicates that Mothra is in fact probably a binary system composed of two supergiant stars, one red and one blue.
The red star is cooler and dimmer, with a blackbody surface temperature of regarding 5,000 kelvins and a luminosity of 50,000 Suns, while the blue star has a surface temperature estimated at 14,000 kelvins and has a luminosity of regarding 125,000 suns.
To account for the apparent excess of luminosity, astrophysicists propose the existence of another distribution of matter present between Mothra and us, and which, by its gravitational field, adds an additional gravitational lensing effect.
But, for that, it is necessary to bring in a concentration of dark matter, probably in the form of a dwarf galaxy (perhaps ultra-diffuse, which would then raise questions), with few stars and containing between 10,000 and 2.5 million times the mass of the Sun.
Limits on the masses of dark matter particles
The Cosmological Standard Model predicts the existence of small concentrations of similar dark matter, and the fact that it is observed so quickly with the JWST implies that there must be a lot of them.
However, if this hypothesis is correct, the characteristics of those that would be observed with Mothra and Godzilla as well are likely to constrain the types of dark matter particles theoretically possible. This would be the case in particular for models with the famous particles that are generically called axions.
We should learn more regarding the subject with the study of other anomalously bright “kaiju” stars with regard to what we can expect from the luminosities allowed by the standard and well-tested theory of star structure (see for example on this subject the famous work of Francis LeBlanc).
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