Five galaxies that seem to “communicate” with each other challenge our model of the Universe

How strange is this quintet of galaxies identified by a recently published study by a team of astronomers. These dwarf galaxies are lightweights, their average star mass being measured at some 80 million times that of our Sun, which is very little compared to our galaxy which has around 200 billion. These five are also all more or less aligned with us along an axis, but that's not the strangest thing about it…

What really boggles the mind of the astronomers who have looked into their case is that there appears to be a connection between these galaxies, as if they share common physical characteristics. Their almost straight distribution is already surprising, but the most unusual thing is that members D1, D2 and D5 of this group have similar rotation directions! Of course, such a shared characteristic could be a simple matter of chance, but this probability is scientifically really, really low.

The direction of rotation of a galaxy can be seen by the Doppler effect

The Doppler effect is what explains why the siren of the ambulance approaching you becomes louder in your ear and lower as it moves away. Light frequencies also undergo a Doppler effect: thus, a light which advances towards the observer shifts towards the blue and towards the red when it moves away. We can therefore determine in which direction a galaxy rotates.

The only explanation for the phenomenon: a type of dark matter

Issue : the cosmological standard modelthe one who describes the properties of the currently observable Universe, cannot explain that galaxies can “communicate” in this way, for the simple reason that so-called cold dark matter (Cold Dark Matter for short) implies their hazardous distribution. .

We must therefore look for another candidate for dark matter, and the one that sticks would be the warm dark matter. Why cold, warm or hot? These are adjectives which qualify its capacity to self-interact or not. Cold dark matter only interacts through gravity, warm dark matter has a weak capacity for interaction (the WIMPS Or sterile neutrinos are hypothetical examples). But this type of dark matter is not currently favored by the entire community of particle physicists.

In short, mystery… As Galileo would have said: “And what’s more, they film together!”

Sources:
Astrophysical Journal Letters
arXiv