2023-10-07 17:46:27
– The Milky Way, a disturbing discovery
It would be less massive than expected and its rotation curve is atypical compared to other spiral galaxies.
Published today at 7:46 p.m.
Our Milky Way, a magnificent spiral galaxy.
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In astrophysics, we often seek to solve mysteries nestled at the edges of the universe. But it is not always necessary to go so far in time and space to encounter the unexplained. The Milky Way, our galaxy, even provides us with an example, and it is particularly tough. This would in fact be less massive than previous calculations suggested, with a total mass equivalent to 206 billion times that of the Sun. Factor four to five times lower than all the estimates previously issued.
We know this thanks to the mapping issued by the Gaia space mission, which was launched in 2013. Thanks to its two telescopes, the Gaia satellite scanned in detail all the stars of the Milky Way, patiently listing them by assigning them to each a sort of identity card.
The invisible matter
Concerning our galaxy, this new value, revised downwards, perhaps means that the Milky Way ultimately contains less dark matter than we thought. As a reminder, dark matter is invisible, and can only be detected (deduced would be more accurate) from the gravitational effects of surrounding stars. It thus explains why galaxies hold together, and especially why they are so fast. On the other hand, dark matter has never been formally attested and remains hypothetical to this day.
But in addition to this downwardly revised mass, another piece of data throws all the calculations into disarray. The Milky Way, as we know, is one of the spiral galaxies. A study revealed at the end of September in the journal “Astronomy & Astrophysics” reveals that its rotation curve is indeed atypical. It is not flat, as is usually the case with spiral galaxies, but begins to decay rapidly.
A so-called “Keplerian” decay because it follows Kepler’s laws which, as we recall, define the rotation of the satellites according to their distance from the main body. To put it simply, the further away a satellite is from the body that orbits it, the lower its rotation speed, which is basically quite logical. A law which applies for example to the planets of our solar system.
Amazing observation
Hence the amazement that astrophysicists were able to have upon discovering this information resulting from the cartography and observations of the Gaia satellite. To the point of wondering if the famous dark matter really exists. Everything here is just speculation and theories. And these are so numerous that we cannot supposedly mention them in these pages.
Exotic hypotheses have even appeared. Such as the one postulating the existence of antigravity to characterize certain particles. Which would induce the presence of negative masses in the universe and would exclude the intervention of any dark matter or energy. Please note that the probability that this hypothesis is true is extremely low.
Read alsoPascal Gavillet has been a journalist in the cultural section since 1992. He mainly deals with cinema, but he also writes on other fields. Especially science. As such, he is also a mathematician.More information@PascalGavillet
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