– 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 try to solve mysteries that lurk at the edges of the universe. But it is not always necessary to go so far in time and space to encounter the inexplicable. The Milky Way, our galaxy, is even a model for this, and it is particularly hard. This would actually be less massive than previous calculations suggested, with a total mass equivalent to 206 billion times the mass of the Sun. Factor four to five times lower than all previously given estimates.
We know this thanks to the mapping of the Gaia space mission launched in 2013. Thanks to its two telescopes, the Gaia satellite scanned in detail all the stars of the Milky Way and patiently listed them, assigning each one a variety of the ID card.
The invisible matter
In terms of our galaxy, this downwardly revised new value may mean that the Milky Way ultimately contains less dark matter than we thought. As a reminder, dark matter is invisible and can only be discovered (inferred would be more accurate) from the gravitational effects of surrounding stars. It therefore explains why galaxies stick together and, in particular, why they are so fast. On the other hand, dark matter has never been officially detected and remains hypothetical to this day.
But in addition to this downwardly corrected mass, another piece of data messes up all the calculations. The Milky Way, as we know, is one of the spiral galaxies. A study published in late September in the journal Astronomy & Astrophysics shows that its rotation curve is actually atypical. It is not flat, as is usual with spiral galaxies, but begins to decay quickly.
A so-called “Keplerian” decay because it follows Kepler’s laws, which, as we remember, 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 actually quite logical. A law that applies, for example, to the planets in our solar system.
Amazing observation
Hence the amazement that astrophysicists could feel when they discovered this information resulting from the cartography and observations of the Gaia satellite. So much so that one wonders whether the famous dark matter really exists. Everything here is just speculation and theories. And these are so numerous that we supposedly cannot mention them on these pages.
Even exotic hypotheses have emerged. For example, the one who postulates the existence of antigravity to characterize certain particles. This would induce the presence of negative masses in the universe and exclude the intervention of any dark matter or energy. Please note that the probability of this hypothesis being true is extremely small.
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Pascal Gavillet has been working as a cultural journalist since 1992. He mainly focuses on cinema, but also writes about other areas. Above all, science. As such, he is also a mathematician.More information@PascalGavillet
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