Stars at the edge of the Milky Way are too slow – 'there's something wrong somewhere'

The stars at the edge of the Milky Way are moving more slowly than expected. This surprising discovery raises new questions.

CAMBRIDGE – Like many other galaxies in the universe, the Milky Way galaxy spins like water in a vortex. This rotation is driven in part by the matter in the galaxy. But that's not all: In the 1970s, scientists discovered that visible matter alone cannot fully explain the rotation of galaxies, and researcher Vera Rubin was one of the first to discover dark matter in this way.

Dark matter gives a “boost” to more distant stars in the galaxy

Dark matter, the existence of which has not been proven beyond a reasonable doubt, appears to ensure that all stars within the galaxy have the same speed – and this does not decrease with increasing distance. It's as if invisible dark matter gives distant stars a “boost,” the theory goes. But what about our Milky Way galaxy? A research team from the Massachusetts Institute of Technology (MIT) has measured the speed of stars in the Milky Way and has come up with fascinating new insights.

“It turns out that it is difficult to measure the rotation curve when you are inside a galaxy,” explains Xiao Wei Ou in one of the articles. notice. Or he is one of the authors of the study published in the journal Monthly Notices of the Royal Astronomical Society published had become.

The stars at the edge of the Milky Way are very slow, which is an indicator of the galactic center

The research team used data from the European Gaia spacecraft and the ground-based Apogee program to determine the distances of more than 33,000 stars in the Milky Way. This led to a three-dimensional map depicting the distribution of stars in the Milky Way. The team then created a rotation curve that showed how fast stars were moving at a given distance from the galactic center. “This is where the weirdness starts,” says co-author Lina Naguib, a physics professor at MIT.

“What really surprised us was that this curve remained flat, flat, flat up to a certain distance, and then it started to decrease,” the researcher explains. “This means that the outer stars are rotating a little slower than expected, which is a very surprising result.”

The center of the Milky Way is likely less dense than expected

Unlike previous turnover curves that showed a slight decline, the curve ended up falling more than expected. Using the new rotation curve, the research team was able to recalculate the distribution of dark matter in the Milky Way to understand why exostars move more slowly than they should.

Indeed: The results showed that the center of the Milky Way appears to contain a lighter core than previously thought. This means that the center of our galaxy may be less dense and contain less dark matter than previously thought. “This result contradicts other measurements,” explains Najeeb. “There's something fishy out there somewhere, and it's very interesting to find out where that is in order to get a coherent image of the Milky Way.”

“Really understanding this finding will have profound implications.”

The team plans to find answers to the questions raised by the study in future research projects. “Really understanding this result will have profound implications,” Najib asserts. “This could lead us to find more hidden masses beyond the edge of the galactic disk or make us rethink the state of equilibrium in our galaxy.”

Recently, another research team showed that the Milky Way may look very different than we previously thought. But the Milky Way Galaxy is not the only one that holds surprises for science, there is another surprising galaxy as well. (unpaid bill)

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