The origin of the Fermi bubbles at the center of the Milky Way is in question

The origin of the Fermi bubbles at the center of the Milky Way is in question

The origin of the Fermi bubbles at the center of the Milky Way is in question

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[EN VIDÉO] Discover the first image of the supermassive black hole at the center of its Galaxy!
A big step forward for our knowledge of these mysterious objects … We have been expecting it from 2019, coinciding with the first image of the black hole M87 *. It’s finally here: the first photo of Sagittarius A *, the supermassive black hole in the heart of the Milky Way! © Futura

On both sides of the Milky Way are two gigantic bubbles of X, gamma and Radio, which form a kind of “8” centered at the level of the galactic disk, or more exactly at the galactic center. Discovered by accident while researchers were monitoring the black matter in 2010 using the space telescope Fermi Gamma-Ray, these well-defined bubbles span nearly 25,000 light-years on each side of the disk. In addition, they continue to expand at a speed of 1,000 km / s. According to the researchers, they would be three million years old, with a power gamma rays between 1 and 100 GeV.

Their origin remains mysterious

But where did they come from? What were they created from? Given the particular symmetrical shape of the Fermi bubbles, they could come from the galactic center, more precisely from the central black hole, Sagittarius A *. This would spit high-energy matter from its accretion disk. But a substructure located in the brightest region has intrigued an international team of researchers and is the subject of a publication in Astronomy of nature.

This substructure, called, according to the study, ” the cocoon “, it is closest to the galactic center and contains gas hot to over 8 million degrees Celsius so much so that, until today, it was interpreted as coming from the same source as the rest of Fermi’s bubbles.

In fact, the central black hole Sagittarius A * may have accumulated a large amount of matter several million years ago, causing gas and dust to be expelled at high temperatures, and speed. This hypothesis, which however did not obtain consensus, has just been denied by the new study!

According to the researchers, the base of the bubbles “is probably due to the galaxy Spheroidal dwarf Sagittarius “. It is about 50,000 light years from the center of Milky Way And orbit around our Galaxy, being gradually torn away stars. Although it no longer produces stars, it would host, according to the study, a real one “millisecond pulsar population”namely ofneutron stars spinning at dizzying speed.

The Sagittarius galaxy hides behind the galactic disk

But most of all, “This large satellite of the Milky Way is seen through the Fermi bubbles from the position of the Solar system “, hence the hypothesis of the researchers according to which, in fact, it is only she that we see at the base of the bubbles of Locked down ! Or rather, the millisecond pulsars it would contain. To be sure, they modeled several possible scenarios, including that of the issuance of black hole central, and that of dwarf galaxy. It is the latter case that best corresponded to the observed measurements.

As for millisecond pulsars within the Sagittarius galaxy, researchers have identified them as responsible for elimination. No collision within the interstellar medium, as gas from the galaxy was sucked into the Milky Way. No supernova or, because the latter releases gas and Fermi bubbles do not contain any. All that remained were millisecond pulsars, the remnants of massive dead stars emitting powerful radiation from their poles.

A result that could complicate the search black matterbecause it is detected in particular by the gamma radiation emitted when dark matter particles and the antiparticles annihilate each other. Finally, for researchers, “This discovery plausibly suggests that millisecond pulsars produce significant γ-ray emission among ancient stellar populations, which could confuse indirect searches for dark matter in regions such as the galactic center, the andromeda galaxy and other dwarf galaxies in the Milky Way. “

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