On either side ofare two giant bubbles of X, gamma and , which forms a kind of “8” centered at the level of the galactic disk, or more precisely of the galactic center. Discovered by chance when researchers tracked in 2010 using Fermi Gamma-Ray, these well-defined bubbles span nearly 25,000 on each side of the disc. Furthermore, they continue to expand at a rate of 1,000 km/s. According to the researchers, they would be three million years old, with a of between 1 and 100 GeV.
Their origins remain mysterious
But where do they come from? What were they made of? Given the special symmetrical shape of the Fermi bubbles, they could come from the galactic center, more precisely from. This one would spit out high energy matter from its . But a substructure located in the brightest region has intrigued an international team of researchers and is the subject of a publication in .
This substructure, called according to the study, ” that», is closest to the galactic center and contains warm to over 8 million so until today it was interpreted as coming from the same source as the rest of the Fermi bubbles.
Actuallymay have accreted a large amount of matter several million years ago, resulting in the ejection of gas and dust under high temperature and high velocity. This hypothesis, which did not reach consensus, has just been contradicted by the new study!
According to the researchers, the bottom of the bubbles “is probably due toSagittarius Dwarf Spherical ». It is about 50,000 light years from the center of the Milky Way and around our galaxy, which is being torn away little by little . Although it is no longer producing stars, according to the study, it would host a real one “population of milliseconds”that is, off rotating at breakneck speeds.
The Sagittarius galaxy is hidden behind the galactic disc
But above all, “This large satellite of the Milky Way is seen through the Fermi bubbles from the position of», hence the researchers’ hypothesis, according to which it is actually only her that we see at the bottom of the bubbles ! Or rather the millisecond pulsars it would contain. To be sure, they modeled several possible scenarios, including scenarios from central and dwarf galaxies. It is the latter case that best corresponded to the observed measurements.
The gamma-ray sky hosts a pair of giant galactic bubbles. The Fermi bubbles were discovered in 2010, and scientists still aren’t sure what made them, when they formed, or why they look so smooth. They remain a fascinating mystery! https://t.co/SpGzNMkqbJ#NoRhymeOrReasonDaypic.twitter.com/1dSNB6bPeE
—NASA Universe (@NASAUniverse) 1 September 2022
As for the millisecond pulsars in the Sagittarius galaxy, the researchers identified them as being responsible for elimination. No collision in the interstellar medium as gas from the galaxy was sucked in by the Milky Way. No supernovae either, because the latter release gas and the Fermi bubbles contain none. All that remained were the millisecond pulsars, the remnants of dead massive stars that emit powerful radiation from their poles.
A result that could complicate the search forbecause it is especially detected by gamma radiation emitted when dark matter particles and those mutually annihilate each other. Finally, for researchers, “This finding plausibly suggests that millisecond pulsars produce significant γ-ray emission among old stellar populations, which could confound indirect searches for dark matter in regions such as the galactic center, and other dwarf galaxies in the Milky Way. »