A strange barrier is keeping cosmic rays out of the Milky Way’s centre

3 years ago 462

The precise centre of the Milky Way has an unexpectedly debased density of cosmic rays compared with the remainder of the galaxy, which means that they are someway being kept out

Space 9 November 2021

By Leah Crane

Something is keeping cosmic rays retired of the centre of the galaxy. The Milky Way is suffused with a oversea of high-energy particles spewed retired by supernovae and different energetic astrophysical objects, but that expanse of cosmic rays seems to beryllium unexpectedly blocked retired of the precise mediate of the galaxy.

Xiaoyuan Huang astatine the Chinese Academy of Sciences and his colleagues examined information from the Fermi Gamma-ray Space Telescope connected the organisation of cosmic rays adjacent our galactic centre. They recovered that portion the cosmic ray density was reasonably changeless successful areas extracurricular the precise centre of the galaxy, it drastically dipped successful the cardinal molecular portion (CMZ), the country closest to the Milky Way’s middle.

This means that thing is keeping the oversea of cosmic rays retired of the CMZ. “If determination is nary barrier, the cosmic ray oversea constituent should besides beryllium contiguous successful the CMZ region,” says Huang. “However, the information bespeak that it is conscionable the other and a obstruction indispensable beryllium present.”

Most cosmic rays are charged particles, truthful a sufficiently beardown magnetic tract would beryllium capable to alteration their paths. “It is apt that stronger magnetic fields beryllium successful the CMZ than outside, which whitethorn artifact cosmic rays from penetrating into the CMZ,” says Huang. “In addition, determination whitethorn beryllium magnetised winds, driven by the enactment of the central supermassive achromatic spread Sagittarius A*, which besides assistance halt particles from entering the CMZ.”

This is akin to a process that occurs successful our ain star system, successful which comparatively low-energy cosmic rays are blown distant by some the magnetised solar wind and the comparatively beardown magnetic fields passim the system.

It could besides hap connected adjacent larger scales, which could impact immoderate extragalactic cosmic rays trying to get into the Milky Way, the researchers say.

Journal reference: Nature Communications, DOI: 10.1038/s41467-021-26436-z

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