Astronomers discover enormous ‘barrier’ separating the center of the Milky Way from the cosmic ray sea

The center of the Milky Way could also be much more weird than astronomers thought, in line with a brand new examine.

For the examine, a staff of researchers from the Chinese Academy of Sciences in Nanjing investigated a map of radioactive gamma-rays — the highest-energy type of gentle in the universe, which might come up when extraordinarily high-speed particles referred to as cosmic rays crash into peculiar matter — blasting in and round the center of our galaxy.

The map revealed that one thing close to the center of the galaxy seems to be accelerating particles to mind-blowing speeds — very close to the speed of gentle — and creating an abundance of cosmic rays and gamma-rays simply exterior the galactic center. However, at the same time as the galactic center blows a continuing storm of high-energy radiation into space, one thing close to the Milky Way‘s core prevents a big portion of cosmic rays from different elements of the universe from getting into, the staff reported Nov. 9 in the journal Nature Communications.

The researchers described the impact as an invisible “barrier” that’s wrapped round the galactic center and is maintaining the density of cosmic rays there considerably decrease than the baseline stage seen all through the relaxation of our galaxy. In different phrases: Cosmic rays can get out of the galactic center, however have a tough time getting in.

How this cosmic barrier works, or why it exists, stays a thriller.

Monster in the center

The center of our galaxy is situated about 26,000 light-years from Earth in the constellation Sagittarius. It is a dense and dusty place, holding greater than 1 million occasions as many stars per light-year as the complete solar system — all wrapped round a supermassive black hole with about 4 million occasions the mass of the solar.

Scientists have lengthy suspected that this black hole, named Sagittarius A*, or maybe another object at the galactic center, is accelerating protons and electrons to close light speed, creating cosmic rays that beam all through our galaxy and onward into intergalactic space. These rays propagate by way of the magnetic fields of our galaxy, creating an ocean of high-energy particles that is roughly uniform in density all through the complete Milky Way. This regular soup of particles is known as the cosmic ray sea.

In their new examine, the researchers in contrast the density of cosmic rays on this sea to the density of cosmic rays inside the galactic center. Cosmic rays can’t be seen straight, however scientists can discover them in gamma-ray maps of space, which successfully present the place cosmic rays have collided with different sorts of matter.

Using information from the Fermi Large Area Telescope, the staff confirmed that one thing in the galactic center is certainly performing as an enormous particle accelerator, taking pictures cosmic rays out into the galaxy. Possible culprits embody Sagittarius A*, as black holes may theoretically shoot sure particles into space at the same time as they gobble up all the pieces else round them, Live Science previously reported; the remnants of historic supernovas; and even robust stellar winds from the many stars crammed into the galactic center.


But the map additionally revealed the mysterious “barrier,” a transparent level the place the density of cosmic rays drops off considerably at the edge of the galactic center. The supply of this phenomenon is more durable to pinpoint, the researchers mentioned, however it could contain the jumble of magnetic fields close to our galaxy’s dense core.

For instance, dense clouds of mud and gas close to the galactic center may collapse onto themselves, compressing the magnetic fields there and making a cosmic-ray-proof barrier, the staff instructed of their paper. Or, maybe stellar winds from the myriad stars at the galactic center are pushing again in opposition to the cosmic ray sea, a lot as the solar wind does.

Further analysis is required to determine precisely what is going on in the weird depths of our galaxy.

Originally revealed on Live Science.

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