eROSITA X-ray telescope discovers a new hourglass-shaped structure in Milky Way

The Fermi bubbles are two blobs of massive structures in the gamma rays which were discovered by astronomers over a decade ago. These cannot be observed with a naked eye, however, they are incredibly bright in gamma-ray emissions, which is the most luminous and energetic electromagnetic light. It was these gamma rays that had led to their discovery.

These massive outflows span over half of the visible sky. One blob extends 25,000 light-years above the Milky Way's disk, while the other can be found just under it. However, these blobs have long remained a mystery for our galaxy.

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Researchers find massive hourglass-shaped structure similar to Fermi bubbles

Researchers have now found a huge hourglass-shaped structure as part of an all-sky survey that was undertaken using an eROSITA X-ray telescope. These have been called the "eROSITA bubbles" and they are found to be quite similar to the Fermi bubbles.

Here is a schematic view of the Fermi bubbles (indicated in purple) and eROSITA (indicated in yellow). The image shows the difference in size between the two bubbles.

Image credits: MPE

These bubbles bear similarity to the Fermi bubbles, however, they are not as large and also have less energy. Similar to the Fermi blobs, the eROSITA bubbles extend approximately 14 kiloparsecs below and above the Galactic centre. The eROSITA bubbles have sharp borders that have the ability to detect non-radiative and collisionless shocks, and they are only visible in X-ray emissions.

This is a false colour map which highlights the X-ray bubbles in green and red colours.

Image credits: MPE/IKI

This is a false colour map which highlights the extended emission at energies of 0.6-1.0 keV.

Image credits: MPE/IKI

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Considering that both Fermi and eROSITA bubbles come in a similar hourglass-shaped structure and midpoint, it is safe to believe that the two could have some kind of a physical connection. It is also likely that both the outflows have appeared from a shared eruption of galactic fireworks a long time ago. However, it is still not known as to what was the real cause or source of the bubbles, however, scientists believe that it could possibly have something to do with a huge outburst of energy from the Galactic black hole.

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It is likely that the black hole could have been active in the past connecting it to the AGN with the fasting growing black holes observed in faraway galaxies, however, it is dormant right now. According to eROSITA Principal Investigator, Andrea Merloni, the blemishes which are left by these massive outbursts take a considerable amount of time to heal in the haloes.

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Image credits: MPE/IKI