The first-ever all-sky X-ray map of our galaxy, provided by the ESA’s eROSITA spacecraft, reveals two massive bubbles. These bubbles extend for up to 50,000 lightyears above and below the Milky Way, and are believed to be remnants of a massive outburst that occurred millions of years ago.
We’ve known for a long time that the inner core of the Milky Way can be a pretty violent place. Clusters of supernovae and the infernal work of our central supermassive black hole can wreak havoc, spreading devastation for light-years.
And now, with a new all-sky X-ray map by the European Space Agency’s eROSITA mission, we can see some of the scars from our galaxy’s violent past.
The map reveals two gigantic bubbles, filled with a hot but thin gas that glows in X-rays, on opposite sides of the galactic disk. The northern bubble, known as the “North polar spur”, had been known to astronomers for decades. But its southern counterpart is new, only revealed by eROSITA’s survey.
eROSITA’s X-ray view of our galaxy, showcasing two massive bubbles extending thousands of lightyears. Image credit: MPE/IKI
Each bubble extends for 50,000 lightyears, making the structures as large as the Milky Way itself.
What could cause these bubbles to form? Astronomers have long suspected that a pair of smaller, hotter bubbles, called the Fermi bubbles, were launched when our central supermassive black hole violently expelled gas from its vicinity in a single outburst. But those bubbles, and the larger X-ray bubbles recently discovered, may also be caused by a sequence of supernova explosions occurring within the galactic core.
Whatever the cause, it took a lot of energy to blast those bubbles out of the Milky Way – equivalent to 100,000 supernovae detonating simultaneously.
Due to its incredible tenuousness, observing the hot, thin gas thought to surround all galaxies is extremely difficult. But astronomers are hoping to use these new maps to understand that gas and its role in galactic evolution.