Two giant and mysterious bubbles launch from the heart of the Milky Way and now it looks like the bubbles may have doubled.
Scientists have known for a decade that two bubbles of charged particles, or plasma, flank the plane of the Milky Way. These structures, known as Fermi bubbles after the telescope that detected them, are visible in a high-energy light called gamma rays (SN: 11/9/10). But now, the eROSITA X-ray telescope has revealed larger bubbles, seen in X-rays. X-ray bubbles extend about 45,000 light-years above and below the center of the galaxy, researchers reported online on December 9 in Nature.
Previously, researchers saw an X-ray arc over the galactic plane (SN: 8/7/20). But no such feature was evident below the plane of the galaxy. That lack of symmetry has led some scientists to discount the possibility of X-ray bubbles. With the new results, "this argument has already fallen," says study co-author Andrea Merloni, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. . EROSITA data reveal a faint, previously unknown bubble below the galactic plane and a matching bubble above. Merloni says the gamma-ray bubbles are nested inside the X-ray bubbles, suggesting that the two features are connected.
The study of the bubbles could help reveal violent events that may have taken place in the galaxy’s past. The supermassive black hole in the center of the Milky Way is currently fairly quiet, as for the black holes. But a frantic past feeder could have ejected its leftovers out, forming the structures. Or the bubbles may have been the result of a period in which many stars formed and exploded in the heart of the galaxy. A later study of the X-ray and gamma bubbles could help reveal the cause.