A gigantic energy blast called Seyfert flare punched out from the center of the Milky Way around 3.5 million years ago. According to astronomers' report on October 6, 2019, more evidence has been revealed relating the Fermi bubbles - apparent remnants of a titanic explosion in our galaxy's center - in the form of two massive bursts of radiation that possibly zipped through our galaxy's poles and out into deep space. One burst must have been so extreme to spread 200 000 light-years into space, and its impact hit the Magellanic Stream - a long trail of gas from Large and Small Magellanic Clouds orbiting the Milky Way.
Astronomers said all of these events from our galaxy's center seemingly happened 3.5 million years. The blast lasted approximately 300 000 years - a very long time in human terms, but a short time on a universal scale.
According to the astronomers who discovered the flare event, "Some Stream clouds towards both galactic poles are highly ionized by a source capable of producing ionization energies up to at least 50 eV," and the ionization is associated to the blast that produced the Fermi bubbles.
10% of all galaxies are said to have Seyfert flares as well. The Milky Way is not generally considered a Seyfert galaxy, but it is known to have a 4-million solar mass black hole at its center named Sagittarius A.
Astronomers are discovering that the Milky Way can occasionally have a burst of activity even though it's not as major as those of active galaxies. The research team said the explosion about 3.5 million years ago was too massive to have been triggered by anything other than nuclear activity related to Sagittarius-A.
The lead author of the study, Joss Bland-Hawthorn from Australia's ARC Center of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) explained, "The flare must have been a bit like a lighthouse beam. Imagine darkness, and then someone switches on a lighthouse beacon for a brief period of time."
Lisa Kewley, director of ASTRO 3D, also commented, "This is a dramatic event that happened a few million years ago in the Milky Way’s history. A massive blast of energy and radiation came right out of the galactic center and into the surrounding material. This shows that the center of the Milky Way is a much more dynamic place than we had previously thought. It is lucky we’re not residing there."
The study is set to be published in The Astrophysical Journal.
Featured image credit: NASA Goddard