The Milky Way Galaxy Center is now a relatively quiet place (compared to other galactic centers), but this has not always been the case. In fact, just 3.5 million years ago, it was positively turbulent – ejecting a surge of energy that eventually exploded 200,000 light-years above and below the galactic plane.
The shock waves of this colossal outburst — called the Seifert outburst — can today be observed in the Magellanic Flow, a high-speed gas stream originating from the Great and Small Magellanic Clouds, 200,000 light-years from the Milky Way.  This is so powerful, astronomers believe that it could only come from Sagittarius A *, a supermassive black hole in the center of the Milky Way. Since the first evidence of the outbreak was published in 201
 In 2013, astrophysicist Joss Bland-Hawthorn of the University of Sydney and the International Center for Radio Astronomical Research (ICRAR) and his colleagues estimated that 1 event happened 3 million years ago.
Now, more observations made with the Hubble Space Telescope – and therefore a larger data set – have provided even more compelling evidence of the event. And the team managed to narrow the time frame both at the time of the event and its duration.
"These results dramatically change our understanding of the Milky Way," said astronomer Magda Guglielmo of the University of Sydney.
"We have always thought of our Galaxy as an inactive galaxy with a not too bright center. Instead, these new results open the possibility of a complete rethinking of its evolution and nature."
There are several tips that have helped to make the picture. The clearest are the enormous Gamma and X-ray Fermi bubbles extending above and below the galactic plane, detected by both the Fermi satellites and the ROSAT. In general, these bubbles extend about 50,000 light-years – 25,000 above and 25,000 below the galactic plane.
Then, in 2013, astronomers reported the discovery of hydrogen-alpha emission along a section of the Magellanic flow directly in accordance with the bubble. The most likely explanation for this, they explained, was a surge of ionizing energy from the center of the Milky Way.
What Hubble noticed is another piece of this puzzle. Some absorption coefficients of ultraviolet wavelengths reveal that some of the clouds in the Stream are highly ionized and very energetic.
"We show how clouds that fall into the bundle of bipolar, radiative" ionization cones "from the Seyfert nucleus, associated with Sgr A *," the researchers wrote in their paper.
Basically, two expanding cones, starting from a small region close to the galactic center and extending outwards above and below the galactic plane, blew ionizing radiation down to space, ionizing gas in Magellan in 1965, ] "The glitter was probably a bit like a beacon beam," said Bland-Hawthorn. "Imagine the darkness, and then someone switches on the lighthouse beacon for a short time."
Nothing but powerful black hole relativistic jets could be powerful enough to achieve this effect, researchers
The outbreak occurred about 3.5 million years ago and lasted about 300,000 years. This is a fairly short burst on a cosmic scale.
There was already a Pliocene here on Earth, the period when the most modern species arose.
And although it seems that Sgr A * was relatively quiet during the periods that come into its recent observations suggest that it may be a stir.
"This is a dramatic event that happened millions of years ago in the history of the Milky Way," said astronomer Lisa Keeley of the Australian National University and the ARC Center of Excellence for All Sky Astrophysics in 3D.
"A massive explosion of energy and radiation came directly from the galactic center and into the surrounding material. This indicates that the center of the Milky Way is a much more dynamic place than we thought before."
Our distance is 26,000 light years from the center of the galaxy means we're probably protected from any gigantic outbursts – we seem to have been unharmed by BH2013. If we're lucky, we can see one hell of a light show.
The study was accepted into the Astrophysical Journal and a draft version is available here.