The core of our Milky Way is a normally calm place at present, in comparison to other galaxies, but it hasn’t always been like this. As a matter of fact, about 3.5 million years ago, the galactic center was positively violent. According to some scientists, the Milky Way might have spewed a burst of energy that ultimately exploded 200,000 light-years above and under the galactic plane.
The shockwaves of the massive blaze, known as ‘Seyfert flare,’ can still be seen in the Magellanic Stream, a high-velocity cloud of gas expanding from the Large and Small Magellanic Clouds, about 200,000 light-years from our galaxy.
The blaze is so powerful scientists suggest it could only have originated from Sagittarius A*, the supermassive black hole residing in the nucleus of the Milky Way. The event was dubbed BH2013 because the first evidence for the Seyfert flare was published back in 2013.
In 2013, astrophysicist Joss Bland-Hawthorn of the University of Sydney and the International Centre for Radio Astronomy Research (ICRAR) and his colleagues suggested that the occurrence happened between 1 and 3 million years ago.
We Might Live To See Another Flare Like This
Currently, more data is available from the Hubble Space Telescope, which has provided even more intricate evidence for the massive flare. Scientists working on this research had managed to estimate when the event occurred, and also how long it lasted.
There are numerous pieces of evidence that have aided researchers to complete the whole picture. The most definite clue is the gigantic ‘Fermi bubbles’ of gamma and X-ray radiation, spreading above and below the galactic plane. These bubbles were detected by Fermi and ROSAT satellites. They expand, in overall, approximately 50,000 light-years: 25,000 above and 25,000 below the galactic plane.
Another major discovery was made in 2013, when astronomers reported a hydrogen-alpha emission found through the Magellanic Stream, directly parallel with the bubble. The most probable explanation for this was a burst of ionizing energy from the core of the Milky Way, scientists explained.
Hubble has yet discovered another piece of the puzzle. Some type of absorption ratios in ultraviolet wavelengths suggest that some of the clouds in the Stream are extremely ionized, and by a highly energetic source.
What this means is that two expanding cones, starting from a tiny area near the galactic core and extending outwards above and below the galactic plane, spewed ionizing radiation so far into space, it ionized the gas in the Magellanic Stream, which is hundreds of thousands of light-years away.
The blast happened approximately 3.5 million years ago, and lasted for about 300,000 years, astronomers explained.
Even though it seems like Sagittarius A* has been somewhat quiet in the intermediate years, modern observations suggest it could be moving. The distance between the galactic center and us, about 26,000 light-years, means we are probably safe from any massive blasts. In the end, we seem to have come out unharmed from BH2013.
However, if we are fortunate enough, we might get to see an incredible light show.
The research was published in The Astrophysical Journal.