A new discovery could rewrite the account books on the Milky Way . accord to a fresh study published in the Monthly Notices of the Royal Astronomical Society , our galaxy absorbed a pocket-size orbiter galaxy several million years ago . But more than that , it was a celestial event that culminated in the coming together of each galaxy ’s central black hole . The ensuing collision resulted in a cataclysmal event that blast a swath of old star straight out of the core neighborhood at hypervelocity speeds .
The theory , put forth by Kelly Holley - Bockelmann of Vanderbilt and Tamara Bogdanović of Georgia Tech hint that our galaxy has had a violent past — and it may not have been the only confrontation like it over the course of its story .
Holley - Bockelmann and Bogdanović get going to suspect something after studying Fermi Bubbles — two giant lobe of extremely up-and-coming diffuse da Gamma - ray light that are bursting from the center of the galaxy straight above and below the galactic planing machine .
“ Right now , each lobe is about 25,000 light years across , ” Holley - Bockelmann told io9 . “ Scientists know that gamma - shaft lighting issue forth from the most energetic physics known , but we still do n’t completely understand what made these bubbles . ”
The astronomers suspect that particles ignite from the astronomical centre at nearly the speed of light , and then slammed into the ambient interstellar gas — a in high spirits - speed collision industrious enough to make just this form of gamma ray .
But two clues in particular facilitate the squad figure out what drove the Fermi Bubbles .
“ The first cue was that the edges of these bubbles are passing sharp , which made us think that whatever made the Fermi Bubbles was a very abrupt event , ” said Holley - Bockelmann . “ By take the current size and running the clock backwards , we could figure out that the Fermi Bubbles were made a few million year ago .
This was the 2nd clue , she noted , because it matched the ages of the new ace mould at the galactic center field — which made the researchers conceive that both were due to the same culprit .
“ at last , we distrust that natural gas was disturbed by a passing satellite galaxy , and some of the gas made stars , while the rest funnel into the supermassive shameful hole , ” she said . “ The Fermi Bubbles can be thought of as the explosive ‘ burping ’ of the supermassive ignominious mess after a gas - rich repast . ”
And what a meal it must have been . After collaborating with Meagan Langto , Pau Amaro - Seoane , Alberto Sesana , and Manodeep Sinha , the researchers were able to piece together a chronology of events .
Things start to unpick for the small planet galaxy about 13 billion years ago when it — and the intermediate - sized black fix lurking within it — fell towards the kernel of the Milky Way galaxy . As it wound its way deep into our galaxy and towards its astronomical core , it was gravitationally strip of its stars and dark matter until it became a mere skeleton in the closet of its former ego .
Then , a few million years ago , the shredded artificial satellite last reached the galactic center .
“ But by this fourth dimension it was just the black hole and a shroud of mavin and dark matter , ” Holley - Bockelmann severalize us . “ Still , it was massive enough that as it souse through the final few hundred light twelvemonth , it perturbed the gas that was calmly orbiting the galactic center , compressing some of it to organise a outburst of new stars , and drive the relaxation of it to fuel the supermassive bootleg kettle of fish , which in short after let out an volatile Fermi Bubble ‘ burp ’ . ”
And that ’s when thing started to get even more interesting .
The middleweight disastrous hole fall off so near to the Milky Way ’s center that it became intricately bound to its supermassive shameful hole , thus becoming a binary grim muddle .
“ Once the two sinister holes made a binary , they embark on zooming around each other in a in high spirits speed orbital dancing that fling out thousands of stars that cut near distich , ” she noted .
And it was this relativistic grim maw terpsichore that do our galaxy to fling out score of its onetime champion from the core ’s vicinity . The forcefulness involve must have been incredibly acute for this to happen ; the Milky Way ’s supermassive black hole weighs about four million solar masses and is about 40 light irregular in diameter — only nine times the size of our sunlight .
The researchers say that those champion should still be belt along through outer space , about 10,000 light years from their original domain .
And interestingly , this satellite infall event may help to explain not just the Fermi Bubbles , but also why the galactic core area is relatively devoid of previous stars . Models predict that the density of old asterisk should increase with law of proximity to the centre . But our galaxy has very few honest-to-god stars within several light age of the black hole .
In addition , the astronomic center contains the three most massive clump of young star in the wandflower ( include the Central , Arches , and Quintuplet cluster ) . These are stars that should sting out relatively promptly on invoice of their extreme brightness . The only sane account , say the researchers , is that there must have been a relatively late burst of star formation in the neighborhood .
And indeed , Holley - Bockelmann and Bogdanović are evoke that the galactic merger trigger a brief epoch of strong ace formation . In their paper , the author admit that the hypothesis is “ not beyond reproach , ” but that it does a good job explaining all these astronomical anomaly .
Moreover , these infall events may not be rare across cosmogonical timescales . Their simulation designate that infall event could happen once every one billion years .
“ This mean that there may have been other bursts of hypervelocity star ejections , which can sow a population of ‘ internal stars ’ further out in the doughnut of the Galaxy , ” they noted in the study .
Looking ahead , Bogdanović and Holley - Bockelmann plan to publish a paper about these hypervelocity stars in particular .
Their newspaper , “ Can a Satellite Galaxy Merger Explain the participating Past of the Galactic Centre ” has been publish in Monthly Notices of the Royal Astronomical Society .
Images : Top : an artist ’s example of a orbiter galaxy falling into the submassive fateful hole at the center of the Milky Way galaxy ( Julie Turner , Vanderbilt University ) . Interior images NASA ; JPL via Harvard - Smithsonian Center for Astrophysics ; Chandra X - Ray Telescope .
AstronomyBlack holesMilky WayScienceSpace
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