Supermassive black hole at heart of galaxy erupted 2 mn yrs ago
Washington: A dormant volcano - a supermassive black hole - lies at the centre of our galaxy last erupted two million years ago, according to scientists.
Astronomers have long suspected that an outburst like this occurred, but this is the first time that they have actually been able to date it.
The proof comes from a lacy filament of gas, mostly hydrogen, called the Magellanic Stream and this trails behind our galaxy`s two small companion galaxies, the Large and Small Magellanic Clouds.
Team leader Professor Joss Bland-Hawthorn, an ARC Federation Fellow at the University of Sydney, Australia said that for twenty years they saw this odd glow from the Magellanic Stream, who cause couldn`t be understood.
He said they suddenly realized that it must be the mark, the fossil record, of a huge outburst of energy from the center of our galaxy.
Evidence has been building of a real cataclysm in the past. Infrared and X-ray satellites have seen a powerful `wind` (outflow) of material from this central region.
Antimatter boiling out has left its signature. And there are the `Fermi bubbles` - two huge hot bubbles of gas billowing out from the galactic center, seen in gamma-rays and radio waves.
Scientists studying the galactic center came together at a workshop at Stanford University in California, where Professor Bland-Hawthorn realized the Stream could be holding the memory of the galactic center`s past.
Struck by the fiery breath of Sagittarius `A-star`, the Stream is emitting light, much as particles from the Sun hit our atmosphere and trigger the colored glows of the aurorae-the Northern and Southern Lights.
In the Stream, ultraviolet light splits hydrogen atoms into protons and electrons. When those components recombine, the electrons give off `H-alpha` emission-a specific wavelength of light.
The brightest glow in the Stream comes from the region nearest the galactic center.
The paper has been accepted for publication in The Astrophysical Journal.
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