Milky Way underwent furious explosion six million years ago

New Delhi: Today, our Milky Way galaxy is very quiet and its center position is occupied by super massive black hole that sometimes sips small amount of hydrogen gas from nearby celestial bodies.

Well, a new study suggest that it wasn't always like this as a massive explosion blownout the core of the galaxy some six million years ago. Researchers from Harvard-Smithsonian Center for Astrophysics said that six million years ago, when the first human ancestors known as hominins walked the Earth, our galaxy's core blazed forth furiously.

New measurements show that the Milky Way galaxy weighs about 1-2 trillion times as much as our Sun. About five-sixths of that is in the form of invisible and mysterious dark matter.

The remaining one-sixth of our galaxy's heft, or 150-300 billion solar masses, is normal matter. However, if you count up all the stars, gas and dust we can see, you only find about 65 billion solar masses.

The rest of the normal matter - stuff made of neutrons, protons, and electrons - seems to be missing.

"We played a cosmic game of hide-and-seek. And we asked ourselves, where could the missing mass be hiding?" said lead author Fabrizio Nicastro "We analyzed archival X-ray observations from the XMM-Newton spacecraft and found that the missing mass is in the form of a million-degree gaseous fog permeating our galaxy.

That fog absorbs X-rays from more distant background sources," Nicastro continued.

The astronomers found that there is a "bubble" in the centre of our galaxy that extends two-thirds of the way to Earth. The bubble required a tremendous amount of energy. That energy, the authors say, came from the feeding black hole.

More answers may come from the proposed next-generation space mission known as X-ray Surveyor. It would be able to map out the bubble by observing fainter sources, and see finer detail to tease out more information about the elusive missing mass. The study was published in The Astrophysical Journal.

(With IANS inputs)