Our Dangerous Galactic Passage

© NASA

Our Dangerous Galactic Passage
Sept 10, 2012 | Ray Villard

We're only a little more than three months away from the imaginary 2012 End of Times (based on silly misinterpretations of the ancient Mayan calendar). The 2012 doom and gloom folks have glommed onto all kinds of nonsensical predictions where the Milky Way galaxy disrupts us: the passage of the solar system across the galactic plane, or a supposed "grand alignment" with the galactic center will trigger a mysterious and nondescript celestial 'force.'

In reality, our Milky Way really does pose numerous hazards to Earth during the sun's orbital journey around the galactic center. But no future space disaster can be circled on a calendar on Dec. 21 or any other date.

The sun has completed 20 orbits of the galactic hub since Earth formed. Each orbit is called a galactic year -- a vast stretch of time (220 million Earth years) that the Mayans could have never imagined. Whatever cosmic catastrophes might have happened along the way, it has not prevented complex life from arising and evolving on Earth over roughly the past three galactic years. There have been attempts at statistically linking mysterious mass extinctions to cosmic disasters, but we simply don't have enough data, says Colin Norman the Johns Hopkins University in Baltimore, Md.

The reality is that the potential of navigational hazards along our galactic journey lie far into the future over many millions or billions of years. Our distant descendants could come up with strategies to guard against some of these mishaps. However, the biggest threat is from extremely rare energetic events in the galaxy, says Norman.

Killer catastrophes were much more frequent in the Milky Way's formative period, billions of years before Earth was born. Stars were being made at such a voracious rate -- and then quickly exploding -- that the galaxy would have been made uninhabitable by the radiation saturation, says Norman.

This is sobering because we suspect there could be ancient Methuselah planets in the galaxy that might have formed 12 billion years ago (as opposed to Earth's 4.5 billion year birthday). But they would have been sterilized of life by radiation from multiple supernova and hot stellar winds from giant stars.

Over time there have been 1 billion supernovae in our galaxy. They accelerate cosmic rays that irradiate any nearby star systems. Even more devastating are so-called Quimby events. These are an unusual class of extraordinarily powerful supernova that defy conventional explanations for their power generation. It's hypothesized that these super-blasts only happen in very rare stars that are over 100 times the mass of our sun. There could have been 10 million of these popping off in our galaxy to date.

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