Could Supernova Explosions Damage Earth?

"This is not going to be an 'everything dies immediately' kind of event," said Brian Thomas at Washburn University. "But with the risk factors associated with higher levels of this kind of light it's certainly something that could be important in the longer run."

Thompson has been studying the effects of astronomical explosions at the Goddard Space Flight Center of late, and has focused his attention at Eta Carinae, a star that for some time has been showing signs of exploding.

From 1838 to 1858 Eta Carinae brightened to match the light of Sirius, traditionally the brightest star in the sky, before slipping back in to obscurity. Since 1940 however, it has been ramping back up again.

Thompson’s research has focused primarily on what effects supernova will have on planet Earth, if any. When Eta Carinae goes kablooie it will be too far away to cause any damage, sitting at some 7,500 light years from Earth.

But Thompson proposed another problem, one that of late has seen some recent press. Towards the end of last year several supernova were found to have brightened considerably. One such supernova, SN 2006gy, was the brightest ever until it was passed by another in November.

Astronomers now know however that the progenitor to SN 2006gy was very similar to Eta Carinae. This proposed the question, what if Eta Carinae detonated with the brilliance of SN 2006gy.

Much to our relief, there is realistically very little that could happen to us if such a detonation occurred. SN 2006gy, though exceedingly bright, expelled very few X-rays, one of the few things that could do us harm from such a distance. The majority of the X-rays and cosmic rays would, according to Thompson and his team, dissipate in the space between us and the explosion.

So, is there no danger then? Not quite, although as mentioned at the top, it won’t be a “…'everything dies immediately' kind of event.”

According to the research optical light – specifically that along the short-wavelength blue light (400 nanometers) – could create some amount of havoc for us on Earth. "The visible light could be significant," Thomas says, "But this depends a little bit on your definition of significant."

If Eta Carina were to explode like SN 2006gy, it would soon assume third brightest object in the sky, after the sun and the moon. In fact, for those of us within the bottom quarter of the planet – where it is always on the horizon – it would greatly outshine Venus, and even appear during the day.

Following that, the radiation would soon light up the sky a pale blue, nearly strong enough to read a book by. This effect could last for months, predicted to be up to six months long. Such conditions would cause havoc with circadian rhythms, increasing chances of insomnia.

Granted, all of this being said, it pays little to worry considering that Eta Carina is expected to detonate sometime in the next 10,000 to 20,000 years.

Posted by Josh Hill.

http://www.livescience.com/space/scienceastronomy/080108-eta-carinae.html