Death Star

Nature news has an interesting bit about a death star pointing straight at earth.

You see that spiral? that a binary star system about to explode, well "about" in astrophysics is actually a precise unit of time that means "in a 100,000 years". The death-star is 8,000 light years away.

The scary part is the spiral pattern you see is symmetric and therefore you are staring straight down its axis. The article points out that a certain type of explosion (spherical) would dissipate the effect. However another type with a burst of gamma-rays along the Z-axis would be equivalent to a laser beam hitting us: no dilution of the effect.

What then? mass extinction. First the ozone layer breaks down, then we wash in UV radiation and from there on it is game-over, the same as nuclear war on earth. Apparently a massive UV wash/gamma ray wash has been proposed as a reason for mass-extinction on earth in the past, akin to the "meteor" hypothesis.

From Nature:

Caught in the beam

A mass-extinction event on Earth some 450 million years ago might have been triggered by a gamma-ray burst. Adrian Melott at the University of Kansas in Lawrence, who suggested this in 2003, says that the new observations of WR 104 are big news because this is the first candidate system spotted that could produce a similar Earth-walloping gamma-ray burst in the future. “If it were a full gamma-ray burst and we were caught in the beam, the effects would be pretty severe,” says Melott. “My guess is that there would be a lot of death from it, rather like a small-scale nuclear war.”

A gamma-ray beam might not kill us all immediately. First there would be a bright flash, possibly blinding people, says Melott, then after a few hours the effects would begin in earnest.

The gamma rays would break up molecules in the atmosphere, producing particular oxides of nitrogen that would start to eat up the ozone layer after a few hours, says Melott. Within a few days a quarter of the ozone layer would be destroyed, he suggests.

The ozone destruction would allow through enough ultraviolet light to cause severe radiation damage to plants and people. The nitrogen oxides would also cause acid rain that could kill off plants and algae.
In a spin

But it is impossible to predict whether WR 104 will produce a gamma-ray burst, or when it might happen. For it to occur, the star has to be spinning fast enough to make an axis for the gamma-ray beam to emerge. “Here is where things get a bit more complicated and murky,” says Tuthill, who says he doesn’t know whether WR104 is spinning fast enough.

The fact that this is a binary system could mean that the spin is high, says gamma-ray expert Craig Wheeler at the University of Texas at Austin. “In a binary system the two stars yank each other around and spin each other up,” he says. But Wheeler says he isn't yet scared of what is rapidly becoming known as the Death Star. “I’m not going to worry about it at all.”

There are, certainly, more concrete dangers to worry about, and many questions to answer before we all duck for cover. “WR 104 is now in the last-known stable phase of a massive star. It should explode as a supernova within a few hundred thousand years. Of course, this could mean tomorrow, we have no way of telling,” says Tuthill.