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Sea Life Wiped Out by Neutron Star Collision?
Memorize writes "Scientists report in the Journal of Astrophysical Letters that a mass extinction of marine life 450 million years ago might have been caused by radiation from an exploding star, such as a collision between two neutron stars, or a neutron star collapsing into a black hole. Such an event would cause a ten-second burst of gamma radiation, and if it occurred within our galaxy, it could have wiped out many species on earth. At least if astronomers find out that an asteroid is heading our way, we can do something about it, but if there is a gamma burst, we get no warning. And if we did, would there be any way to protect the planet?"
Gamma ray bursts are an area of active research; we now believe that they emit radiation along some polar axis, rather than isotropically in every direction. That probably accounts for the difference in distances you've seen quoted; for some fixed power level, an anisotropic GRB is dangerous from a greater distance if you happen to lie in the beam.
Given a number of confused responses to this, let's just remind everybody: it's not the gamma rays that kill (they would only get half of the globe anyway), it's the stripping away of the ozone layer followed by intense UV radiation. That's why it's a global effect.
While that would cause huge famines and disease and kill almost all humans, it is something that our species could survive given our technology.
Half the planet (almost) instantly dead, the other side gets insta-sunburn the moment they walk outdoors for the next few years.
The consensus among professional astronomers is still overwhelmingly in support of the existence of black holes.
/ ) PSR J0737-3039 in 2003-4 using the Parkes radio telescope in Australia provides astronomers with an even better testbed.
Your second point about two neutron stars being unlikely to run into each other is not correct. Extensive studies of binary neutron star systems such as PSR B1913+16 and PSR B1534+12 provide stringent checks on general relativity. Each of these systems has two neutron stars orbiting each other with one of the pair also being detectable as a pulsar. Each component in the system is spiralling in towards the other.
The recent discovery of the first known binary pulsar system (see http://www.atnf.csiro.au/news/press/double_pulsar
In this system the two pulsars orbit each other every 2.4 hours, making them some of the fastest-moving stars known. As they orbit they lose orbital energy through gravitational radiation. They move closer together. The rate at which this happens can be determined and inital studies suggest the two pulsars will coalesce in about 85 million years. This system is about 1,600-2,00 light years or 550 parsecs distant from us. I can assure you that astronomers are actively observing and studying this system as it is allows them to test theories of gravity with incredible precision.
Neutron star collisions do/will occur and will produce strong gravity waves and most likely high fluxes of gamma rays.
There are now long-term projects monitoring pulse arrival times from pulsars across the sky with the aim of detecting gravity waves.
If the 6,000 LY limit is justifiable, I don't think it's quite as bad as you make out... at least not without some much more definitive research.
6,000 Light Years is practically next door on the galactic scale. It's certainly not infeasible (for someone qualified) to simply look at a survey of what's in our local space and determine immediately if we're at risk based on anything that looks unstable. (I'm not a professional astronomer, so someone's welcome to correct me if they know otherwise.)
The most obvious potential threat that's relatively close is probably Eta Carinae, which is about as massive as it's possible to get, and it's been hypothesised in the past that there's a small chance we might be at risk from a sudden gamma ray burst from it. But it's still about 8,000 light years away and there's still not enough known about it to have any accurate idea of when it's going to blow itself apart, either tommorrow or millions of years from now.
If there's still a reasonable chance that it could happen at some point in the future, this doesn't mean that there's any chance at all of it happening tommorrow. Stars orbit move a lot relative to each other sa they orbit the galactic centre. Our Sun does that in about 226 million years, but in the space of hundreds of thousands of years, galactic material barely moves relative to each other at all. It's feasible that at some time in the next few million years or more we will be close to something dangerous for some period of time. If we're not close enough to it now, though, the chance of that happening is still zero.
This is all dependent on that 6,000 Light Year limit being correct, of course. Clearly it's still all subject to change as we learn more about the Universe, which we still know next-to-nothing about. I don't think there's much point worrying about the great unknown, though, at least until we know enough to know that there's actually a risk. Otherwise it would just lead to paranoia.
Any gamma burst from a single point will only fall on half the Earth's surface directly. What stops us from just hopping across to the other half, instead of needing scifi tech to survive?
Short Answer: RTFA
Long Answer:
The Gamma rays would destroy the ozone on the unlucky side. Once the ozone redistbutes, you are down to 50% everywhere. That is, aparently, enough to kill plankton. Probably would kill land plants, too.
So, on the unlucky side everybody dies. On the lucky side, crops fail for several years. Very bad news, though I doubt it would actually exterminate the human race. Plants would still grow in UV filtered green houses.
A pre-print of the research article is available. The impression that I get is that they don't claim to really "prove" the idea, but rather pose it as a very interesting hypothesis which is compatible with the evidence and deserves further investigation. In particular, I think their claim is that gamma ray bursts can explain the evidence of rapid cooling from the extinction period. Of course, the popular press claims this tentative hypothesis like it was already a concrete fact, but that's what the press does.
Here's the basic info:
Title: Did a gamma-ray burst initiate the late Ordovician mass extinction?
Abstract: Gamma-ray bursts (hereafter GRB) produce a flux of radiation detectable across the observable Universe, and at least some of them are associated with galaxies. A GRB within our own Ggalaxy could do considerable damage to the Earth's biosphere; rate estimates suggest that a dangerously near GRB should occur on average two or more times per billion years. At least five times in the history of life, the Earth experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and GRB may also have contributed. The late Ordovician mass extinction approximately 440 million years ago may be at least partly the result of a GRB. A special feature of GRB in terms of terrestrial effects is a nearly impulsive energy input of order 10 s. Due to expected severe depletion of the ozone layer, intense solar ultraviolet radiation would result from a nearby GRB, and some of the patterns of extinction and survivorship at this time may be attributable to elevated levels of UV radiation reaching the Earth. In addition a GRB could trigger the global cooling which occurs at the end of the Ordovician period that follows an interval of relatively warm climate. Intense rapid cooling and glaciation at that time, previously identified as the probable cause of this mass extinction, may have resulted from a GRB.
The Wikipedia article that you link to discusses the possibility of the PT mass extinction being caused by a supernova within ten light years of earth. The present article, on the other hand, is about gamma-ray bursts. Not the same thing. A gamma ray burst produces something like 1e47 Joules of gamma rays (actually 1e46 Joules per steradian; we don't yet know whether bursts are focussed or otherwise directional); a supernova only produces something like 1e41 Joules per steradian of gammas (a lot more than that of neutrinos, but who cares about neutrinos).
No, stress kills.
The difference is, those stresses your body/mind is adapted to.
About to get trampled by a mastodon? Bam! Adrenaline surge, you run, condition resolved and a few hours later your body chemistry is completely normal.
But we've created a world of constant low-level stressors, where our fight, flight, or freeze reactions won't help. Stressors are unresolved, so the alert mechanism is always on at a low level, diverting resources away from the immune system and the restorative mechanism.
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