Milky Way's Black Hole a Gamma Source? 100
eldavojohn writes "A paper recently accepted for publication (preprint here) proposes a sound explanation for the source of the gamma rays that permeate our galaxy. The Milky Way's central object Sagittarius A*, widely believed to be a supermassive black hole, is now suspected to be the source. To test this theory, two scientists created a computer model to track the protons, flung outward with energies up to 100 TeV by the intense magnetic fields near the event horizon, as they make a random walk through the plasma environment. It can take thousands of years for them to travel 10 light-years from the black hole, where they collide with lower-energy protons to form pions. These decay into gamma radiation emanating from a torus-shaped region around the central object."
huh? (Score:2, Interesting)
Distribution of life? (Score:4, Interesting)
Do we know? (Score:2, Interesting)
Re:Distribution of life? (Score:5, Interesting)
Re:Distribution of life? (Score:2, Interesting)
So, maybe it is lucky it'd take about 30,000 years at the speed of light to get to the center; it is dangerous enough way out here, nevermind the comets and asteroids. 8)
Incorrect summary (Score:5, Interesting)
Re:Distribution of life? (Score:5, Interesting)
High Radiation Life Forms (Score:2, Interesting)
Re:Do we know? (Score:3, Interesting)
I suppose someone who doesn't understand the fundemental process might find dark matter and the like to seem ad hoc solutions, but when you consider that the main theory involved (General Relativity) does such an incredibly good job of modeling most of the other phenomona we see in the observable universe, it seems more reasonable to invoke something, possibly unseen, that could be playing a part, rather than tossing out an entire theory.
Re:Water Bears (Score:3, Interesting)
Hmmm, you got to wonder if that's a fortuitous coincidence or if that amazing ability to survive was spurred by something in their environment. Now that I think of it, any organism that can exist in an indefinite "cryptobiosis" [wikipedia.org] state (ie, when all metabolic processes stop for a possibly long period of time) would do better if it had some of the above properties. In particular, the ability to survive extreme genetic damage is necessary IMHO. Suppose humans had similar abilities. If I entered cryptobiosis say in an "average" North American location, I'd receive a whole body dose of perhaps 3 millisievert per year (maybe much less since I'm no longer breathing carbon 14 and radon). Since I'm in cryptobiosis, I have no ability to repair radiation damage, it's like I experience this huge pulse of radiation damage.
According to here [uic.com.au], every 100 millisievert results in a 5% boost (supposedly) in average life-time cancer rates, and 1000 or more millisievert is life threatening. So 30-40 years gives me a 5% boost in cancer rates and 300-400 years of cryptobiosis gets me up to 1000 millisievert. I can't survive roughly 3000 or more years (10 sievert which is automatically lethal) because I literally receive a fatal dose of radiation before I have a chance to repair it. We ignore that there may be other ionizing processes (chemical or thermal, for example) that would vastly shorten this time.Re:Distribution of life? (Score:3, Interesting)
This seems somewhat counter-intuitive, but if you think of a species as a set with somewhat fuzzy boundaries, more errors mean the boundaries are fuzzier. More members of a species deviate farther from the average type. Since enough members of a species usually survive long enough that the avaerage organism reproduces once, most members are already pretty well adapted to their niche. Higher mutation rates therefore mean more members are ill adapted, so selection actually slows down because more species get out of balance and die out faster and more often without leaving a successor species. A higher mutation rate also means more organisms have 2 or more mutations, and since most mutations are negative, a swamping effect occurs, where possibly good mutations don't ever get a chance to be selected. A really high mutation rate means genes don't just find themselves increasingly surrounded by defective partner genes, they actually get a chance of being overwritten before they linger for enough generations to be tested.
For sexually reproducing species, the chance of not being able to successfully breed with a given other goes up very quickly, etc, so sex becomes a less successful option than parthenogenesis, etc, and again selection slows down even more.
Most biologists think RNA was once dominant on our planet, and that there were other replicators, more primative and having higher error rates, before RNA. It's possible that some of these are more optimal under other conditions, i.e. more or less radiation, heat, or in other atmospheres. It's also possible some codes that were never developed here on Earth have developed in other places.