December 31, 2012 – SPACE - Large sun-grazing comets could bring on the sort of global electronics meltdown usually associated with electromagnetic pulse weapons or a full-scale nuclear exchange. Or so says David Eichler, lead author of a forthcoming Astrophysical Journal Letters paper positing that a sun-grazing comet roughly the size of Hale-Bopp (with a nucleus some 30 kms in diameter), could trigger cosmic ray-generating shockwaves large enough to initiate a global electromagnetic Armageddon. Eichler, an astrophysicist at Israel’s Ben-Gurion University of the Negev in Beer-Sheva, argues that satellites that weren’t in protection mode would be wiped out along with most of the world’s electronics — everything from micro-circuitry on cell phones to full-scale power stations. If such a comet were the size of Hale-Bopp, Eichler says, the resulting solar flare would by far be the largest ever observed. The comet gets compressed and then explodes in the solar atmosphere which, in turn, creates shockwaves, says Eichler. Eichler thinks that such a sun-grazing comet may have triggered a large solar flare and cosmic ray-generating shockwaves as recently as 775 A.D., as indicated by tree ring analysis pointing to a sudden 1.2 percent spike in atmospheric Carbon 14. “I’m not saying that [event] couldn’t have been caused by a magnetic solar flare, but we’ve never seen a solar flare nearly that big,” said Eichler. Although the motion of such a sun-grazer would be the source of the shock waves’ energy, the actual particle acceleration would happen within the sun’s magnetic field, explains Eichler. Traveling at a 1000 kms per second, the shockwaves would reach earth in about a day and a half. And the effects would likely be much worse than the 1859 Carrington Event, a solar super-storm that wreaked havoc on telegraph lines and caused the aurora borealis to be visible as far south as Texas. A recent exception was Comet Lovejoy, a long period sun-grazing comet which in December 2011, was observed to unexpectedly survive its closest solar approach. Eichler says it’s quite possible that a very large comet could graze the sun once every several thousand years. “If the Hale-Bopp-sized comet grazed the solar corona,” said Eichler, “then you’d get a much bigger solar flare than the Carrington Event. Hale-Bopp itself may become sun-grazing in the [distant] future.” But there is one positive. Astronomers should, in principle, get a few years notice if such a large potential sun-grazing comet comes around again. However, with a few classified military exceptions, our electronics remain unprotected against such potential magnetospheric trauma, he says. Today, the Carrington Event itself would be devastating, says Eichler, and it wasn’t particularly powerful or all that unusual on an astrophysical timescale. After completing his research, Eichler says he is most surprised by the fact that we’re still here to tell the tale. “I didn’t realize the solar system was such a dangerous place,” said Eichler. “Just the fact that we’ve gone as long as we have without worse things happening may be why we’re here.” –Forbes
Orbital diagram and current position of Comet C/2012 S1 (ISON). The comet is at approx. magnitude 18 and located about 6.25 AU from the Sun. Could this brighten into one of the brightest comets ever? It’s possible. It is possible that this comet could develop a spectacular tail or briefly approach the brightness of the full Moon toward the end of 2013. Alternatively, the comet could break up when it gets closer to the Sun. The comet was discovered by Russian scientists Vitali Nevski (Belarus) and Artyom Novichonok (Russia). It is currently approaching the Sun from between the orbits of Jupiter and Saturn. Comet ISON appears on course to achieve sungrazer status as it passes within a solar diameter of Sun’s surface in November 2013. Whatever survives will then pass nearest the Earth in late December 2013. Astronomers around the world will be closely tracking this large snowball to better understand its nature and how it might evolve during the next 15 months. (Image Credit: JPL)
