Julie, You might also be interested in the cover article in the March 2007 issue of Sky & Telescope ("Killer Blasts") on a related scenario of a nearby supernova being visible to proto-humans in the last few million years. Supernovae have long been known to be potential sterilizers for life within a few hundred parsecs around a detonation. Sciffy-types hypothesize that one reason E.T. hasn't contacted us is that in during the early formation of galaxies, there is more gas that creates more supernovae, effecting sterlizing the early Milky Way. Life didn't have a chance to take hold until the rate of supernovae declined. More recently, attention has turned to hypernovae that may sterilize life on kiloparsec scales. There are 3.26 light years to a parsec or about 3,200 light-years in a kiloparsec. In the last decade, there has been a great deal of research on the mysterious gamma ray bursts (GRBs) that permeate the night sky. Hypernovae are one of the suspected causes of GRBs. There are many potential causes for extinction events, for example, meteor impacts and volcanic-basaltic floods (volcanic flood fields two kilometers thick that are the size of Texas). Figuring out which cause triggered an extinction a few hundred million years after the event is a daunting challenge. It is a research area marked by heated debate. For example, although the Cretaceous extinction usually is attributed to meteor impact at the Chicxulub Crater in Mexico, but it is also associated with basaltic floods called the Deccan traps, now preserved in the Deccan Plateau in India. http://earth.jsc.nasa.gov/scripts/sseop/photo.pl?mission=STS057&roll=104&fra... Another more local example of a basaltic flood field is the Snake River plain in southern Idaho - just a few hours drive away. http://vulcan.wr.usgs.gov/Photo/NASA/AnnotatedImages/nasa_craters_moon_8410.... That volcanic flood field is the brown "u" shape above Utah that you see on the weather map on the evening news. It is the dark grey horizontal bands of rock that you see along the highway in southern Idaho as your drive to Yellowstone or Boise. The Ordovician extinction is unique in that it is the only major extinction event that is not associated with a major basaltic flood. The news story and Melott's paper are in follow-up to his original 2003 theory that GRBs may cause major extinctions, and, in particular, the Ordovician extincition about 440 million years ago. http://www.arxiv.org/abs/astro-ph/0309415 The December paper discussed in the January 2007 MSN online article - http://www.arxiv.org/abs/astro-ph/0612660 and a more recent paper in May 2007 - http://www.arxiv.org/abs/0705.4274 - are all theoretical "what if a supernovae or GRB hypernovae blows up nearby" type papers. The GRB-extinction theory is still in an early development stage. To my limited understanding, no one has ever found any kind of trace signal of a GRB in the rock record - e.g. some kind of a chemical or mineral anomaly like the increase in iridium at the Cretaceous-Tertiary boundary that marks the Chicxulub Crater impact in Mexico about 60 million years ago. In theoretical modeling in their most recent May 2007 paper, Mellot and his student Thomas, conclude that eta Carinae, which everybody agrees could blow as a super- or hyper-novae anytime between tomorrow and the next million years - is too far at about 2.5 kiloparsecs to disrupt the Earth's environment. If eta Carinae it does go it will be a good show for amateur astronomers without any bad hang-over effects on good-old Gaia. http://hubblesite.org/newscenter/archive/releases/1996/23/image/a/ With Krubrick's _Dr. Strangelove_, I stopped worrying about the bomb. I ocassionally succumb to worrying about nearby nova or supernova progenitors going off. -:) With Mellot's new modeling paper, I'm going to clean-up my meteor-watching lawn chair and go out and start routing for eta Carinae to go - well like tomorrow. -:) - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net