Re: [meteorite-list] Cyclic mass extinction?

[TMS/TNS/HRC]

I must be more organized than I thought!  Found the book smushed between a biography of Alexander the Great and "How to Clean Just About Anything".  OK, maybe I'm not that organized....but I did find it!  : )   NEMESIS The Death-Star and Other Theories of Mass Extinction by Donald Goldsmith, copyright 1985 (I've dated myself!!!) and published by Berkley Books, NY.   A blurb: "(The Nemesis theory) relies on an entirely unknown object to cause the (cometary) perturbations. Hence, the theory can assign the Nemesis star the most effective orbit to produce the observed results, which the Nemesis theorists insist is a period close to 26 million years in the extinction rate, and close to 28.4 million years in the impact crater record.... Skeptics say the Nemesis Theory requires that the sun be a member of an unusual star system, a double-star system in which a low mass companion moves in an extremely large orbit around the system's center of mass, which would be close to the much more massive star in the system, our sun.  Such a double star system would be unlike almost all the stars and star systems we observe around us. (snip)   Nemesis would have to move in a highly, but not tremendously elongated orbit, one in which its distance from the sun falls to a minimum of 26,000 A.U. and increases to a maximum of 150,000 A.U....Since the force of gravity increases in proportion to one over the square of the distance between two objects, Nemesis at its close approaches to the sun would have a far stronger effect on comets in the Oort cloud, most of which are from 10,000 to 40,000 A.U. from the sun, than it would at its average distance (88,000 A.U.) let alone at its maximum distances from the sun."   It goes on to talk more about the theorists, and the theoretical orbit, mass and luminosity of Nemesis.  If anyone would like more information on anything regarding this, let me know and I'll look it up.   Off to bed, Jeannie     ----- Original Message ----- From: Edward R. Hodges To: [EMAIL PROTECTED] Sent: Wednesday, July 24, 2002 10:58 PM Subject: [meteorite-list] Cyclic mass extinction?     I happened to catch the last few minutes of a show on PBS about extinction. One of the scientist had compiled data on thousands of extinct species and graphed the times of their extinction. In the timeline he created there seemed to be above normal rates of mass extinction every 26 million years. Another scientist is working on a theory that the sun has a companion star, "Nemesis" that perturbs the orbit of comets in the Oort cloud which impact the Earth roughly every 26 million years. Who can shed some light on this topic? Wouldn't there be clear evidence of meteoritic dust fallout in clay deposits in strata spanning every 26my? Interesting, very interesting. Didn't catch the name of the show, or the names of the scientists.- Edward   Edward R. Hodges www.meteoriteonline.com IMCA#4173