[meteorite-list] Nemesis-The Death Star

From: Shawn Alan <photophlow_at_meteoritecentral.com>
Date: Sat, 13 Mar 2010 20:04:05 -0800 (PST)
Message-ID: <548573.69746.qm_at_web113613.mail.gq1.yahoo.com>

Hello List,

Last week a good topic was brought about the probability of patterns with the places and amount of meteorites coming in contact with Earth. I am not sure if this hypothesis was suggested but I came across the Nemesis Hypothetical red dwarf star hypotheses in Rocks from Space by O.Richard Norton and Wikipedia. Here is what is on Wikipedia?..

Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. This star was originally postulated to exist as part of a hypothesis to explain a perceived cycle of mass extinctions in the geological record, which seem to occur once every 26 million years or so.

Claimed periodicity of mass extinctions

In 1984, paleontologists David Raup and Jack Sepkoski published a paper claiming that they had identified a statistical periodicity in extinction rates over the last 250 million years using various forms of time series analysis.[1] They focused on the extinction intensity of fossil families of marine vertebrates, invertebrates, and protozoans, identifying 12 extinction events over the time period in question. The average time interval between extinction events was determined as 26 million years. At the time, two of the identified extinction events (Cretaceous-Tertiary and Late Eocene) could be shown to coincide with large impact events. Although Raup and Sepkoski could not identify the cause of their supposed periodicity, they suggested that there might be a non-terrestrial connection. The challenge to propose a mechanism was quickly addressed by several teams of astronomers.
 
Development of the Nemesis hypotheses

Two teams of astronomers, Whitmire and Jackson, and Davis, Hut, and Muller, independently published similar hypotheses to explain Raup and Sepkoski's extinction periodicity in the same issue of the journal Nature.[2][3] This hypothesis proposes that the sun may have an as yet undetected companion star in a highly elliptical orbit that periodically disturbs comets in the Oort cloud, causing a large increase in the number of comets visiting the inner solar system with a consequential increase in impact events on Earth. This became known as the Nemesis (or, more colorfully, Death Star) hypothesis.

If it does exist, the exact nature of Nemesis is uncertain. Richard A. Muller suggests that the most likely object is a red dwarf with magnitude between 7 and 12,[4] while Daniel P. Whitmire and Albert A. Jackson argue for a brown dwarf. If a red dwarf, it would undoubtedly already exist in star catalogs, but its true nature would only be detectable by measuring its parallax; due to orbiting the Sun it would have a very low proper motion and would escape detection by proper motion surveys that have found stars like the 9th magnitude Barnard's star.

The last major extinction event was about 5 million years ago, so Muller posits that Nemesis is likely 1 to 1.5 light years away at present, and even has ideas of what area of the sky it might be in (supported by Yarris, 1987), near Hydra, based on a hypothetical orbit derived from original apogees of a number of atypical long-period comets that describe an orbital arc meeting the specifications of Muller's hypothesis.

Looking for Nemesis

If Nemesis exists, then it may be detected by the planned Pan-STARRS or LSST astronomical surveys.
In particular, if Nemesis is a brown dwarf, then the WISE mission should be able to find it. The hypothesis that the Nemesis star is a brown dwarf was proposed by Dan Whitmire and Albert A. Jackson, IV.[5]

Also, if you own a copy of Rocks from Space I would look towards the back of the book and read up on Nemesis. It is a very good hypothesis and makes since that this could be taking place in our solar system.
Received on Sat 13 Mar 2010 11:04:05 PM PST