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Encyclopedia > Nemesis (star)

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. Richard A. Muller suggests that the most likely object is a red dwarf with magnitude between 7 and 12 [1], while Whitmire and Jackson argue for a brown dwarf. Such a bright red dwarf would undoubtedly already be in existing 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. This article is about red dwarfs, the type of star. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... The Sun is the star at the center of Earths solar system. ... To help compare different distances this page lists lengths starting at 1015 m (1,000,000 million km). ... To help compare different distances this page lists lengths starting at 1016 m (67,000 AU, 1. ... The astronomical unit (AU or au or a. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Richard A. Muller(Born January 6, 1944) of San Francisco, California, USA, is a physicist who works at the University of California, Berkeley and Lawrence Berkeley National Laboratory. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ... Parallax (Greek: παραλλαγή (parallagé) = alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, due to the motion of an observer. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... Barnards star is a star in the constellation Ophiuchus which is notable for having the largest proper motion (10. ...

Contents


History of the hypotheses

Nemesis' existence was proposed by Whitmire and Jackson in Nature in 1984, 308, 713-715, and also by Davis, Hut & Muller in 1984 (Nature 308 : 715-717) to explain an apparent 26-million year cycle in the occurrence of mass extinctions on Earth as noted by Raup and Sepkoski. In Whitmire and Jackson's model Nemesis is a brown dwarf while in the model of Davis et al. Nemesis is assumed to be a normal M type star. An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... J. John Sepkoski Jr. ...


According to the theory, Nemesis periodically (roughly every 26 million years), passes through a denser region of the Oort cloud, disrupting the orbits of comets, and sending millions of comets into the inner solar system and potential collision with the Earth. The last major extinction period was about 5 million years ago, so Muller posits that Nemesis is likely 1-1.5 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 theoretical orbit derived from original apogees of a number of atypical long period comets that describe an orbital arc that meets the specifications of Muller's theory. It was initially nicknamed the "death star", after the fictional Star Wars weapon, although this nickname has fallen out of usage. This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Comet Hale-Bopp For other uses, see Comet (disambiguation). ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... The original Death Star The Death Star was a giant military battle station in the fictional Star Wars universe. ... The cover of the 2004 DVD widescreen release of the modified original Star Wars Trilogy. ...


No direct proof of the existence of Nemesis has been found, however, and the existence of a periodicity in the Earth's series of mass extinctions is disputed. Muller has proposed that, based on analysis of lunar rocks that indicate the impact history of the Moon, a major uptick in lunar impacts 400 million years ago (mya) represents a major shift in the orbit of Nemesis into its present rather eccentric orbit, which according to Piet Hut will only be stable for another billion years.


Matese and Whitman have suggested that the cycle might be caused by the solar system oscillating across the galactic plane. These oscillations may lead to gravitational disturbances in the Oort cloud with the same proposed consequences as the orbit of "Nemesis". However, the period of oscillation is not well-constrained observationally, and may differ from the needed 26 million years by as much as 40%. Note: This article contains special characters. ...


If Nemesis exists, it may be detected by the planned Pan-STARRS or LSST astronomical surveys, or similar future projects. If Nemesis is a brown dwarf as proposed by Whitmire and Jackson then the upcoming WISE mission should easily find it. Pan-STARRS logo Pan-STARRS (an acronym for Panoramic Survey Telescope and Rapid Response System) is a planned astronomical survey that will conduct astrometry and photometry of much of the entire sky on a continuous basis. ... The LSST. The Large Synoptic Survey Telescope is a proposed wide-field survey telescope that will cover the available sky every three nights. ...


References

  • Whitmire, D. and Jackson, A. "Are periodic mass extinctions driven by a distant solar companion?", Nature, 308, 713 (1984).
  • Richard A. Muller, Nemesis (undated)
  • Richard A. Muller, Measurement of the lunar impact record for the past 3.5 billion years, and implications for the Nemesis theory, Geological Society of America Special Paper 356, pp 659-665 (2002).I
  • Robert Roy Britt, Nemesis: Does the Sun Have a 'Companion'?, Space.com, 3 April 2001.
  • Z.K. Silagadze, TeV scale gravity, mirror universe, and ... dinosaurs, Acta Physica Polonica B32 (2001) 99-128. (Provides a very entertaining and readable review of the Nemesis extinction hypothesis, including dozens of references to scientific articles on the topic.)
  • (no author), Exit Mundi, (undated). (Nemesis an End-Of-World scenario.)
  • R. Foot, Z. K. Silagadze, Do mirror planets exist in our solar system? Acta Physica Polononica B32 (2001) pp. 2271-2278.
  • Yarris, Lynn. "Does a Companion Star to the Sun Cause Earth's Periodic Mass Extinctions?" Science Beat. Spring 1987

See also

The end of civilization or the end of the world are phrases used in reference to human extinction scenarios, doomsday events, and related hazards which occur on a global scale. ... Nemesis is a science fiction novel by Isaac Asimov. ... Dr. Isaac Asimov (c. ...

Internal links

90377 Sedna is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. ... Ever since the discovery of Pluto, the existence of a tenth planet has been speculated by astronomers and the general public alike. ...

External links


  Results from FactBites:
 
Nemesis (star) - Wikipedia, the free encyclopedia (496 words)
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.
Nemesis' existence was proposed by Whitmire and Jackson in Nature in 1984, 308, 713-715, and also by Davis, Hut and Muller in 1984 (Nature 308 : 715-717) to explain an apparent 26-million year cycle in the occurrence of mass extinctions on Earth as noted by Raup and Sepkoski.
According to the theory, Nemesis periodically (roughly every 26 million years), passes through a denser region of the Oort cloud, disrupting the orbits of comets, and sending millions of comets into the inner solar system and potential collision with the Earth.
Nemesis (star) - definition of Nemesis (star) in Encyclopedia (162 words)
Nemesis is the name given to a theoretical companion star or brown dwarf orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud.
Nemesis' existence was proposed in a theory put forward by Richard A. Muller to explain an apparent 26-million year cycle in the occurrence of mass extinctions on Earth noted by Raup and Sepkoski.
According to the theory, Nemesis periodically (roughly every 26 million years), passes through a denser region of the Oort cloud, disrupting the orbits of comets, and sending millions into the inner solar system and potential collision with the Earth.
  More results at FactBites »

 
 

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