Difference between revisions of "Nemesis (Star)"

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−	'''Nemesis''' is a theoretical [[dwarf star]] said to orbit the sun outside of the [[Oort Cloud]]. Some scientists believe that if Nemesis exists, it's passing by the [[Oort Cloud]] might send asteroids towards Earth. This hypothesis is sometimes used to back up the belief that the dinosaurs were killed by a large asteroid or meteor impact.	+	{{Planet
		+	|name=Nemesis
		+	|image=RedDwarfAUMicroscopii.jpg
		+	|caption=A dwarf star typical of the class to which Nemesis, if it exists, would belong.
		+	|date=April 19, 1984 (proposed)<ref name=Whitmire>Whitmire, Daniel P., and Jackson, Albert A., IV. "[http://www.nature.com/nature/journal/v308/n5961/abs/308713a0.html;jsessionid=F8B0698DA58DB8138033C94BEED73B16 Are periodic mass extinctions driven by a distant solar companion]?" ''Nature'' 308:713-715, April 19, 1984. {{doi|10.1038/308713a0}} Accessed June 10, 2008</ref>
		+	|discname=Richard A. Muller<ref name=Muller>Muller, Richard A., ed. "[http://muller.lbl.gov/pages/lbl-nem.htm Nemesis]." n.d. Accessed June 10, 2008.</ref>
		+	|origname=Greek goddess of retribution<ref name=Sasha>Author unknown. "[http://swanson.bol.ucla.edu/ The Nemesis Theory]." n.d. Accessed June 10, 2008.</ref>
		+	|primary=Sun
		+	|periapsis=8,800 AU<ref name=calc>Calculated</ref>
		+	|apoapsis=167,200 AU<ref name=calc/>
		+	|semimajor=88,000 AU<ref name=Whitmire/>
		+	|eccentricity=0.9<ref name=Whitmire/>
		+	|sidereal=26,000,000 a<ref name=Whitmire/>
		+	|mass=2 * 10<sup>-4</sup> to 7 * 10<sup>-2</sup> M☉<ref name=Whitmire/>
		+	|mintemp=2300 K<ref name=Harvard>Suggested by its hypothesized spectral class of N, R, or S, consistent with its probable classification as a red or brown dwarf star. See "[http://astronomy.swin.edu.au/cosmos/H/Harvard+Spectral+Classification Harvard Spectral Classification]," ''Study Astronomy Online at Swinburne University'', accessed April 22, 2008, and Irizarry, David, "[http://www.seattleastro.org/webfoot/feb00/pg2.htm The Secrets of the Harvard Classification Revealed]," ''The Webfooted Astronomer'', Seattle Astronomical Society, February 2000, accessed April 22, 2008.</ref>
		+	|maxtemp=2600 K<ref name=Harvard/>
		+	}}'''Nemesis''' is a hypothesized and probably factitious companion [[star]] to the [[sun]]. It is said to be trans-Neptunian and to enter the [[Oort Cloud]] every 26 million Julian years. When it so enters the cloud, according to theory, it perturbs it and sends a shower of [[comet]]s into the inner [[solar system]]. A significant portion of these comets then strike the [[earth]] and cause [[extinction-level event]]s. To date no astronomer has developed definitive evidence for the existence of the Nemesis star, although two comprehensive surveys of the sky that might decide the issue are currently under way, and a third survey by a polar-orbiting rocket probe is planned.
		+	== Background of the Nemesis Hypothesis ==
		+	In 1984, [[paleontology|paleontologists]] [[David Raup]] and [[Jack Sepkoski]] published their time-series analysis of the [[geologic stratum|geologic strata]] that, according to [[uniformitarianism|uniformitarian]] geology, were laid down during the last 250 million years. They determined that twelve extinction-level events (ELEs) had occurred during this time, and that the time between one ELE and the next was 26 million years.<ref name=Raup>Raup, D. M., and Sepkowski, J. J. "[http://www.pnas.org/cgi/reprint/81/3/801.pdf Periodicity of extinctions in the geologic past]." ''Proc. Nat. Acad. Sci.'' 81(3):801-805, February 1984. {{doi|10.1073/pnas.81.3.801}}. Accessed June 10, 2008.</ref> Previous investigators had linked two of these putative ELEs to large meteorite impacts. Raup and Sepkoski therefore concluded that such events (including the alleged extinction of the [[dinosaur]]s 65 million years ago) happened regularly and might have an extraterrestrial cause.
−	{{Solarsystem}}	+	== Proposal and naming ==
		+	Two independent teams of astronomers then proposed the same type of cause: a companion star to the Sun, either a red dwarf or a brown dwarf, having a sidereal period equal to the period of Raup and Sepkoski's ELE cycle.<ref name=Whitmire/><ref name=Davis>Davis, Marc, Hut, Piet, and Muller, Richard A. "[http://www.nature.com/nature/journal/v308/n5961/abs/308715a0.html Extinction of species by periodic comet showers]." ''Nature'' 308:715-717, April 19, 1984. {{doi|10.1038/308715a0}} Accessed June 10, 2008</ref> Subsequently, Muller published a book-length treatment of the Nemesis theory.<ref name=Muller/><ref name=Mullerbook>Muller, Richard A. ''Nemesis, the Death Star: The Story of a Scientific Revolution''. Wiedenfeld and Nicolson, 1988. ASIN: B000LD03W6. Cited in Muller, Nemesis (Internet site), ''op. cit.''</ref>
−	[[category:astronomy]]	+	Muller and others named this star Nemesis after the Greek goddess of retribution.<ref name=Sasha/>
		+
		+	== Orbital characteristics ==
		+	Nemesis, if it exists, would probably be in a highly eccentric, almost parabolic orbit around the Sun. The semimajor axis would be 88,000 AU and the eccentricity 0.9.<ref name=Whitmire/> The sidereal period of 26 million years would be inferred from Raup and Sepkowski.<ref name=Raup/>
		+
		+	Muller holds that Nemesis is at or near aphelion at present and would not cause another ELE until the year 15,000,000 AD.<ref name=Davis/> Yarris<ref name=Yarris>Yarris, Lynn. "Does a Companion Star to the Sun Cause Earth's Periodic Mass Extinctions?" Science Beat. Spring 1987.</ref> has suggested that Nemesis would be visible in the [[constellation]] of Hydra.
		+
		+	== Physical characteristics ==
		+	Whitmire and Jackson have suggested that Nemesis would have a mass varying from 2 * 10<sup>−4</sup> to 7 * 10<sup>−2</sup> times the mass of the sun. This is the range of masses of brown or black dwarf stars. Muller has argued that the star is a somewhat hotter red dwarf, of magnitude between 7 and 12.<ref name=Muller/>
		+
		+	== Controversy ==
		+	Nemesis has been a subject of heated controversy ever since the publication of the papers by Whitmire and Jackson, and Davis, Hut, and Muller.<ref name=Britt>Britt, Robert Roy. "[http://www.space.com/scienceastronomy/solarsystem/nemesis_010320-1.html Nemesis: Does the Sun Have a Companion]?" <http://space.com/>, April 3, 2001. Accessed June 10, 2008.</ref><ref name=ExitMundi>Author unknown. "[http://www.exitmundi.nl/Nemesis.htm Er...Is That Really a Second Sun Up There]?" n.d. Accessed June 10, 2008.</ref><ref name=Schlyter>Schlyter, Paul. "[http://www.nineplanets.org/hypo.html#nemesis Nemesis, the Companion Star]," in "Hypothetical Planets." ''The <s>Nine</s> 8 Planets'', Bill Arnett, ed. February 14, 2006. Accessed June 10, 2008.</ref><ref name=Mukai>Mukai, Koji, and Christian, Eric. "[http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961130b1.html The Nemesis Star]." ''Ask an Astrophysicist'', Imagine the Universe!, [[National Aeronautics and Space Administration|NASA]], December 1, 2005. Accessed June 10, 2008.</ref>  Muller has perhaps compounded the controversy by asserting<ref name=Muller/> that Nemesis would be visible with binocular field glasses or a small to medium-sized telescope. No astronomer, amateur or professional, has even claimed to have seen Nemesis, much less had a sighting confirmed.<ref name=ExitMundi/><ref name=Schlyter/>
		+
		+	Muller has suggested that the Moon suffered a bombardment event as recently (per uniformitarian theories) as 400 to 600 million years ago, and that Nemesis might have been the cause.<ref name=MullerMoon>Muller, Richard A. "[http://muller.lbl.gov/papers/Lunar_impacts_Nemesis.pdf 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). Accessed June 10, 2008.</ref> Yet no geologist has developed evidence for periodic bombardment of the Moon, in line with the alleged 12 ELEs on the earth.
		+
		+	The orbit of Nemesis would be unstable, and many astronomers hold that Nemesis should long ago have escaped the Sun's gravity. Muller disputes these claims and insists that Nemesis ought to remain a part of the solar system for another billion years.<ref name=Muller/>
		+
		+	Recently, Walter Cruttenden at the Binary Research Institute has decided that [[Sedna]], a [[scatter disk]] object, actually is in orbital resonance with Nemesis.<ref name=Cruttenden>Staff. "[http://www.spacedaily.com/reports/Evidence_Mounts_For_Companion_Star_To_Our_Sun.html Evidence Mounts For Companion Star To Our Sun]." ''SpaceDaily'', April 25, 2006. Accessed June 10, 2008.</ref> Sedna's sidereal year is estimated to be 12,000 Earth years. If Sedna is in resonance with Nemesis, then it would probably have an actual period of 13,000 years and be in a 20:1 resonance with the hypothetical star.
		+
		+	However, even uniformitarian geologists do not necessarily accept the claimed periodicity of ELEs.<ref name=Britt/><ref name=Mukai/>
		+
		+	=== Re-examination ===
		+	On 2 July 2010, Mellot and Barnbach published a study suggesting that the ELEs have occurred over 500 million years, during which galactic tides and encounters with passing stars should have perturbed the orbit of the hypothetical Nemesis, but did not. Therefore, they now say, such a star cannot be blamed for ELEs occurring regularly ever 26 million years.<ref name=Mellot>Mellot A and Barnbach RK, "Nemesis reconsidered", ''Solar and Stellar Astrophysics'', 2 July 2010. Accesssed 12 July 2010. {{arXiv|1007.0437v1}}</ref>
		+
		+	== A creationist perspective ==
		+	The Nemesis hypothesis depends on uniformitarian geology, and in particular the acceptance of [[deep time]]. If, instead, one accepts the model of the [[Great Flood]], then one has no need of a theory of a companion star (or, for that matter, a cloud of comets for the star to dive into). The alleged regular layers of extinct species could all result from laminar flow patterns during the Flood.
		+
		+	== Search for Nemesis ==
		+	As mentioned, no one has yet seen Nemesis. A recent infrared survey of the sky failed to detect it.<ref name=Schlyter/> But at least two more wide-ranging surveys of the sky are planned, by the Panoramic Survey Telescope and Rapid Response System (Pan-Starrs)<ref name=PanStarrs>"[http://pan-starrs.ifa.hawaii.edu/public/ Pan-Starrs Home]."</ref> and the Large Synoptic Survey Telescope (LSST)<ref name=Muller/><ref name=LSST>"[http://www.lsst.org/lsst_home.shtml LSST Home]."</ref>
		+
		+	== References ==
		+	{{reflist|2}}
		+	== Related Link ==
		+	* Muller, Richard A. "[https://www.youtube.com/watch?v=ERy-MTfgulc Physics 10 - Lecture 25: Universe II]" Department of Physics, [[University of California]], [[Berkeley]], [[California]], delivered May 4, 2006. Mentions Nemesis ''inter alia''.
		+
		+	== See also ==
		+	* [[Oort Cloud]]
		+	{{Solarsystem}}
		+	[[Category:Astronomy]]

---

Latest revision as of 18:44, September 26, 2018

Nemesis
A dwarf star typical of the class to which Nemesis, if it exists, would belong.
Date of discovery	April 19, 1984 (proposed)[1]
Name of discoverer	Richard A. Muller[2]
Name origin	Greek goddess of retribution[3]
Orbital characteristics
Primary	Sun
Perihelion	8,800 AU[4]
Aphelion	167,200 AU[4]
Semi-major axis	88,000 AU[1]
Orbital eccentricity	0.9[1]
Sidereal year	26,000,000 a[1]
Physical characteristics
Mass	2 * 10-4 to 7 * 10-2 M☉[1]
Minimum temperature	2300 K[5]
Maximum temperature	2600 K[5]

Nemesis is a hypothesized and probably factitious companion star to the sun. It is said to be trans-Neptunian and to enter the Oort Cloud every 26 million Julian years. When it so enters the cloud, according to theory, it perturbs it and sends a shower of comets into the inner solar system. A significant portion of these comets then strike the earth and cause extinction-level events. To date no astronomer has developed definitive evidence for the existence of the Nemesis star, although two comprehensive surveys of the sky that might decide the issue are currently under way, and a third survey by a polar-orbiting rocket probe is planned.

Background of the Nemesis Hypothesis

In 1984, paleontologists David Raup and Jack Sepkoski published their time-series analysis of the geologic strata that, according to uniformitarian geology, were laid down during the last 250 million years. They determined that twelve extinction-level events (ELEs) had occurred during this time, and that the time between one ELE and the next was 26 million years.^[6] Previous investigators had linked two of these putative ELEs to large meteorite impacts. Raup and Sepkoski therefore concluded that such events (including the alleged extinction of the dinosaurs 65 million years ago) happened regularly and might have an extraterrestrial cause.

Proposal and naming

Two independent teams of astronomers then proposed the same type of cause: a companion star to the Sun, either a red dwarf or a brown dwarf, having a sidereal period equal to the period of Raup and Sepkoski's ELE cycle.^[1][7] Subsequently, Muller published a book-length treatment of the Nemesis theory.^[2][8]

Muller and others named this star Nemesis after the Greek goddess of retribution.^[3]

Orbital characteristics

Nemesis, if it exists, would probably be in a highly eccentric, almost parabolic orbit around the Sun. The semimajor axis would be 88,000 AU and the eccentricity 0.9.^[1] The sidereal period of 26 million years would be inferred from Raup and Sepkowski.^[6]

Muller holds that Nemesis is at or near aphelion at present and would not cause another ELE until the year 15,000,000 AD.^[7] Yarris^[9] has suggested that Nemesis would be visible in the constellation of Hydra.

Physical characteristics

Whitmire and Jackson have suggested that Nemesis would have a mass varying from 2 * 10⁻⁴ to 7 * 10⁻² times the mass of the sun. This is the range of masses of brown or black dwarf stars. Muller has argued that the star is a somewhat hotter red dwarf, of magnitude between 7 and 12.^[2]

Controversy

Nemesis has been a subject of heated controversy ever since the publication of the papers by Whitmire and Jackson, and Davis, Hut, and Muller.^{[10][11][12][13]} Muller has perhaps compounded the controversy by asserting^[2] that Nemesis would be visible with binocular field glasses or a small to medium-sized telescope. No astronomer, amateur or professional, has even claimed to have seen Nemesis, much less had a sighting confirmed.^[11][12]

Muller has suggested that the Moon suffered a bombardment event as recently (per uniformitarian theories) as 400 to 600 million years ago, and that Nemesis might have been the cause.^[14] Yet no geologist has developed evidence for periodic bombardment of the Moon, in line with the alleged 12 ELEs on the earth.

The orbit of Nemesis would be unstable, and many astronomers hold that Nemesis should long ago have escaped the Sun's gravity. Muller disputes these claims and insists that Nemesis ought to remain a part of the solar system for another billion years.^[2]

Recently, Walter Cruttenden at the Binary Research Institute has decided that Sedna, a scatter disk object, actually is in orbital resonance with Nemesis.^[15] Sedna's sidereal year is estimated to be 12,000 Earth years. If Sedna is in resonance with Nemesis, then it would probably have an actual period of 13,000 years and be in a 20:1 resonance with the hypothetical star.

However, even uniformitarian geologists do not necessarily accept the claimed periodicity of ELEs.^[10][13]

Re-examination

On 2 July 2010, Mellot and Barnbach published a study suggesting that the ELEs have occurred over 500 million years, during which galactic tides and encounters with passing stars should have perturbed the orbit of the hypothetical Nemesis, but did not. Therefore, they now say, such a star cannot be blamed for ELEs occurring regularly ever 26 million years.^[16]

A creationist perspective

The Nemesis hypothesis depends on uniformitarian geology, and in particular the acceptance of deep time. If, instead, one accepts the model of the Great Flood, then one has no need of a theory of a companion star (or, for that matter, a cloud of comets for the star to dive into). The alleged regular layers of extinct species could all result from laminar flow patterns during the Flood.

Search for Nemesis

As mentioned, no one has yet seen Nemesis. A recent infrared survey of the sky failed to detect it.^[12] But at least two more wide-ranging surveys of the sky are planned, by the Panoramic Survey Telescope and Rapid Response System (Pan-Starrs)^[17] and the Large Synoptic Survey Telescope (LSST)^[2][18]

References

Related Link

• Muller, Richard A. "Physics 10 - Lecture 25: Universe II" Department of Physics, University of California, Berkeley, California, delivered May 4, 2006. Mentions Nemesis inter alia.

See also

• Oort Cloud

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