Dynamical constraints on the mass and perihelion distance of Nemesis and the stability of its orbit

  title={Dynamical constraints on the mass and perihelion distance of Nemesis and the stability of its orbit},
  author={JACK G. Hills},
  • J. Hills
  • Published 1 October 1984
  • Physics, Geology
  • Nature
It has been suggested1,2 that the observed periodic extinction of species at intervals of 26 Myr (ref. 3) may be catalysed by a hypothetical stellar companion of the Sun, Nemesis, with an orbital period of 26 Myr. The passage of a stellar companion through the inner comet cloud4 will fill the loss cone of these comets and cause a comet shower to enter the planetary system. It has been estimated that about 20–30 comets will hit the Earth during a shower, which lasts less than a million yr. Such… 
Periodic comet showers and planet X
The discovery1 that Pluto's mass is insufficient to explain the discrepancies in the motions of the outer planets has led to the prediction of a tenth planet (planet X) of mass ∼1–5 M⊕ beyond the
Constraints on the location of a putative distant massive body in the Solar System from recent planetary data
We analytically work out the long-term variations caused on the motion of a planet orbiting a star by a very distant, pointlike massive object X. Apart from the semi-major axis a, all the other
The planet nine hypothesis
The great escape - III. Placing post-main-sequence evolution of planetary and binary systems in a Galactic context
Our improving understanding of the life cycle of planetary systems prompts investigations of the role of the Galenvironment before, during and after asymptotic giant branch (AGB) stellar evolution.
Planet X — The current status
Neptune and Pluto were discovered because of predictions derived from the differences between the observations and ephemerides of Uranus, but Pluto wasn't the predicted planet and the discrepancies
Nemesis reconsidered: Nemesis reconsidered
This work examines the evidence for the previously proposed periodicity of a companion object orbiting the Sun, using two modern, greatly improved paleontological datasets of fossil biodiversity, and finds that there is a narrow peak at 27 My in the cross-spectrum of extinction intensity time series between these independent datasets.


Extinction of species by periodic comet showers
A 26-Myr periodicity has recently been seen in the fossil record of extinction in the geological past1. At least two of these extinctions are known to be associated with the impact on the Earth of a
Are periodic mass extinctions driven by a distant solar companion?
Raup and Sepkoski1–3 have recently reported evidence for a 26-Myr cycle in biological mass extinctions which, if real, requires an astronomical explanation. Here we investigate a model in which this
Comet showers and the steady-state infall of comets from the Oort cloud
The appearance of an inner edge to the Oort comet cloud at a semimajor axis of a = (1--2) x 10/sup 4/ AU is an observational artifact. Stellar perturbations are frequent enough and strong enough to
The Formation of Comets by Radiation Pressure in the Outer Protosun. III. Dependence on the Anisotropy of the Radiation Field
A two-dimensional, radiation-hydrodynamic code with dust was used to study the effect of an anisotropic radiation field on the formation of comets in the outer protosun by the radiation pressure from
Effect of low-velocity, low-mass intruders (collisionless gas) on the dynamical evolution of a binary system
More than 20,000 computer-simulated encounters between low-mass (compared to the binary components) intruders and binary systems have been made. These calculations were made in the important (and
The formation of comets by radiation pressure in the outer protosun
The pressure due to the radiation from the Sun and neighboring protostars may have forced the coagulation into comets of the dust grains in the collapsing layers of the protosun at r = (1-5) x 10/sup
Dynamic Relaxation of Planetary Systems and Bode's Law
That an epoch characterized by strong dynamical encounters occurred before the planets relaxed into stable orbits is suggested by the surprisingly large differences between the inclinations of their angular momentum vectors of rotation and those of orbital revolution.
Long-term captures of low-mass intruders by binary stars
Intensive computer simulations were made of three families of encounters between a binary star and a low-mass intruder which previous work indicated have a high probability of producing long-lived
Periodicity of extinctions in the geologic past.
  • D. Raup, J. Sepkoski
  • Geography, Environmental Science
    Proceedings of the National Academy of Sciences of the United States of America
  • 1984
The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis and contains 12 extinction events that show a statistically significant periodicity.