Extinction of species by periodic comet showers

  title={Extinction of species by periodic comet showers},
  author={Marc Davis and Piet Hut and Richard A. Muller},
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 comet or asteroid with a diameter of a few kilometres (refs 2, 3). We propose that the periodic events are triggered by an unseen companion to the Sun, travelling in a moderately eccentric orbit, which at its closest approach (perihelion) passes through the ‘Oort cloud’ of comets which surrounds the… 

Orbital stability of the unseen solar companion linked to periodic extinction events

Recent suggestions of astronomical causes for the closely periodic extinction events in the geological record1 and the possible periodicities in the cratering record2 have involved two basic ideas.

How stable is an astronomical clock that can trigger mass extinctions on Earth?

  • P. Hut
  • Physics, Geology
  • 1984
The periodicity in mass extinctions observed in the fossil record1,2 may be driven by an astronomical clock consisting of a companion star to the Sun3,4. Each perihelion passage of the companion star

Cometary showers and unseen solar companions

The possibility that an invisible solar companion passing through the Oort cloud every 28 Myr precipitates a sufficiently high rate of cometary collisions with the earth to account for periodic mass

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

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

Evidence from crater ages for periodic impacts on the Earth

Recent evidence has indicated that the impact of a comet or asteroid may have been responsible for mass extinction at the ends of both the Cretaceous1 and the Eocene2–4. Quantitative analysis by Raup

Terrestrial impactors at geological boundary events: comets or asteroids?

Evidence has been presented1,2 for a 26–28-Myr periodicity in both the terrestrial extinction record and the age of large well-dated impact craters on the Earth. A cometary source controlled by

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

Cometary impacts, molecular clouds, and the motion of the Sun perpendicular to the galactic plane

Raup and Sepkoski1 have presented evidence from marine fossils for a 26-Myr periodicity in the occurrence of mass extinctions. Using the same data Rampino and Stothers2 obtained a different period,

Terrestrial catastrophism—Nemesis or Galaxy?

The ∼30 Myr periodicity associated with the Sun's motion through the central plane has been linked to geomagnetic reversals1,2, biological extinctions3 and crater ages4–6. This periodicity is

Statistical and Evolutionary Aspects of Cometary Orbits

The observed frequency of passages of Earth-crossing long-period (LP) comets (P > 200 yr) is about three per year for comets brighter than absolute magnitude H10 ~ 10.5. About one out of six LP



Evidence from crater ages for periodic impacts on the Earth

Recent evidence has indicated that the impact of a comet or asteroid may have been responsible for mass extinction at the ends of both the Cretaceous1 and the Eocene2–4. Quantitative analysis by Raup

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


Two classes of solid bodies large enough to be detected by telescopes occur in orbits that overlap that of the Earth. These bodies are the Earth-crossing asteroids and comet nuclei. Although their

Extraterrestrial Cause for the Cretaceous-Tertiary Extinction

A hypothesis is suggested which accounts for the extinctions and the iridium observations, and the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other.

Has the Sun really got a companion star?

HARRISON1 has pointed out that the six radio pulsars with the smallest observed spin-down rates (\Ṗ) are grouped together in a relatively small region of the sky, roughly in the direction of

Periodicity of Extinctions in the Geologic Past :

The probability of extinction has decreased uniformly over Phanerozoic time the use of ARIMA time-series models, whereas the inertia or stability of the biotic system after the Late Permian crisis has been obtained and displays peri-increased.

Iridium Anomaly Approximately Synchronous with Terminal Eocene Extinctions

The iridium anomaly and the tektites and microtektites are supportive of a major bolide impact about 34 million years ago, and other workers have deduced that the microtekkites are part of the North American strewn tektite field, which is dated at about34 million years before present.

Experimental evidence that an asteroid impact led to the extinction of many species 65 million years ago.

  • L. W. Alvarez
  • Geology, Physics
    Proceedings of the National Academy of Sciences of the United States of America
  • 1983
An overview is presented of the theory that an asteroid hit the earth 65 million years ago wiping out large numbers of land and marine species, and the transport mechanism of the dust created by the impact and four mechanisms for the extinction of species are discussed.

The Nearby Stars

Before turning to the nearest stars, we shall first make another survey. From the observational point of view the very brightest stars offer obvious advantages. However, apparent brightness is not a