Hostname: page-component-78c5997874-j824f Total loading time: 0 Render date: 2024-11-18T13:14:36.800Z Has data issue: false hasContentIssue false

Jupiter – friend or foe? II: the Centaurs

Published online by Cambridge University Press:  24 December 2008

J. Horner*
Affiliation:
Astronomy Group, Physics & Astronomy, The Open University, Milton KeynesMK7 6AA, UK
B.W. Jones
Affiliation:
Astronomy Group, Physics & Astronomy, The Open University, Milton KeynesMK7 6AA, UK

Abstract

It has long been assumed that the planet Jupiter acts as a giant shield, significantly lowering the impact rate of minor bodies upon the Earth, and thus enabling the development and evolution of life in a collisional environment which is not overly hostile. In other words, it is thought that, thanks to Jupiter, mass extinctions have been sufficiently infrequent that the biosphere has been able to diversify and prosper. However, in the past, little work has been carried out to examine the validity of this idea. In the second of a series of papers, we examine the degree to which the impact risk resulting from objects on Centaur-like orbits is affected by the presence of a giant planet, in an attempt to fully understand the impact regime under which life on Earth has developed. The Centaurs are a population of ice-rich bodies which move on dynamically unstable orbits in the outer Solar system. The largest Centaurs known are several hundred kilometres in diameter, and it is certain that a great number of kilometre or sub-kilometre sized Centaurs still await discovery. These objects move on orbits which bring them closer to the Sun than Neptune, although they remain beyond the orbit of Jupiter at all times, and have their origins in the vast reservoir of debris known as the Edgeworth–Kuiper belt that extends beyond Neptune. Over time, the giant planets perturb the Centaurs, sending a significant fraction into the inner Solar System where they become visible as short-period comets. In this work, we obtain results which show that the presence of a giant planet can act to significantly change the impact rate of short-period comets on the Earth, and that such planets often actually increase the impact flux greatly over that which would be expected were a giant planet not present.

Type
Research Article
Copyright
Copyright © 2008 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Babadzhanov, P.B., Wu, Z., Williams, I.P. & Hughes, D.W. (1991). The Leonids, Comet Biela and Biela's associated meteor stream. Mon. Not. R. Astron. Soc. 253, 6974.CrossRefGoogle Scholar
Chambers, J.E. (1999). A hybrid symplectic integrator that permits close encounters between massive bodies. Mon. Not. R. Astron. Soc. 304, 793799.CrossRefGoogle Scholar
Chapman, C.R. & Morrison, D. (1994). Impacts on the Earth by asteroids and comets: assessing the hazard. Nature 367, 3340.CrossRefGoogle Scholar
Greaves, J.S. (2006). Persistent hazardous environments around stars older than the Sun. Int. J. Astrobiology 5, 187190.CrossRefGoogle Scholar
Gomes, R., Levison, H.F., Tsiganis, K. & Morbidelli, A. (2005). Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Nature 435, 466469.CrossRefGoogle ScholarPubMed
Horner, J., Evans, N.W. & Bailey, M.E. (2004). Simulations of the population of Centaurs – I. The bulk statistics. Mon. Not. R. Astron. Soc. 354, 798810.CrossRefGoogle Scholar
Horner, J., Evans, N.W., Bailey, M.E. & Asher, D.J. (2003). The populations of comet-like bodies in the Solar system. Mon. Not. R. Astron. Soc. 343, 10571066.CrossRefGoogle Scholar
Horner, J. & Jones, B.W. (2008). Jupiter – friend or foe? I: the asteroids. Int. J. Astrobiology 7(3–4), 251261.CrossRefGoogle Scholar
Laasko, T., Rantala, J. & Kaasalainen, M. (2006). Gravitational scattering by giant planets. Astron. Astrophys. 456, 373378.Google Scholar
Levison, H.F. & Duncan, M.J. (1997). From the Kuiper Belt to Jupiter-family comets: the spatial distribution of ecliptic comets. Icarus 127, 1332.CrossRefGoogle Scholar
Levison, H.F., Terrell, D., Wiegert, P.A., Dones, L. & Duncan, M.J. (2006). On the origin of the unusual orbit of comet 2P/Encke. Icarus 182, 161168.CrossRefGoogle Scholar
Matese, J.J. & Lissauer, J.J. (2004). Perihelion evolution of observed new comets implies the dominance of the galactic tide in making Oort cloud comets discernable. Icarus 170, 508513.CrossRefGoogle Scholar
Wetherill, G.W. (1994). Possible consequences of absence of Jupiters in planetary systems. Astrophys. Space Sci. 212, 2332.CrossRefGoogle ScholarPubMed