Statistical properties of exoplanets IV. The period--eccentricity relations of exoplanets and of binary stars

A sample of spectroscopic binaries and a sample of single planetary systems, both having main-sequence solar-type primary components, are selected in order to compare their eccentricities. The positions of the objects in the (P.(1-e^2)^(3/2), e) plane is used to determine parts in the period-eccentricity diagram that are not affected by tidal circularization. The original eccentricities of binaries and planets are derived and compared. They seem to be weakly or not at all correlated with period in both samples, but two major differences are found :(1) The tidal circularization of planetary orbits is almost complete for periods shorter than 5 days, but it is not visible when P.(1-e^2)^{3/2} is longer than this limit. This suggests that the circularization occurs rapidly after the end of the migration process and is probably simultaneous with the end of the formation of the planet. By contrast, we confirm that the circularization of the binary orbits is a process still progressing a long time after the formation of the systems.(2) Beyond the circularization limit, the eccentricities of the orbits of the planets are significantly smaller than those of binary orbits, and this discrepancy cannot be due to a selection effect. Moreover, the eccentricities of binaries with small mass ratios are quite similar to those of all binaries with q<0.8. This suggests that the low eccentricities of exoplanet orbits are not a consequence of low-mass secondaries in a universal process. These remarks are in favor of the idea that binaries and exoplanets are two different classes of object from the point of view of their formation.Comment: To be published in Astronomy & Astrophysics (in press) 10 pages, 7 figure

How special is the Solar System?

Most mechanisms proposed for the formation of planets are modified versions of the mechanism proposed for the solar system. Here we argue that, in terms of those planetary systems which have been observed, the case for the solar system being a typical planetary system has yet to be established. We consider the possibility that most observed planetary systems have been formed in some quite different way. If so, it may be that none of the observed planetary systems is likely to harbour an earth-like planet.Comment: 6 pages, 3 figures, MNRAS accepte

Are elite cricketers more prone to suicide? A psychological autopsy study of Test cricketer suicides

Objectives: It has been hypothesised that the very nature of the game predisposes elite cricketers to higher rates of suicide. Aim: We aim to estimate the suicide rate of male Test cricketers and to determine the reasons for suicide. Methods: The suicide rate in male Test cricketers was determined. A psychological autopsy was conducted using published biographical data. Results: Twenty suicides amongst 2794 male Test cricketers from 1877 to 2014 yielded a suicide rate of 715.4 per 100,000 for that period. Health, financial and relationship issues were prominent; depression and alcohol misuse were common. Conclusions: Most suicides in Test cricketers occurred post-retirement in mid to late life with similar correlates to those found in the general male population. The idiosyncrasies of cricket are unlikely to contribute to suicide; however, the post-retirement welfare of Test cricketers should remain a focus of concern and the greater supports available to contemporary Test cricketers needs to extend beyond retirement