Galactic disc dark matter, terrestrial impact cratering and the law of large numbers

Stothers, Richard B.

doi:10.1046/j.1365-8711.1998.02001.x

Cited by 64 publications

(45 citation statements)

References 53 publications

(74 reference statements)

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“…If we further adopt a crossing frequency of ∼ 30 Myr it appears plausible -and there is a long debate in the literature that reaches back to the 1970s (e.g. Grieve & Pesonen 1996, Stothers 1998, Jetsu & Pelt 2000, and many references therein) -that the Sun's orbital motion might have triggered the paleontological record of mass extinctions and of the major impact events, the most recent of which are: the Popigai (Diam. ø ∼ 100 km) and Chesapeake Bay (ø ∼ 90 km) impact structures both at ∆τ ∼ 35 Myr, and the Chicxulub (ø ∼ 180-300 km) and Morokweng (ø ∼ 340 km) at ∆τ ∼ 65 Myr and ∆τ ∼ 145 Myr, respectively (see Table 1 in Montanari, Campo Bagatin, & Farinella 1998, and references therein).…”

Section: Discussionmentioning

confidence: 99%

Nearby stars of the Galactic disk and halo. III.

2003

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Abstract. High-resolution spectroscopic observations of about 150 nearby stars or star systems are presented and discussed. The study of these and another 100 objects of the previous papers of this series implies that the Galaxy became reality 13 or 14 Gyr ago with the implementation of a massive, rotationally-supported population of thick-disk stars. The very high star formation rate in that phase gave rise to a rapid metal enrichment and an expulsion of gas in supernovae-driven Galactic winds, but was followed by a star formation gap for no less than three billion years at the Sun's galactocentric distance. In a second phase, then, the thin disk -our "familiar Milky Way" -came on stage. Nowadays it traces the bright side of the Galaxy, but it is also embedded in a huge coffin of dead thick-disk stars that account for a large amount of baryonic dark matter. As opposed to this, cold-dark-matter-dominated cosmologies that suggest a more gradual hierarchical buildup through mergers of minor structures, though popular, are a poor description for the Milky Way Galaxy -and by inference many other spirals as well -if, as the sample implies, the fossil records of its long-lived stars do not stick to this paradigm. Apart from this general picture that emerges with reference to the entire sample stars, a good deal of the present work is however also concerned with detailed discussions of many individual objects. Among the most interesting we mention the blue straggler or merger candidates HD 165401 and HD 137763/HD 137778, the likely accretion of a giant planet or brown dwarf on 59 Vir in its recent history, and HD 63433 that proves to be a young solar analog at τ ∼ 200 Myr. Likewise, the secondary to HR 4867, formerly suspected non-single from the Hipparcos astrometry, is directly detectable in the highresolution spectroscopic tracings, whereas the visual binary χ Cet is instead at least triple, and presumably even quadruple. With respect to the nearby young stars a complete account of the Ursa Major Association is presented, and we provide as well plain evidence for another, the "Hercules-Lyra Association", the likely existence of which was only realized in recent years. On account of its rotation, chemistry, and age we do confirm that the Sun is very typical among its G-type neighbors; as to its kinematics, it appears however not unlikely that the Sun's known low peculiar space velocity could indeed be the cause for the weak paleontological record of mass extinctions and major impact events on our parent planet during the most recent Galactic plane passage of the solar system. Although the significance of this correlation certainly remains a matter of debate for years to come, we point in this context to the principal importance of the thick disk for a complete census with respect to the local surface and volume densities. Other important effects that can be ascribed to this dark stellar population comprise (i) the observed plateau in the shape of the luminosity function of the local FGK stars, (ii) a small though syst...

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Section: Discussionmentioning

confidence: 99%

Nearby stars of the Galactic disk and halo. III.

2003

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“…The periodicity in these catastrophes is disputed, however (see for instance Jetsu & Pelt 2000). The spectral analysis of the periodicity hypothesis in cratering records shows, in the most recently published works, possible or significant periods: 33 ± 4 Myr (Rampino & Stothers 1984), 33 ± 1 Myr (Stothers 1998), and more recently 16.1 Myr and 34.7 Myr by Moon et al (2003). We note that some authors estimate that periodicities could result from a spurious "human-signal" such as rounding (Jetsu & Pelt 2000).…”

Section: Terrestrial Impact Crateringmentioning

confidence: 92%

Vertical distribution of Galactic disk stars

Bienaymé¹,

Soubiran

Mishenina

et al. 2006

A&A

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We used red clump stars to measure the surface mass density of the Galactic disk in the solar neighbourhood. High resolution spectra of red clump stars towards the NGP have been obtained with the ELODIE spectrograph at OHP for Tycho-2 selected stars, and nearby Hipparcos counterparts were also observed. We determined their distances, velocities, and metallicities to measure the gravitational force law perpendicular to the Galactic plane. As in most previous studies, we applied one-parameter models of the vertical gravitational potential. We obtained a disk surface mass density within 1.1 kpc of the Galactic plane, Σ 1.1 kpc = 64 ± 5 M pc −2 , with an excellent formal accuracy, however we found that such one-parameter models can underestimate the real uncertainties. Applying two-parameter models, we derived more realistic estimates of the total surface mass density within 800 pc from the Galactic plane, Σ 0.8 kpc = 57-66 M pc −2 , and within 1.1 kpc, Σ 1.1 kpc = 57-79 M pc −2 . This can be compared to literature estimates of ∼40 M pc −2 in stars and to 13 M pc −2 in the less accurately measured ISM contribution. We conclude that there is no evidence of large amounts of dark matter in the disk and, furthermore, that the dark matter halo is round or not vey much flattened. A by-product of this study is the determination of the half period of oscillation by the Sun through the Galactic plane, 42 ± 2 Myr, which cannot be related to the possible period of large terrestrial impact craters ∼33-37 Myr.

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“…For a quarter of a century, evidence that confirms the existence of real periodicity in these catastrophic events has been published, e.g. by Stothers (1998), Moon et al (2003), Yabushita (2004), Chang & Moon (2005), Stothers (2006) and Wickramasinghe & Napier (2008). Evidence against such periodicity has also been presented, e.g.…”

Section: Introductionmentioning

confidence: 93%

Detection of real periodicity in the terrestrial impact crater record: quantity and quality requirements

Lyytinen

Jetsu

Kajatkari

et al. 2009

A&A

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Aims. To determine the quantity and quality requirements for the terrestrial impact crater data which would allow reliable detection of real periodicity. Methods. Artificial impact crater data samples of different size and accuracy are simulated. Erosion is considered, as well as the effect of the unknown ratio between periodic and aperiodic impacts. The probabilities for detecting real and false periodicities are solved with the Rayleigh test from these simulated data.Results. Reliable detection of real periodicity is currently impossible -unless all impacts on Earth have been periodic.

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Galactic disc dark matter, terrestrial impact cratering and the law of large numbers

Cited by 64 publications

References 53 publications

Nearby stars of the Galactic disk and halo. III.

Nearby stars of the Galactic disk and halo. III.

Vertical distribution of Galactic disk stars

Detection of real periodicity in the terrestrial impact crater record: quantity and quality requirements

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