1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.

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The Exoplanet Handbook

Cycles in Fossil Diversity Robert A. Rohde & Richard A. Muller Department of Physics and Lawrence Berkeley Laboratory University of California, Berkeley California 94720 USA Report LBNL-56544 20 October 2004 submitted to Nature It is well-known that the diversity of life appears to fluctuate during the course the Phanerozoic, the eon during which hard shells and skeletons left abundant fossils (0-542 Ma). Using Sepkoski's compendium 1 of the first and last stratigraphic appearances of 36380 marine genera, we report a strong 62 ± 3 Myr cycle, which is particularly strong in the shorter-lived genera. The five great extinctions enumerated by Raup and Sepkoski 2 may be an aspect of this cycle. Because of the high stastical significance, we also consider contributing environmental factors and possible causes. Sepkoski's posthumously published Compendium of Fossil Marine Animal Genera , and its earlier versions, has frequently been used in the study of biodiversity and extinction 3-4 . For our purposes, diversity is defined as the number of distinct genera alive at any given time, i.e. those whose first occurrence predates and last occurrence postdates that time. Because Sepkoski references only 295 stratigraphic intervals, the International Commission on Stratigraphy's 2004 time scale 5 is used to translate the stratigraphic records into a record of diversity vs. time, with details given in the supplement. Though Sepkoski's is the most extensive compilation available, it is known to be subject to certain systematic limitations due primarily to the varying availability and quality of geologic sections 6-7 , the implications of this will be discussed where appropriate. Fig. 1A shows diversity vs. time for all 36380 genera in Sepkoski’s compendium. In Fig. 1B we show the 17797 genera that remain when we remove those with uncertain ages (given only at epoch or period level), and those with only a single occurrence. The smooth trend curve through the data is the third-order polynomial that minimizes the variance of the difference between it and the data. The overall shape of 1A and 1B is similar to those previously published for fossil families 2 and for genera 3 . It rises rapidly at the beginning of the Phanerozoic (right side), drops to a nadir near the Permian- Triassic boundary (251 Ma), and then rises steeply until the present. These variations may result from evolutionary and environmental drivers 8 , observational biases 6 , or changes in the number of available geologic sections 7 ; for example, the sharp rise towards the present may be driven by the greater availability and study of recent sections. Our focus is not on the trend but on the short-term variations shown in 1C, obtained by subtracting the trend from 1B. The Fourier spectrum of 1C is shown in 1E. It is dominated by a strong peak with period 62 ± 3 Myr (frequency 0.016 cycles/Myr). The sine wave corresponding to this cycle is also shown in Fig. 1C, where it accounts for 35% of the variance. Note that because steep drops in diversity are often followed by gradual recoveries, the peaks and valleys in the data don’t precisely align with those of the sine curve. Also, some abrupt features may appear more gradual because of incomplete records. 9 We indicate the 5 major extinction events of Raup and Sepkoski 2

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Cycles in fossil diversity

PLANETARY SYSTEMS, the solar system amongst them, are believed to form as inevitable and common byproducts of star formation For orientation, an overview of the processes described in this chapter is as follows The present paradigm starts with star formation in molecular clouds Brown dwarfs are formed as the lowmass tail of this process, although some may be formed as a high-mass tail of planet formation Gas and dust in the collapsing molecular cloud which does not fall directly onto the protostar resides in a relatively long-lived accretion disk which provides the environment for the subsequent stages of planet formation Terrestrial-mass planets are formed within the disk through the progressive agglomeration of material denoted, as it grows in size, as dust, rocks, planetesimals and protoplanets A similar process typically occurring further out in the disk results in the cores of giant planets, which then gravitationally accumulate their mantles of ice and/or gas As the planet-forming bodies grow in mass, growth and dynamics become more dominated by gravitational interactions Towards the final phases, and before the remaining gas is lost through accretion or dispersal, the gas provides a viscous medium at least partially responsible for planetary migration Some migration also occurs during these later stages as a result of gravitational scattering between the (proto-)planets and the residual sea of planetesimals The final structural stabilisation of the planetary system may be affected by planet–planet interactions, until a configuration emerges which may be dynamically stable over billions of years The current observational data for exoplanet systems is broadly compatible with this overall picture Other constraints come from a substantial body of detailed observations of the solar system (Chapter 12) Context and present paradigm An understanding of howplanets formis essential in understanding and interpreting the considerable range of observed planetary system architectures and dynamics Today, the most widely considered solar nebula theory holds that planet formation in the solar system, and by inference in other exoplanet systems, follows on from the process of star formation and accretion disk formation, through the agglomeration of residual material as the protoplanetary disk collapses and evolves

The Exoplanet Handbook: Formation and evolution

A review of space tether research

We modeled the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.

The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way

The statistical Drake equation

The KLT (Karhunen–Loève Transform) to extend SETI searches to broad-band and extremely feeble signals

Darwinian evolution theory may be regarded as a part of SETI theory in that the factor fl in the Drake equation represents the fraction of planets suitable for life on which life actually arose. In this paper we firstly provide a statistical generalization of the Drake equation where the factor fl is shown to follow the lognormal probability distribution. This lognormal distribution is a consequence of the Central Limit Theorem (CLT) of Statistics, stating that the product of a number of independent random variables whose probability densities are unknown and independent of each other approached the lognormal distribution when the number of factors increased to infinity. In addition we show that the exponential growth of the number of species typical of Darwinian Evolution may be regarded as the geometric locus of the peaks of a one-parameter family of lognormal distributions (b-lognormals) constrained between the time axis and the exponential growth curve. Finally, since each b-lognormal distribution in the family may in turn be regarded as the product of a large number (actually “an infinity”) of independent lognormal probability distributions, the mathematical way is paved to further cast Darwinian Evolution into a mathematical theory in agreement with both its typical exponential growth in the number of living species and the Statistical Drake Equation.

Claudio Maccone

Papers

The statistical Drake equation

The KLT (Karhunen–Loève Transform) to extend SETI searches to broad-band and extremely feeble signals

A Mathematical Model for Evolution and SETI

Advantages of Karhunen–Loève transform over fast Fourier transform for planetary radar and space debris detection

ASTROSAIL and SETISAIL: Two extrasolar system missions to the Sun's gravitational focuses