Binary Star Hypothesis

Astrobiology, 2010

Alibert, Y.; Broeg, C.; Benz, W.; Wuchterl, G.; Grasset, O.; Sotin, C.

Astrophysics and Space Science, 1988

We develop a new thermodynamic approach to the problem of the last stages of star formation, when a collapsing fragment evolves adiabatically into its final state: single protostar, surrounded or not by protoplanetary disc, or binary system. In this context, we point out the crucial role of the angular momentum transfer: a very efficient mechanism tends to form double stars with small mass secondaries, while a total decoupling yields twin binaries. Intermediate assumptions allow the birth of both kinds of binary systems, as well as the formation of not very massive protoplanetary discs. Discs of larger mass, which would be required to produce protoplanetary systems as a consequence of dynamical instabilities, do not form under any circumstances. A representation of the outcomes as functions of the corresponding initial conditions on the usual c~ -flplane gives well definite regions for single stars, protoplanetary discs, unbalanced systems and twin binaries. On this ground, a preliminary estimate of the percentage of stars surrounded by planetary systems is possible. A particular numerical simulation confirms the bimodality of the mass ratio distribution as well as the main features of the e -fl plane partition. A few suggestions about non-adiabatic effects are also given. Our thermodynamic approach, supported by the numerical one and by the analysis of the observational statistics, allow to define a first unitary sketch for the formation of binary systems and protoplanetary discs.

Arxiv preprint arXiv: …, 2010

We review the current theoretical understanding how growth from micrometer sized dust to massive giant planets occurs in disks around young stars. After introducing a number of observational constraints from the solar system, from observed protoplanetary disks, and from the extrasolar planets, we simplify the problem by dividing it into a number of discrete stages which are assumed to occur in a sequential way. In the first stage -the growth from dust to kilometer sized planetesimals -the aerodynamics of the bodies are of central importance. We discuss both a purely coagulative growth mode, as well as a gravoturbulent mode involving a gravitational instability of the dust. In the next stage, planetesimals grow to protoplanets of roughly 1000 km in size. Gravity is now the dominant force. The mass accretion can be strongly non-linear, leading to the detachment of a few big bodies from the remaining planetesimals. In the outer planetary system (outside a few AU), some of these bodies can become so massive that they eventually accrete a large gaseous envelope. This is the stage of giant planet formation, as understood within the core accretiongas capture paradigm. We also discuss the direct gravitational collapse model where giant planets are thought to form directly via a gravitational fragmentation of the gas disk. In the inner system, protoplanets collide in the last stage -probably after the dispersal of the gaseous disk -in giant impacts until the separations between the remaining terrestrial planets become large enough to allow long term stability. We finish the review with some selected questions.

2007

The processes leading to star formation are one of main topics of research in astronomy. The area has developed rapidly during last decade, stimulated by the construction of large telescopes and the launch of space telescopes. There are still many unanswered questions concerning the early stages of star formation as well as the many detailed processes in the later stages.

Proceedings of Accretion Processes in Cosmic Sources – II — PoS(APCS2018), 2019

Discoveries of planets in binary star systems showed that planetary companions are not restricted to single stars and led to a growing interest in understanding planetary formation processes in general. In binary star systems, the proto-planetary disk is truncated due to the secondary star which has strong influence on the formation of planets. Despite numerous scientific studies thereto, we are still faced with many open questions regarding where and how a planet can grow in such environments as there are many parameters that affect the outcome of hydrodynamical simulations. In contrast thereto, terrestrial planet formation using gravitational N-body simulations can be easily performed. In either case, the architecture of a binary star-giant planet system influences the formation and evolution of additional planets. Furthermore, resonances play an important role for accretion processes and for the final set up of a planetary system.

EPJ Web of Conferences, 2011

The planetary mass-radius diagram is an observational result of central importance to understand planet formation. We present an updated version of our planet formation model based on the core accretion paradigm which allows us to calculate planetary radii and luminosities during the entire formation and evolution of the planets. We first study with it the formation of Jupiter, and compare with previous works. Then we conduct planetary population synthesis calculations to obtain a synthetic mass-radius diagram which we compare with the observed one. Except for bloated Hot Jupiters which can be explained only with additional mechanisms related to their proximity to the star, we find a good agreement of the general shape of the observed and the synthetic M − R diagram. This shape can be understood with basic concepts of the core accretion model.

Planetary and Space Science, 1982

Observational constraints on interior models of the giant planets indicate that these planets were all much hotter when they formed and they all have rock and/or ice cores of ten to thirty earth masses. These cores are probably soluble in the envelopes above, especially in Jupiter and Saturn, and are therefore likely to be primordial. They persist despite the continual upward mixing by thermally driven convection throughout the age of the solar system, because of the inefficiency of double-diffusive convection. Thus, these planets most probably formed by the hydrodynamic collapse of a gaseous envelope onto a core rather than by direct instability of the gaseous solar nebula. Recent calculations by Mizuno (1980, Prog. Theor. Phys. 64, 544) show that this formation mechanism may explain the similarity of giant planet core masses. Problems remain however, and no current model is entirely satisfactory in explaining the properties of the giant planets and simultaneously satisfying the terrestrial planet constraints. Satellite systematics and protoplanetary disk nebulae are also discussed and related to formation conditions.

viXra, 2017

It is a widely accepted misconception that the solar system would have been created by the collapse of nebulae around the solar region, just as our galaxy itself. Where this is true for the stars in the galaxy, this is definitely wrong for our planetary system. Indeed, many stars in our galaxy were created during the formation of our disk galaxy out of a regular, spherical or elliptical galaxy, due to the angular momentum of the galaxy's center, which contains fast spinning stars and black holes. This process has been extendedly explained in my book “Gravitomagnetism - including an introduction to the Coriolis Gravity Theory”. The disk was compressed by the angular gravity of the galaxy's center, a second gravity field on top of Newtonian Gravity. The smaller and colder parts were able to clump together and heathen up by that compression. Elsewhere, voids were created that way, and a heterogeneous disk, as our spiral disk galaxy shows us, could form. The difference between t...

Lecture Notes in Physics, 2010

The study of planet formation has been revolutionized by recent observational breakthroughs, which have allowed the detection and characterization of extrasolar planets, the imaging of protoplanetary disks, and the discovery of the Solar System's Kuiper Belt.