scholarly journals Conditions for the appearance of stars with a rotation opposite to the orbital rotation of their planets

2021 ◽  
pp. 22-25
Author(s):  
А.В. Тутуков ◽  
А.В. Федорова
Keyword(s):  
Molecular Clouds ◽  
Planetary System ◽  
Planetary Systems ◽  
Central Star ◽  
Giant Molecular Clouds ◽  
Relative Speed ◽  
Solar Mass ◽  
Orbital Rotation ◽  
Direction Opposite ◽  
Central Stars

Обнаружение планетной системы K2-290 A с двумя копланарными планетами, которые обращаются в направлении, обратном вращению центральной звезды, ставит задачу поиска адекватного сценария возникновения таких систем. В данной статье представленные нами ранее сценарии образования планетных систем пересматриваются для оценки возможности формирования в их рамках планет с орбитальным вращением, обратным вращению их центральных звезд. Оценки показывают, что аккреция холодного газа гигантских молекулярных облаков старыми звездами солнечной массы, движущимися в этих облаках с низкой относительной скоростью менее ∼ 1 км/с - это наиболее вероятный сценарий возникновения таких планетных систем. С другой стороны, обратное вращение только одной из нескольких планет системы может быть результатом взаимодействия близких массивных планет на неустойчивых орбитах. Detection of planetary system K2-290 A with two coplanar planets, which rotate in the direction opposite to the rotation of the central star, poses the problem of finding an adequate scenario for the emergence of such systems. In this article, the scenarios for the formation of planetary systems are revised to assess the possibility of forming within their framework planets with orbital rotation opposite to the rotation of their central stars. Estimates show that the accretion of cold gas from giant molecular clouds (GMOs) by old solar-mass stars moving in GMOs with a relative speed less than ∼ 1 km/s - this is the most probable scenario for the emergence of such planetary systems. On the other hand, the opposite rotation of only one of the several planets of the system can be the result of interaction of nearby massive planets in unstable orbits.

scholarly journals Fly-by encounters between two planetary systems I: Solar system analogues

2019 ◽  
Vol 488 (1) ◽  
pp. 1366-1376 ◽  
Author(s):  
Daohai Li ◽  
Alexander J Mustill ◽  
Melvyn B Davies
Keyword(s):  
Solar System ◽  
Planetary System ◽  
Planetary Systems ◽  
Open Clusters ◽  
Giant Planets ◽  
Direct Imaging ◽  
Solar Mass ◽  
Close Encounters ◽  
Large Numbers

ABSTRACTStars formed in clusters can encounter other stars at close distances. In typical open clusters in the Solar neighbourhood containing hundreds or thousands of member stars, 10–20 per cent of Solar-mass member stars are expected to encounter another star at distances closer than 100 au. These close encounters strongly perturb the planetary systems, directly causing ejection of planets or their capture by the intruding star, as well as exciting the orbits. Using extensive N-body simulations, we study such fly-by encounters between two Solar system analogues, each with four giant planets from Jupiter to Neptune. We quantify the rates of loss and capture immediately after the encounter, e.g. the Neptune analogue is lost in one in four encounters within 100 au, and captured by the flying-by star in 1 in 12 encounters. We then perform long-term (up to 1 Gyr) simulations investigating the ensuing post-encounter evolution. We show that large numbers of planets are removed from systems due to planet–planet interactions and that captured planets further enhance the system instability. While encounters can initially leave a planetary system containing more planets by inserting additional ones, the long-term instability causes a net reduction in planet number. A captured planet ends up on a retrograde orbit in half of the runs in which it survives for 1Gyr; also, a planet bound to its original host star but flipped during the encounter may survive. Thus, encounters between planetary systems are a channel to create counter-rotating planets, This would happen in around 1 per cent of systems, and such planets are potentially detectable through astrometry or direct imaging.

scholarly journals Planetary Systems and Stellar Multiplicity

1977 ◽  
Vol 33 ◽  
pp. 175-187
Author(s):  
Su-Shu Huang
Keyword(s):  
Planetary System ◽  
Genetic Difference ◽  
Surrounding Medium ◽  
Planetary Systems ◽  
Rotating Disk ◽  
Central Star ◽  
Dust Particles ◽  
Basic Point ◽  
Multiple Systems ◽  
Orbital Periods

AbstractIn this paper we have discussed the origin of planetary systems on one hand and binary and multiple stars on the other. First we show that phenomenological differences between these two kinds of celestial objects are due to their genetic difference. The basic point is that formation of a planetary system around a star has to be a minor event in the life history of the star while formation of a binary or multiple system has to be an event that is important equally to all components of the system. Thus the planetary system evolves from a rotating disk of gaseous and dust particles that comes into being after the star has already been there. It is therefore reasonable to suggest that the rotating disk results from transfer of angular momentum from the central star to the surrounding medium which is likely a residue left over in the process of formation of the central star.Binary and multiple systems cannot be formed in this way because they do not show the characteristics of having come out of a rotating disk. The dominant mechanism of their formation is that they were formed naturally as they are, each from perhaps a single condensation in the interstellar medium. However such a single mechanism of formation cannot satisfactorily explain the observed spread of binaries in mean separations between two components (or equivalently orbital periods). But the disagreement may be removed by including a small number of binaries formed by other processes and by considering the change of orbital elements of binaries after their formation. Trapezia were likely formed also by more than one mechanism.That several stars could be formed, from a single condensation requires the” existence oí pre-stellar nuclei which are briefly: discussed at the end of the paper.

scholarly journals Winds in hot, subluminous stars

1979 ◽  
Vol 83 ◽  
pp. 99-102 ◽  
Author(s):  
Sara R. Heap
Keyword(s):  
Mass Loss ◽  
High Velocity ◽  
Central Star ◽  
Stellar Winds ◽  
Solar Mass ◽  
Hot Stars ◽  
Ob Stars ◽  
International Ultraviolet Explorer ◽  
Different Types ◽  
Central Stars

Recent observations with the International Ultraviolet Explorer (IUE) satellite show that two very different types of hot stars have stellar winds: not only do the young, massive OB stars (the subjects of our discussion in this symposium, so far) undergo high-velocity mass-loss, but so also do hot evolved, solar mass stars, among them the central star of planetary nebulae. In this talk, I would like to show ultraviolet spectra of two central stars, the nuclei of NGC 6826 and Abell 78, and to describe how the characteristics of these spectra may be used to derive information concerning winds in these stars and in hot stars in general.

scholarly journals Episodes of Emission Lines in the Spectra of Red Giants as Signatures of Remnant Planetary Systems

2004 ◽  
Vol 202 ◽  
pp. 115-117
Author(s):  
G. M. Rudnitskij
Keyword(s):  
Solar System ◽  
Short Distance ◽  
Planetary System ◽  
Planetary Systems ◽  
Emission Lines ◽  
Circumstellar Envelope ◽  
Red Giants ◽  
Medium Effects ◽  
Solar Mass ◽  
Red Giant

When a star with a mass of about 1 solar mass enters the red giant stage of its evolution, the radius of its atmosphere reaches several astronomical units. If the star possessed during its mainsequence life a planetary system, similar to the solar system, the planets will be embedded into a rather dense and hot medium. Effects of a planet revolving around a red giant at a short distance (inside its circumstellar envelope) are discussed. Systematic monitoring of the spectra of red giants may reveal periodicities in the emergence of shock-induced emission lines and thus to detect probable remnant planetary systems around these stars.

scholarly journals TATOO: Tidal-chronology standalone tool to estimate the age of massive close-in planetary systems

2020 ◽  
Vol 641 ◽  
pp. A38
Author(s):  
F. Gallet
Keyword(s):  
Orbital Period ◽  
Planetary System ◽  
Interpolation Method ◽  
Planetary Systems ◽  
Central Star ◽  
Numerical Code ◽  
Mass Star ◽  
Stellar Rotation ◽  
Orbital Periods ◽  
The Impact

Context. The presence of a massive close-in planet with an orbital period of a few days or less around a low-mass star can possibly result in a strong variation in the properties of the central star. Indeed, star-planet tidal interactions generate exchanges of angular momentum that can result in tidal spin-up. This effect could then lead to gyrochronological ages biased towards younger ages. Aims. This article provides the community with TATOO, a standalone tool based on tidal-chronology, with which to estimate the age of a massive close-in planetary system using only its observed properties: mass of the planet and the star, stellar rotation, and planetary orbital periods. Methods. I used a star-planet tidal evolution numerical code to create a large multi-parametric grid of the evolution of synthetic star-planet systems. Furthermore, using the tidal-chronology technique, I employed a 3D interpolation method to provide a fairly precise age estimate of any given planetary system composed of one massive close-in planet. Results. About half of the planetary systems investigated in this work are subject to tidal spin-up bias. I pointed out that this bias linearly scales with the ratio between rotation and orbital period, making this quantity a useful proxy to rapidly investigate whether tidal-chronology needs to be used. Moreover, while being model dependent, TATOO can also be used even if no rotational departure is present. In that case, it gives results in agreement with the classical gyrochronological analysis. Conclusions. TATOO is a useful tool specifically designed for massive close-in planetary systems that can also be used as a classical gyrochronological tool. For now it is the only publicly available software to estimate the age of massive close-in planetary systems subject to tidal spin-up. In that sense, tidal-chronology can be seen as a first order correction of the impact of tidal interaction on gyrochronology.

scholarly journals Molecules in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 415-420 ◽  
Author(s):  
R. S. Booth ◽  
Th. De Graauw
Keyword(s):  
High Resolution ◽  
Molecular Clouds ◽  
Short Review ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Giant Molecular Clouds ◽  
Interstellar Molecules ◽  
First Time ◽  
Excitation Conditions

In this short review we describe recent new observations of millimetre transitions of molecules in selected regions of the Magellanic Clouds. The observations were made using the Swedish-ESO Submillimetre Telescope, SEST, (Booth et al. 1989), the relatively high resolution of which facilitates, for the first time, observations of individual giant molecular clouds in the Magellanic Clouds. We have mapped the distribution of the emission from the two lowest rotational transitions of 12CO and 13CO and hence have derived excitation conditions for the molecule. In addition, we have observed several well-known interstellar molecules in the same regions, thus doubling the number of known molecules in the Large Magellanic Cloud (LMC). The fact that all the observations have been made under controlled conditions with the same telescope enables a reasonable intercomparison of the molecular column densities. In particular, we are able to observe the relative abundances among the different isotopically substituted species of CO.

scholarly journals Planetary Nebula Evolution Traced by Distance-Independent Parameters

1993 ◽  
Vol 155 ◽  
pp. 480-480
Author(s):  
C.Y. Zhang ◽  
S. Kwok
Keyword(s):  
Physical Properties ◽  
Mass Distribution ◽  
Planetary Nebula ◽  
Strong Support ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolution Model ◽  
The Core ◽  
Independent Parameters ◽  
Central Stars

Making use of the results from recent infrared and radio surveys of planetary nebulae, we have selected 431 nebulae to form a sample where a number of distance-independent parameters (e.g., Tb, Td, I60μm and IRE) can be constructed. In addition, we also made use of other distance-independent parameters ne and T∗ where recent measurements are available. We have investigated the relationships among these parameters in the context of a coupled evolution model of the nebula and the central star. We find that most of the observed data in fact lie within the area covered by the model tracks, therefore lending strong support to the correctness of the model. Most interestingly, we find that the evolutionary tracks for nebulae with central stars of different core masses can be separated in a Tb-T∗ plane. This implies that the core masses and ages of the central stars can be determined completely independent of distance assumptions. The core masses and ages have been obtained for 302 central stars with previously determined central-star temperatures. We find that the mass distribution of the central stars strongly peaks at 0.6 M⊙, with 66% of the sample having masses <0.64 MM⊙. The luminosities of the central stars are then derived from their positions in the HR diagram according to their core masses and central star temperatures. If this method of mass (and luminosity) determination turns out to be accurate, we can bypass the extremely unreliable estimates for distances, and will be able to derive other physical properties of planetary nebulae.

scholarly journals Effects of initial density profiles on massive star cluster formation in giant molecular clouds

2021 ◽  
Author(s):  
Yingtian Chen ◽  
Hui Li ◽  
Mark Vogelsberger
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Initial Density ◽  
Giant Molecular Clouds ◽  
Density Profiles ◽  
Stellar Feedback ◽  
Gas Accretion

Abstract We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ‘hierarchically’ to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ‘accretion’ mode from centrally-concentrated clouds in the early Universe.

scholarly journals DESTINY: Database for the Effects of STellar encounters on dIsks and plaNetary sYstems

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Asmita Bhandare ◽  
Susanne Pfalzner
Keyword(s):  
Planetary System ◽  
Planetary Systems ◽  
Gravitational Effect ◽  
Parameter Study ◽  
Orbital Inclination ◽  
Particle Properties ◽  
Disk Size ◽  
Stellar Group ◽  
Cluster Environment ◽  
Parabolic Orbits

Abstract Most stars form as part of a stellar group. These young stars are mostly surrounded by a disk from which potentially a planetary system might form. Both, the disk and later on the planetary system, may be affected by the cluster environment due to close fly-bys. The here presented database can be used to determine the gravitational effect of such fly-bys on non-viscous disks and planetary systems. The database contains data for fly-by scenarios spanning mass ratios between the perturber and host star from 0.3 to 50.0, periastron distances from 30 au to 1000 au, orbital inclination from 0∘ to 180∘ and angle of periastron of 0∘, 45∘ and 90∘. Thus covering a wide parameter space relevant for fly-bys in stellar clusters. The data can either be downloaded to perform one’s own diagnostics like for e.g. determining disk size, disk mass, etc. after specific encounters, obtain parameter dependencies or the different particle properties can be visualized interactively. Currently the database is restricted to fly-bys on parabolic orbits, but it will be extended to hyperbolic orbits in the future. All of the data from this extensive parameter study is now publicly available as DESTINY.

scholarly journals The Ballistic Particle Model

1983 ◽  
Vol 100 ◽  
pp. 133-134
Author(s):  
Frank N. Bash
Keyword(s):  
Radial Velocity ◽  
Gravitational Potential ◽  
Molecular Clouds ◽  
Milky Way ◽  
Terminal Velocity ◽  
Particle Model ◽  
The Sun ◽  
Giant Molecular Clouds ◽  
Spiral Pattern ◽  
Armed Spiral

Bash and Peters (1976) suggested that giant molecular clouds (GMC's) can be viewed as ballistic particles launched from the two-armed spiral-shock (TASS) wave with orbits influenced only by the overall galactic gravitational potential perturbed by the spiral gravitational potential in the arms. For GMC's in the Milky Way, the model predicts that the radial velocity observed from the Sun increases with age (time since launch). We showed that the terminal velocity of CO observed from l ≃ 30° to l ≃ 60° can be understood if all GMC's are born in the spiral pattern given by Yuan (1969) and live 30 × 106 yrs. Older GMC's were predicted to have radial velocities which exceed observed terminal velocities.

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