orbital motion
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2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Jorge A. Pérez-Hernández ◽  
Luis Benet

AbstractThe leading source of uncertainty to predict the orbital motion of asteroid (99942) Apophis is a non-gravitational acceleration arising from the anisotropic thermal re-emission of absorbed radiation, known as the Yarkovsky effect. Previous attempts to obtain this parameter from astrometry for this object have only yielded marginally small values, without ruling out a pure gravitational interaction. Here we present an independent estimation of the Yarkovsky effect based on optical and radar astrometry which includes observations obtained during 2021. Our numerical approach exploits automatic differentiation techniques. We find a non-zero Yarkovsky parameter, A2 = (−2.899 ± 0.025) × 10−14 au d−2, with induced semi-major axis drift of (−199.0 ± 1.5) m yr−1 for Apophis. Our results provide definite collision probability predictions for the close approaches in 2029, 2036, and 2068.


2022 ◽  
Vol 163 (2) ◽  
pp. 52
Author(s):  
Aldo G. Sepulveda ◽  
Brendan P. Bowler

Abstract HR 8799 is a young A5/F0 star hosting four directly imaged giant planets at wide separations (∼16–78 au), which are undergoing orbital motion and have been continuously monitored with adaptive optics imaging since their discovery over a decade ago. We present a dynamical mass of HR 8799 using 130 epochs of relative astrometry of its planets, which include both published measurements and new medium-band 3.1 μm observations that we acquired with NIRC2 at Keck Observatory. For the purpose of measuring the host-star mass, each orbiting planet is treated as a massless particle and is fit with a Keplerian orbit using Markov chain Monte Carlo. We then use a Bayesian framework to combine each independent total mass measurement into a cumulative dynamical mass using all four planets. The dynamical mass of HR 8799 is 1.47 − 0.17 + 0.12 M ⊙ assuming a uniform stellar mass prior, or 1.46 − 0.15 + 0.11 M ⊙ with a weakly informative prior based on spectroscopy. There is a strong covariance between the planets’ eccentricities and the total system mass; when the constraint is limited to low-eccentricity solutions of e < 0.1, which are motivated by dynamical stability, our mass measurement improves to 1.43 − 0.07 + 0.06 M ⊙. Our dynamical mass and other fundamental measured parameters of HR 8799 together with Modules for Experiments in Stellar Astrophysics Isochrones and Stellar Tracks grids yields a bulk metallicity most consistent with [Fe/H] ∼ −0.25–0.00 dex and an age of 10–23 Myr for the system. This implies hot-start masses of 2.7–4.9 M Jup for HR 8799 b and 4.1–7.0 M Jup for HR 8799 c, d, and e, assuming they formed at the same time as the host star.


2021 ◽  
Author(s):  
manfred geilhaupt

Abstract In Quantum Physics, the Spin of an elementary particle is defined to be an intrinsic,inherent property. The same to the magnetic moment (μ) due to the spin of chargedparticles - like Electron (me) and Proton (mp). So the intrinsic spin (S=1/2h-bar) of theelectron entails a magnetic moment because of charge (e). However, a magnetic momentof a charged particle can also be generated by a circular motion (due to spin) of anelectric charge (e), forming a current. Hence the orbital motion (of charge around a massnucleus)generates a magnetic moment by Ampère’s law. This concept must lead to analternative way calculating the neutrino mass (mν) while looking at the beta decay of aneutron into fragments: proton, electron, neutrino and corresponding kinetic energies. Thechange of neutrons magnetic moment (μn) during the decay process is a fact based onenergy and spin and charge conservation, so should allow to calculate the restmass ofthe charge-less neutrino due to a significant change of: μe= -9.2847647043(28)E-24J/Tdown to μev= -9.2847592533(28)E-24J/T (while assuming mv=0.30eV to be absorbed and if(g-2)/2 from QED remains constant). As always the last word has the experiment.


Author(s):  
Hicham Ferroudji ◽  
Ahmed Hadjadj ◽  
Titus Ntow Ofei ◽  
Rahul Narayanrao Gajbhiye ◽  
Mohammad Azizur Rahman ◽  
...  

AbstractTo ensure an effective drilling operation of an explored well, the associated hydraulics program should be established carefully based on the correct prediction of a drilling fluid’s pressure drop and velocity field. For that, the impact of the drill string orbital motion should be considered by drilling engineers since it has an important influence on the flow of drilling fluid and cuttings transport process. In the present investigation, the finite volume method coupled with the sliding mesh approach is used to analyze the influence of the inner cylinder orbital motion on the flow of a power-law fluid (Ostwald-de Waele) in an annular geometry. The findings indicate that the orbital motion positively affects the homogeneity of the power-law axial velocity through the entire eccentric annulus; however, this impact diminishes as the diameter ratio increases. In addition, higher torque is induced when the orbital motion occurs, especially for high values of eccentricity and diameter ratio; nonetheless, a slight decrease in torque is recorded when the fluid velocity increases.


2021 ◽  
Vol 923 (1) ◽  
pp. 13
Author(s):  
Sergey A. Cherkis ◽  
Maxim Lyutikov

Abstract We consider topological configurations of the magnetically coupled spinning stellar binaries (e.g., merging neutron stars or interacting star–planet systems). We discuss conditions when the stellar spins and the orbital motion nearly “compensate” each other, leading to very slow overall winding of the coupled magnetic fields; slowly winding configurations allow gradual accumulation of magnetic energy, which is eventually released in a flare when the instability threshold is reached. We find that this slow winding can be global and/or local. We describe the topology of the relevant space F = T 1 S 2 as the unit tangent bundle of the two-sphere and find conditions for slowly winding configurations in terms of magnetic moments, spins, and orbital momentum. These conditions become ambiguous near the topological bifurcation points; in certain cases, they also depend on the relative phases of the spin and orbital motions. In the case of merging magnetized neutron stars, if one of the stars is a millisecond pulsar, spinning at ∼10 ms, the global resonance ω 1 + ω 2 = 2Ω (spin-plus beat is two times the orbital period) occurs approximately one second before the merger; the total energy of the flare can be as large as 10% of the total magnetic energy, producing bursts of luminosity ∼1044 erg s−1. Higher order local resonances may have similar powers, since the amount of involved magnetic flux tubes may be comparable to the total connected flux.


2021 ◽  
pp. 217-234
Author(s):  
Richard Fitzpatrick
Keyword(s):  

2021 ◽  
Vol 13 (22) ◽  
pp. 4722
Author(s):  
Meng Sun ◽  
Yongzeng Yang ◽  
Yutao Chi ◽  
Tianqi Sun ◽  
Yongfang Shi ◽  
...  

Wave–current interaction in coastal regions is significant and complicated. Most wave models consider the influence of ocean current and water depth on waves, while the influence of the gradient of the sea bottom slope is not taken into account in most research. This study aimed to analyze and quantify the contribution of storm tidal currents to coastal ocean waves in a case where sea bottom slope was not ignored. Fourier analysis was applied to solve the governing equation and boundary conditions, and an analytic model for the calculation of the variation of amplitude of wave orbital motion was proposed. Ocean currents affect ocean waves through resonance. In this paper, an implemented instance of this analytic model was given, using the Shengsi area during Typhoon Malakas as an example. The results suggest that vertical variation in the amplitude of wave orbital motion is remarkable. The impact of wave–current interaction is noticeable where the gradient of the sea bottom slope is relatively large.


2021 ◽  
Author(s):  
manfred geilhaupt

Abstract In Quantum Physics the Spin of an elementary particle is defined to be an „intrinsic, inherent“ property. The same to the magnetic moment (μ) due to the spin of charged particles - like Electron (me) and Proton (mp). So the intrinsic spin (S=1/2h-bar) of the electron entails a magnetic moment because of charge (e). However, a magnetic moment of a charged particle can also be generated by a circular motion (due to spin) of an electric charge (e), forming a current. Hence the „orbital motion of charge“ around a „mass-nucleus“ generates a magnetic moment by Ampère’s law. This concept leads to an alternative way calculating the neutrino mass (mν) while discussing the beta decay of a neutron into fragments: proton, electron, neutrino and binding energy. The change of neutrons magnetic moment (μn) during the decay process based on energy and spin and charge conservation should allow to calculate the restmass of the neutrino. 
(KATRIN <1.1eV (2019) about 0.2eV (2021). Estimation from μn: 0.10(20)eV (2020).


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