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Open AccessArticle

Alpha Centauri: Disc Dynamics, Planet Stability, Detectability

by Nicolás Cuello and Mario Sucerquia

Universe 2024, 10(2), 64; https://doi.org/10.3390/universe10020064 - 31 Jan 2024

Cited by 6 | Viewed by 3787 | Correction

Alpha Centauri is a triple stellar system, and it contains the closest star to Earth (Proxima Centauri). Over the last decades, the stars in Alpha Cen and their orbits have been investigated in great detail. However, the possible scenarios for planet formation and evolution in this triple stellar system remain to be explored further. First, we present a 3D hydrodynamical simulation of the circumstellar discs in the binary Alpha Cen AB. Then, we compute stability maps for the planets within Alpha Cen obtained through N-body integrations. Last, we estimate the radial velocity (RV) signals of such planets. We find that the circumstellar discs within the binary cannot exceed 3 au in radius and that the available dust mass to form planets is about 30

M_{\oplus}

. Planets around A and B are stable if their semimajor axes are below 3 au, while those around C are stable and remain unperturbed by the binary AB. For rocky planets, the planetary mass has only a mild effect on the stability. Therefore, Alpha Cen could have formed and hosted rocky planets around each star, which may be detected with RV methods in the future. The exoplanetary hunt in this triple stellar system must continue. Full article

(This article belongs to the Special Issue The Royal Road: Eclipsing Binaries and Transiting Exoplanets)

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8 pages, 626 KB

Open AccessProceeding Paper

Improving Inferences about Exoplanet Habitability

by Risinie D. Perera and Kevin H. Knuth

Phys. Sci. Forum 2023, 9(1), 7; https://doi.org/10.3390/psf2023009007 - 27 Nov 2023

Cited by 1 | Viewed by 1741

Abstract

Assessing the habitability of exoplanets (planets orbiting other stars) is of great importance in deciding which planets warrant further careful study. Planets in the habitable zones of stars like our Sun are sufficiently far away from the star so that the light rays from the star can be assumed to be parallel, leading to straightforward analytic models for stellar illumination of the planet’s surface. However, for planets in the close-in habitable zones of dim red dwarf stars, such as the potentially habitable planet orbiting our nearest stellar neighbor, Proxima Centauri, the analytic illumination models based on the parallel ray approximation do not hold, resulting in severe biases in the estimates of the planetary characteristics, thus impacting efforts to understand the planet’s atmosphere and climate. In this paper, we present our efforts to improve the instellation (stellar illumination) models for close-in orbiting planets and the significance of the implementation of these improved models into EXONEST, which is a Bayesian machine learning application for exoplanet characterization. The ultimate goal is to use these improved models and parameter estimates to model the climates of close-in orbiting exoplanets using planetary General Circulation Models (GCM). More specifically, we are working to apply our instellation corrections to the NASA ROCKE-3D GCM to study the climates of the potentially habitable planets in the Trappist-1 system. Full article

(This article belongs to the Proceedings of The 42nd International Workshop on Bayesian Inference and Maximum Entropy Methods in Science and Engineering)

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7 pages, 516 KB

Open AccessArticle

Non-Cosmological, Non-Doppler Relativistic Frequency Shift over Astronomical Distances

by Germano D’Abramo

Dynamics 2022, 2(3), 319-325; https://doi.org/10.3390/dynamics2030017 - 8 Sep 2022

Viewed by 2152

Abstract

We investigate in detail an apparently unnoticed consequence of special relativity. It consists in time dilation/contraction and frequency shift for emitted light affecting accelerated reference frames at astronomical distances from an inertial observer. The frequency shift is non-cosmological and non-Doppler in nature. We derive the main formulae and compare their predictions with the astronomical data available for Proxima Centauri. We found no correspondence with observations. Since the implications of the new time dilation/contraction and frequency shift are blatantly paradoxical, we do not expect to find one. By all indications, we are dealing with a genuine, and not a merely apparent, relativity paradox. Full article

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13 pages, 337 KB

Open AccessEditor’s ChoiceArticle

Effect of Some Modified Models of Gravity on the Radial Velocity of Binary Systems

by Lorenzo Iorio and Matteo Luca Ruggiero

Universe 2022, 8(9), 443; https://doi.org/10.3390/universe8090443 - 25 Aug 2022

Cited by 3 | Viewed by 2218

Abstract

For many classes of astronomical and astrophysical binary systems, long observational records of their radial velocity V, which is their directly observable quantity, are available. For exoplanets close to their parent stars, they cover several full orbital revolutions, while for wide binaries [...] Read more.

α

Centauri AB system, only relatively short orbital arcs are sampled by existing radial velocity measurements. Here, the changes

Δ V

induced on a binary’s radial velocity by some long-range modified models of gravity are analytically calculated. In particular, extra-potentials proportional to

r^{- N}, N = 2, 3

and

r^{2}

are considered; the Cosmological Constant

Λ

belongs to the latter group. Both the net shift per orbit and the instantaneous one are explicitly calculated for each model. The Cosmological Constant induces a shift in the radial velocity of the Proxima/

α

Centauri AB binary as little as

|Δ V| ≲ 10^{- 7} m s^{- 1}

, while the present-day accuracy in measuring its radial velocity is

σ_{V} ≃ 30 m s^{- 1}

. The calculational scheme presented here is quite general, and can be straightforwardly extended to any other modified gravity. Full article

(This article belongs to the Section Gravitation)

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