Centaurus A Research Articles

Editorial

The Alpha Centauri Scientific and Technological Research Journal is a peer-reviewed journal produced internationally, it is published QUARTERLY in online version ISSN: 2709-4502. Alpha Centauri publishes scientific articles specializing in Applied Social Sciences and Social Sciences in Information Technologies with great impact at an international level. We are currently trending in more than 24 countries disseminating Open Access scientific knowledge. IMAGES: Still images, audio recordings, video and related computer files for non-commercial use. NASA content (images, audio, video, and computer files used in the reproduction of three-dimensional models, such as texture maps and polygonal data in any format).

Improving Earth-like planet detection in radial velocity using deep learning

Context. Many novel methods have been proposed to mitigate stellar activity for exoplanet detection as the presence of stellar activity in radial velocity (RV) measurements is the current major limitation. Unlike traditional methods that model stellar activity in the RV domain, more methods are moving in the direction of disentangling stellar activity at the spectral level. As deep neural networks have already been proven to be one of the most effective tools in data mining, in this work, we explore their potential in the context of Earth-like planet detection in RV measurements. Aims. The goal of this paper is to present a novel convolutional neural network-based algorithm that efficiently models stellar activity signals at the spectral level, enhancing the detection of Earth-like planets. Methods. Based on the idea that the presence of planets can only produce a Doppler shift at the spectral level while the presence of stellar activity can introduce a variation in the profile of spectral lines (asymmetry and depth change), we trained a convolutional neural network to build the correlation between the change in the spectral line profile and the corresponding RV, full width at half maximum (FWHM) and bisector span (BIS) values derived from the classical cross-correlation function. Results. This algorithm has been tested on three intensively observed stars: Alpha Centauri B (HD 128621), Tau ceti (HD 10700), and the Sun. By injecting simulated planetary signals at the spectral level, we demonstrate that our machine learning algorithm can achieve, for HD 128621 and HD 10700, a detection threshold of 0.5 m s−1 in semi-amplitude for planets with periods ranging from 10 to 300 days. This threshold would correspond to the detection of a ~4 M⊕ in the habitable zone of those stars. On the HARPS-N solar dataset, thanks to significantly more data, our algorithm is even more efficient at mitigating stellar activity signals and can reach a threshold of 0.2 m s−1, which would correspond to a 2.2 M⊕ planet on the orbit of the Earth. Conclusions. To the best of our knowledge, it is the first time that such low detection thresholds are reported for the Sun, but also for other stars, and therefore this highlights the efficiency of our convolutional neural network-based algorithm at mitigating stellar activity in RV measurements.

Influence of ideas of Russian cosmism on formation and development of scientific and technical elite of rocket engineering and cosmonautics

The article is devoted to the influence of philosophical and theoretical ideas of the scientific direction of Russian cosmism on their transformation into a scientific and practical plane – the creation of the rocket and space industry, the launch of satellites, rockets, and humans into space. The relevance of the problem considered in the article lies in the fact that space, while remaining the sphere of interests of the leading world powers competing with each other in political, economic, cultural, and military terms, remains a platform for international cooperation, on which factors of national and global security largely depend. In this work, space exploration is considered in the development from philosophical and scientific research of the late 19th – early 20th century to projects of private corporations investing in the exploration of the Moon, colonization of Mars, development of a fleet of interstellar ships for travel to the Alpha Centauri system in our days. Scientific novelty is determined by a comprehensive consideration of the dialectics of the intellectual, creative and pragmatic in matters of space exploration. In a short period of time, under the influence of the philosophical ideas of the scientific direction of cosmism, and their logical continuation in the form of the development of the theory of cosmonautics and rocket science, there was the emergence of a new stratum of society – scientific and technical elite, which brought the country to a new level of technical development, which allows it to remain the world's leading space power to this day.

Testing quantized inertia on Proxima Centauri

ABSTRACT The Alpha Centauri system has two close stars Alpha and Beta (A & B) and one much further away: Proxima Centauri. All three stars are co-moving with similar chemistry, which implies they are bound, but the fast orbit of Proxima implies it is gravitationally unbound given the visible mass of A and B. This problem cannot be fixed with the addition of dark matter, which must be uniform on such scales, or adding mass to A and B (their mass is well constrained) or by Modified Newtonian Dynamics. A new model for inertia called Quantized Inertia (QI) has been proposed that solves the galaxy rotation problem by reducing the inertia of low-acceleration stars at the galaxies’ edge in a new way, thus keeping them bound without the need for dark matter. It is shown here that if QI is applied to Proxima Centauri in the same way, it predicts the observed orbital velocity, within the bounds of observational uncertainty, and binds Proxima, without the need for extra mass.

Нелинейная радиофизика межзвездных перелетов: разгон макрообъектов с помощью электромагнитного излучения

We discusses one of the implementations of acceleration, based on powerful artificial radiation, of spacecraft capable of reaching the nearest stars in the constellation Alpha Centauri in twenty to thirty years (i.e., during the active life of one generation of people). The Breakthrough Starshot project (BS, Breakthrough: Starshot) was proposed in 2016. The key new aspects of the project are: 1) the idea of interstellar vehicles of ultra-small dimension, which makes the physical parameters of the project potentially achievable in the foreseeable future; 2) modular construction of the launch system and 3) extension of Moore's law to the development of space technology. As an alternative to the linear “BS” type scheme, a closed ring scheme for laser acceleration of macro-objects is considered below. It is shown to be promising for dramatically reducing the peak requirements for a linear-type micro spacecraft launch.

Editorial

The Alpha Centauri Scientific and Technological Research Journal is a peer-reviewed journal produced internationally, it is published QUARTERLY in online version ISSN: 2709-4502. Alpha Centauri publishes scientific articles specializing in Applied Social Sciences and Social Sciences in Information Technologies with great impact at an international level. We are currently trending in more than 24 countries disseminating Open Access scientific knowledge. IMAGES: Still images, audio recordings, video and related computer files for non-commercial use. NASA content (images, audio, video, and computer files used in the reproduction of three-dimensional models, such as texture maps and polygonal data in any format).

Correction: Cuello, N.; Sucerquia, M. Alpha Centauri: Disc Dynamics, Planet Stability, Detectability. Universe 2024, 10, 64

In the original publication [...]

Alpha Centauri: Disc Dynamics, Planet Stability, Detectability

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⊕. 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.

Editorial

The Alpha Centauri Scientific and Technological Research Journal is a peer-reviewed journal produced internationally, it is published QUARTERLY in online version ISSN: 2709-4502. Alpha Centauri publishes scientific articles specializing in Applied Social Sciences and Social Sciences in Information Technologies with great impact at an international level. We are currently trending in more than 24 countries disseminating Open Access scientific knowledge. IMAGES: Still images, audio recordings, video and related computer files for non-commercial use. NASA content (images, audio, video, and computer files used in the reproduction of three-dimensional models, such as texture maps and polygonal data in any format).

Fe ii fluorescence in main-sequence K-dwarfs

ABSTRACT Main-sequence K-dwarfs possess strong emission in the form of the H i Ly α line. There is a close coincidence between the energy corresponding to the transitions H i 1s-2p and Fe ii (5D)5s 4D5/2–(5D)5p 4D5/2. Singly ionized iron has been confirmed being pumped by photo-excitation by accidental resonance (PAR) in planetary nebulae, symbiotic stars, K-giants, and active galactic nebulae. I investigate in this work whether PAR can occur in the atmospheres of main-sequence K-dwarfs, which do not possess the large extended atmospheres of the late-type K-giants. Specifically a search for possible Fe ii fluorescence lines is conducted. For the case when I can confirm PAR, I estimate the total flux leaving the stars in the form of Fe ii fluorescence. I search for emission lines from the Fe ii (5D)5p 4D5/2 level. Since those of these lines with the largest branching fractions correspond to lines at wavelengths covered by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, a search for archival FUSE spectra from K-dwarfs within 20 ly from the sun is conducted. I retrieve and analyse FUSE spectra for four of these K-dwarfs. In each case I can confirm PAR, I fit the H i Ly α line in Hubble Space Telescope spectra recorded with the Space Telescope Imaging Spectrograph, in order to estimate the efficiency of the PAR mechanism. I can now confirm Fe ii fluorescence in the two closest K-dwarfs, Alpha Centauri B, and Epsilon Eridani. The total power leaving as Fe ii fluorescence are 4.9 × 1017 and 1.30 × 1018 W respectively.

Calculations of Particle Bombardment Due to Dust and Charged Particles in the ISM on the Project Starshot Gram-Scale Interstellar Probe

The Breakthrough Initiatives Project Starshot proposes to send a gram-scale laser driven spacecraft to the Alpha Centauri system in a 20 year mission travelling at v~0.2c. One of the challenges of this mission as the spacecraft moves through the interstellar medium is the presence of dust and gas (mostly hydrogen). The dust has a typical matter-density of 2.57 × 10-27 g/cm3 with typical particle mass being 3 × 10-13 g although some of the largest particles may be 5 × 10-9 g in mass. These dust particles will deposit ~1012-1016 MeV onto the spacecraft with an energy flux of order ~0.3 J/sm2. We consider the erosion of the spacecraft frontal area due to dust and also heating effects. We attempt to characterise the likely environment for the Starshot mission and estimate the particle bombardment shielding requirements in terms of mass and thickness of material. Current analysis estimates that the likely erosion rates are of order ~10-11-10-8 g/s and that the frontal area temperature for the models examined in this paper will be ~135.2 K depending on the ratio of frontal area to radiating area. For an assumed shielding material with atomic number range 3-13 (Lithium to Aluminium), and for spacecraft geometries with radii ~1 mm and cylindrical length ~5 mm, over a 21.5 year mission duration, this would suggest a shielding thickness of ~1.4-3 mm. This would also suggest a shielding mass in the range ~0.01-0.05 g; depending on the material choice, spacecraft size and chosen geometry. This would represent between ~1–5% of the total mass, assuming a spacecraft mass of 1g (driven by a ~102 GW laser power). We also examine the additional effects of charged particles and estimate the stopping power and penetration range for different materials. Finally, we briefly examine the potential to use the incoming energy flux as a power source for the transmission of an optical laser deep space communication system. The work presented highlights the close coupling in the Project Starshot spacecraft design between the vehicle geometry and the particle bombardment requirements.

The Cycles of Alpha Centauri: Double Dipping of AB

Abstract In mid-2023, the Sunlike dwarfs of nearby α Centauri (HD 128620 (“A”): G2 V; HD 128621 (“B”): K1 V; hereafter “AB”) coincidentally both entered coronal (T ≈ 1–3 MK) low states in their long-term X-ray cycles, as captured by the Chandra Observatory and its High Resolution Camera (HRC-I). The assessment benefited from a sensitivity degradation model for HRC-I based on a “check star,” the F subgiant Procyon (α Canis Minoris A; HD 61421: F5 IV–V), further validated by Hubble Space Telescope time series of the Fe xii 1241.985 Å and 1349.396 Å coronal forbidden lines (T ≈ 1.6 MK) of all three stars. The AB starspot-cycle periods noted previously, 19 and 8 yr, appear to be holding. These deviate substantially from the 11 yr solar example, despite only modest differences in the stellar properties. The new cycle-minimum L X/L BOL of α Cen A is similar to that of the previous minimum observed by Chandra in 2005–2010, and close to solar-MIN X-ray levels in 2009 and 2019, with implications for the “basal” coronal flux of low-activity early G stars. The recent α Cen B X-ray MIN is similar to that in 2016 but higher than an earlier one in 2007–2009. Significantly, the B X-ray minima (in L X/L BOL) are comparable to the solar Cycle 24 maximum, suggesting plentiful starspots at the B-cycle MIN (contrary to the solar case). Tangentially, the current AB low states favor Doppler-reflex detections of planets, as opposed to the coronal high states, when elevated chromospheric activity can add nuisance signals to radial velocity time series.

Fortuitous Observations of Potential Stellar Relay Probe Positions with GBT

Recent theoretical and observational works have investigated the possibility that extraterrestrial intelligence could use the Sun as a gravitational lens in order to aid communication across interstellar distances. Unlike other targeted SETI searches where the drift rate of any artificial extraterrestrial signals may be unknown up to some large upper limit, the drift rates of any solar system relay probes would be known and set only by the motion of the Earth. One recent work used purpose-designed Green Bank Telescope (GBT) observations to search for signals from a hypothetical communications probe several hundred astronomical unit from the Sun at the antipode of the α Centauri AB system. To further aid in the advancement of relay-probe searches, we present a table of 1764 archival GBT observations which fortuitously fall near the positions of hypothetical probes communicating with stars within 100 pc and compute the drift rates for these probes.

From exo-Earths to exo-Venuses: Flux and polarization signatures of reflected light

Context. Terrestrial-type exoplanets in or near stellar habitable zones appear to be ubiquitous. It is, however, unknown which of these planets have temperate, Earth-like climates or for example, extreme Venus-like climates. Aims. Technical tools to distinguish different kinds of terrestrial-type planets are crucial for determining whether a planet could be habitable or incompatible with life as we know it. We aim to investigate the potential of spectropolarimetry for distinguishing exo-Earths from exo-Venuses. Methods. We present numerically computed fluxes and degrees of linear polarization of starlight that is reflected by exoplanets with atmospheres in evolutionary states ranging from similar to the current Earth to similar to the current Venus, with cloud compositions ranging from pure water to 75% sulfuric acid solution, for wavelengths between 0.3 and 2.5 µm. We also present flux and polarization signals of such planets in stable but spatially unresolved orbits around the star Alpha Centauri A. Results. The degree of polarization of the reflected starlight shows larger variations with the planetary phase angle and wavelength than the total flux. Across the visible, the largest degree of polarization is reached for an Earth-like atmosphere with water clouds due to Rayleigh scattering above the clouds and the rainbow feature at phase angles near 40°. At near-infrared wavelengths, the planet with a Venus-like CO2 atmosphere and thin water cloud shows the most prominent polarization features due to Rayleigh-like scattering by the small cloud droplets. A planet in a stable orbit around Alpha Centauri A would leave temporal variations on the order of 10−13 W m s−1 in the total reflected flux and 10−11 in the total degree of polarization as the planet orbits the star and assuming a spatially unresolved star-planet system. Star-planet contrasts are on the order of 10−10 and vary proportionally with planetary flux. Conclusions. Current polarimeters appear to be incapable to distinguish between the possible evolutionary phases of spatially unresolved terrestrial exoplanets, as a sensitivity close to 10−10 would be required to discern the planetary signal given the background of unpolarized starlight. A telescope or instrument capable of achieving planet-star contrasts lower than 10−9 should be able to observe the large variation of the planets resolved degree of polarization as a function of its phase angle and thus be able to discern an exo-Earth from an exo-Venus based on their clouds unique polarization signatures.

Analyzing the engineering feasibility of the direct fusion drive

The Direct Fusion Drive (DFD) and its terrestrial counterpart, the Princeton Field Reversed Configuration (PFRC) reactor, have seen significant developments in the past decade. Various groups conducted detailed research on the required specifications of the engine and associated technology for power delivery to onboard avionics and payloads. Multiple studies have also addressed the thrust generation mechanism using empirical specific power scaling relations and plasma flow simulations. Recent studies have designed spacecraft for missions to Earth’s second Lagrange point, Mars, transneptunian bodies like Pluto, and the neighboring star systems Alpha Centauri A and B. However, significant work is needed to design the engine components in detail using scientific scaling relations and ab inito calculations to develop the physical systems for prototyping and testing. After critically analyzing the reference design of the DFD and the underlying fusion reactor, this paper addresses the technological gaps and suggests avenues to improve specifications toward targets outlined in previous studies while considering costs. Further, the authors present a prototype engine and magnetohydrodynamic power conversion system design to study the engineering hurdles relevant to the practical implementation of the DFD.

Simulation of the Earth’s radio-leakage from mobile towers as seen from selected nearby stellar systems

ABSTRACT Mobile communication towers represent a relatively new but growing contributor to the total radio-leakage associated with planet Earth. We investigate the overall power contribution of mobile communication towers to the Earth’s radio leakage budget, as seen from a selection of different nearby stellar systems. We created a model of this leakage using publicly available data of mobile tower locations. The model grids the surface of the planet into small, computationally manageable regions, assuming a simple integrated transmission pattern for the mobile antennas. In this model, these mobile tower regions rise and set as the Earth rotates. In this way, a dynamic power spectrum of the Earth was determined, summed over all cellular frequency bands. We calculated this dynamic power spectrum from three different viewing points – HD 95735, Barnard’s star, and Alpha Centauri A. Our preliminary results demonstrate that the peak power leaking into space from mobile towers is ∼4GW. This is associated with Long Term Evolution (LTE) mobile tower technology emanating from the East Coast of China as viewed from HD 95735. We demonstrate that the mobile tower leakage is periodic, direction dependent, and could not currently be detected by a nearby civilization located within 10 light-years of the Earth, using instrumentation with a sensitivity similar to the Green Bank Telescope. We plan to extend our model to include more powerful 5G mobile systems, radar installations, ground based up-links (including the Deep Space Network), and various types of satellite services, including low-Earth orbit constellations, such as Starlink and OneWeb.

Re-Distribution of the Regions of 100 Comets Using a Statistical Method

In this study, the comets have distributions regarding their heliocentric distances where they appear in two regions, Kuiper belt (short period) and Oort cloud (long period). Details here give new information about the entire regions of these comets; the research shows that 54% of comets are nearby asteroid belt, but only 11% are in Kuiper belts and 35 % are from Oort cloud. The research focuses on comets with a nucleus's radius larger than 1 km. The comets with a nuclear radius of 1-10 km have high percentage 51%. From the results, the maximum comets' radius is found in comet 29P/Schwassmann -Wachmann as roughly 87 km, and also in comet C/2018 N2 (ASASSN) which has radius 88 km. All comets, that have been distributed concerning heliocentric, depend on statistical results to divide new comets' regions versus their radiuses. The results reveal new details of comets' distances from the sun. The distances of 100 comets are shown in Figure (2). The results show that there is a third comets' region: region (A) found between Mars and Saturn and between Oort cloud and Kuiper belt. There is one comet like(C/2019 L3 (ATLAS)) that is farther than Alpha Centauri star. Therefore, the comet is restricted by a couple of gravity systems.

A Search for Radio Technosignatures at the Solar Gravitational Lens Targeting Alpha Centauri

Stars provide an enormous gain for interstellar communications at their gravitational focus, perhaps as part of an interstellar network. If the Sun is part of such a network, there should be probes at the gravitational foci of nearby stars. If there are probes within the solar system connected to such a network, we might detect them by intercepting transmissions from relays at these foci. Here, we demonstrate a search across a wide bandwidth for interstellar communication relays beyond the Sun’s innermost gravitational focus at 550 au using the Green Bank Telescope (GBT) and Breakthrough Listen (BL) backend. As a first target, we searched for a relay at the focus of the Alpha Centauri AB system while correcting for the parallax due to Earth’s orbit around the Sun. We searched for radio signals directed at the inner solar system from such a source in the L and S bands. Our analysis, utilizing the turboSETI software developed by BL, did not detect any signal indicative of a non-human-made artificial origin. Further analysis excluded false negatives and signals from the nearby target HD 13908. Assuming a conservative gain of 103 in the L band and roughly 4 times that in the S band, a ∼1 m directed transmitter would be detectable by our search above 7 W at 550 au or 23 W at 1000 au in the L band, and above 2 W at 550 au or 7 W at 1000 au in the S band. Finally, we discuss the application of this method to other frequencies and targets.

Simulations of astrometric planet detection in Alpha Centauri by intensity interferometry

ABSTRACT Recent dynamical studies indicate that the possibility of an Earth-like planet around α Cen A or B should be taken seriously. Such a planet, if it exists, would perturb the orbital astrometry by $\lt {10}\, {\mu {\rm as}}$, which is 10−6 of the separation between the two stars. We assess the feasibility of detecting such perturbations using ground-based intensity interferometry. We simulate a dedicated set-up consisting of four 40-cm telescopes equipped with photon counters and correlators with a time resolution of $0.1\, \rm ns$, and a sort of matched filter implemented through an aperture mask. The astrometric error from one night of observing α Cen AB is $\approx 0.5\, \rm mas$. The error decreases if longer observing times and multiple spectral channels are used, as (channels × nights)−1/2.

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

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 such as, e.g., the Proxima/α Centauri AB system, only relatively short orbital arcs are sampled by existing radial velocity measurements. Here, the changes ΔV 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 r2 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 ΔV≲10−7ms−1, while the present-day accuracy in measuring its radial velocity is σV≃30ms−1. The calculational scheme presented here is quite general, and can be straightforwardly extended to any other modified gravity.