Astronomical Systems Research Articles

The Mueller pupils Reduction-Zernike polynomial decomposition and polarization design criteria for the astronomical telescope system

This study introduces a novel method for decomposing polarization aberrations. It uses two sets of reduction matrices to decompose the diattenuation and retardance Mueller matrix into five independent reduction coefficients. And then, it uses Zernike polynomials to decompose these coefficients at the exit pupil, thereby providing a method for quantitatively analyzing the polarization aberrations. This method also gives the constraint values of the Zernike term of polarization aberrations during astronomical telescope design. Finally, the effectiveness and correctness of the process are verified by simulation of the actual optical system, pointing out that the D1, D2, D3, and R5 terms need to be calibrated and optimized to ensure polarization accuracy. This method offers a valuable tool and theoretical guidance for the polarization design of high-precision optical systems.

Pathfinding Pulsar Observations with the CVN Incorporating the FAST

Abstract The importance of Very Long Baseline Interferometry (VLBI) for pulsar research is becoming increasingly prominent and receiving more and more attention. We present the pathfinding pulsar observation results with the Chinese VLBI Network (CVN) incorporating the Five-hundred-meter Aperture Spherical radio Telescope (FAST). On MJD 60045 (11th April 2023), PSRs B0919+06 and B1133+16 were observed with the phase-referencing mode in the L-band using four radio telescopes (FAST, TianMa, Haoping, and Nanshan) and correlated with the pulsar binning mode of the distributed FX-style software correlator in Shanghai. After further data processing with the NRAO Astronomical Image Processing System (AIPS), we detected these two pulsars and fitted their current positions with accuracy at the milliarcsecond level. By comparison, our results show significantly better agreement with predicted values based on historical VLBI observations than those with previous timing observations, as pulsar astrometry with the VLBI provides a more direct and model-independent method for accurately obtaining related parameters.

When the Anomalistic, Draconitic and Sidereal Orbital Periods Do Not Coincide: The Impact of Post-Keplerian Perturbing Accelerations

In a purely Keplerian picture, the anomalistic, draconitic and sidereal orbital periods of a test particle orbiting a massive body coincide with each other. Such degeneracy is removed when post-Keplerian perturbing acceleration enters the equations of motion, yielding generally different corrections to the Keplerian period for the three aforementioned characteristic orbital timescales. They are analytically worked out in the case of the accelerations induced by the general relativistic post-Newtonian gravitoelectromagnetic fields and, to the Newtonian level, by the oblateness of the central body. The resulting expressions hold for completely general orbital configurations and spatial orientations of the spin axis of the primary. Astronomical systems characterized by extremely accurate measurements of orbital periods like transiting exoplanets and binary pulsars may offer potentially viable scenarios for measuring such post-Keplerian features of motion, at least in principle. As an example, the sidereal period of the brown dwarf WD1032 + 011 b is currently known with an uncertainty as small as ≃10−5s, while its predicted post-Newtonian gravitoelectric correction amounts to 0.07s; however, the accuracy with which the Keplerian period can be calculated is just 572 s. For double pulsar PSR J0737–3039, the largest relativistic correction to the anomalistic period amounts to a few tenths of a second, given a measurement error of such a characteristic orbital timescale as small as ≃10−6s. On the other hand, the Keplerian term can be currently calculated just to a ≃9 s accuracy. In principle, measuring at least two of the three characteristic orbital periods for the same system independently would cancel out their common Keplerian component, provided that their difference is taken into account.

Utilizing Voronoi Tessellations to Determine Radial Density Profiles

We have developed a novel method of determining 2D radial density profiles for astronomical systems of discrete objects using Voronoi tessellations. This Voronoi-based method was tested against the standard annulus-based method on five simulated systems of objects, following known Hubble density profiles of varying parameters and sizes. It was found that the Voronoi-based method returned radial density fits with lower uncertainties on the fitting parameters across all five systems compared to the annulus-based method. The Voronoi-based method also consistently returned more accurate estimates of the total number of objects in each system than the annulus-based method, and this accuracy increased with increasing system size. Finally, the Voronoi-based method was applied to two observed globular cluster systems around brightest cluster galaxies ESO 444-G046 and 2MASX J13272961-3123237 and the results were compared to previous results for these galaxies obtained with the annulus-based method. Again, it was found that the Voronoi-based method returned fits with lower uncertainties on the fitting parameters, and the total number of globular clusters returned are within errors of the annulus-based method estimates, however also with lower uncertainties.

Discovery and Classification in Astronomy: Scientific and Philosophical Challenges and the Importance of a Comprehensive and Consistent Classification System

Throughout history, the definition of “class” and the construction of astronomical classification systems has been a deep scientific and philosophical problem: scientific because facts such as physical composition ideally need to be known for proper classification but often are not, philosophical because astronomers need to understand the philosophical assumptions behind their attempts at classification, and because different philosophical ideas such as “natural kinds” often guide classification, even if unconsciously. The primary lesson of history is that the most useful classifications of celestial objects are optimally based on their physical nature. The second lesson is that because discovery is an extended process consisting of detection, interpretation, and understanding, initial classifications may be phenomenological, based on characteristics that may be useful in early “detection” stages of extended discovery. By contrast, final classifications of “the thing itself,” is achieved only after the “understanding” stage of discovery and must have a physical basis. A third lesson is that class status is best determined within a comprehensive classification system in order to determine taxon level, e.g., class, type, subtype. Such a system, encompassing all astronomical objects, illustrates the problems of class and classification, problems that may be applied to exoplanet discoveries.

Conformer-Specific Photoelectron Spectroscopy of Carbonic Acid: H2CO3.

Carbonic acid (H2CO3) is a fundamental species in biological, ecological, and astronomical systems. However, its spectroscopic characterization is incomplete because of its reactive nature. The photoionization (PI) and the photoion mass-selected threshold photoelectron (ms-TPE) spectra of H2CO3 were obtained by utilizing vacuum ultraviolet (VUV) synchrotron radiation and double imaging photoelectron photoion coincidence spectroscopy. Two carbonic acid conformers, namely, cis-cis and cis-trans, were identified. Experimental adiabatic ionization energies (AIEs) of cis-cis and cis-trans H2CO3 were determined to be 11.27 ± 0.02 and 11.18 ± 0.03 eV, and the cation enthalpies of formation could be derived as ΔfH°0K = 485 ± 2 and 482 ± 3 kJ mol-1, respectively. The cis-cis conformer shows intense peaks in the ms-TPES that are assigned to the C=O/C-OH stretching mode, while the cis-trans conformer exhibits a long progression to which two C=O/C-OH stretching modes contribute. The TPE spectra allow for the sensitive and conformer-selective detection of carbonic acid in terrestrial experiments to better understand astrochemical reactions.

Impact of Al Durror App in Preserving Astronomical Timekeeping and Cultural Sustainability

In an era where the digital transformation is reshaping every facet of life, the preservation of cultural heritage through smart technologies emerges as a crucial endeavor. This research paper delves into the innovative intersection of traditional knowledge and modern technology, focusing on the Al Durror smart application, a digital tool designed to preserve and promote the Al Durror Calendar. This ancient astronomical timekeeping system, deeply ingrained in the cultural fabric of the Gulf region, is a testament to the rich historical and astronomical wisdom of its people. The Al Durror Calendar, structured around the annual rising of the Suhail star, divides the year into thirty-six decadal sections, each known as “Al- Durr,” forming a unique chronological framework integral to the region's cultural identity. The study embarks on a comprehensive evaluation of the Al Durror app, launched a decade ago, and its role in the digital preservation of this ancient calendar. With over 100,000 downloads and a dedicated user base of 20,000, the app not only serves as a digital repository of the Al Durror Calendar but also as a platform for cultural engagement and education. The research aims to assess the app's effectiveness in fostering a deeper understanding and appreciation of this traditional timekeeping system among contemporary audiences. It explores the app's usage patterns, user engagement, and its impact on the revival of the Al Durror Calendar in daily life.

Pupil calibration for pyramid wavefront sensors based on a wavefront corrector.

The pyramid wavefront sensor (PWS) presents numerous advantages, such as high energy utilization, exceptional spatial resolution, and adjustability. Precise calibration of the pupil's position and size in advance is essential for accurately extracting wavefront slope information from the captured pupil image by the PWS. What we believe to be a novel calibration method is proposed using a wavefront corrector to enhance the sharpness of the pupil images in the PWS. An experimental setup using a crystal spatial light modulator (SLM) is established to validate this method. Both physical experiments and simulated results demonstrate that our proposed method can achieve accurate calibration of the pupil image with an error within 4 pixels for pupil size and not exceeding 3 pixels for position, meeting practical application requirements. The proposed PWS calibration method exhibits excellent repeatability and robustness, making it directly applicable in astronomical adaptive optics systems.

ON THE CORRECT COMPUTATION OF ALL LYAPUNOV EXPONENTS IN HAMILTONIAN DYNAMICAL SYSTEMS

The Lyapunov characteristic exponents are a useful indicator of chaos in astronomical dynamical systems. They are usually computed through a standard, very effcient and neat algorithm published in 1980. However, for Hamiltonian systems the expected result of pairs of opposite exponents is not always obtained with enough precision. We find here why in these cases the initial order of the deviation vectors matters, and how to sort them in order to obtain a correct result.

Alert Classification for the ALeRCE Broker System: The Anomaly Detector

Astronomical broker systems, such as Automatic Learning for the Rapid Classification of Events (ALeRCE), are currently analyzing hundreds of thousands of alerts per night, opening up an opportunity to automatically detect anomalous unknown sources. In this work, we present the ALeRCE anomaly detector, composed of three outlier detection algorithms that aim to find transient, periodic, and stochastic anomalous sources within the Zwicky Transient Facility data stream. Our experimental framework consists of cross-validating six anomaly detection algorithms for each of these three classes using the ALeRCE light-curve features. Following the ALeRCE taxonomy, we consider four transient subclasses, five stochastic subclasses, and six periodic subclasses. We evaluate each algorithm by considering each subclass as the anomaly class. For transient and periodic sources the best performance is obtained by a modified version of the deep support vector data description neural network, while for stochastic sources the best results are obtained by calculating the reconstruction error of an autoencoder neural network. Including a visual inspection step for the 10 most promising candidates for each of the 15 ALeRCE subclasses, we detect 31 bogus candidates (i.e., those with photometry or processing issues) and seven potential astrophysical outliers that require follow-up observations for further analysis. 16 16 The code and the data needed to reproduce our results are publicly available at https://github.com/mperezcarrasco/AnomalyALeRCE.

Aristotle as an Astronomer? Sosigenes’ Account of Metaphysics Λ.8

Abstract I have argued elsewhere that the idea that Aristotle aspired to improve the theories of the planetary motions of Eudoxus and Callippus by adding the ‘counteracting’ spheres (ἀνελίττουσαι) first emerged with the Peripatetic exegete Sosigenes in the second century CE. This paper supplements that argument by contrasting two major lines of interpretation of the astronomical system set out in Metaphysics Λ.8: Adrastus of Aphrodisias’ widely ahistorical account, and Sosigenes’ attempt to save Aristotle against later developments of astronomical science.

Internal kinematics of Gaia DR3 wide binaries: anomalous behaviour in the low acceleration regime

ABSTRACT The Gaia eDR3 catalogue has recently been used to study statistically the internal kinematics of wide binary populations using relative velocities of the two component stars, ΔV, total binary masses, mB, and separations, s. For s ≳ 0.01 pc, these binaries probe the low-acceleration a ≲ 2a0 regime where gravitational anomalies usually attributed to dark matter are observed in the flat rotation curves of spiral galaxies, where a0 ≈ 1.2 × 10−10 m s−2 is the acceleration scale of MOND. Such experiments test the degree of generality of these anomalies, by exploring the same acceleration regime using independent astronomical systems of vastly smaller mass and size. A signal above Newtonian expectations has been observed when a ≲ 2a0, alternatively interpreted as evidence of a modification of gravity, or as due to kinematic contaminants; undetected stellar components, unbound encounters, or spurious projection effects. Here I take advantage of the enhanced DR3 Gaia catalogue to perform a more rigorous study of the internal kinematics of wide binaries than what has previously been possible. Internally determined Gaia stellar masses and estimates of binary probabilities for each star using spectroscopic information, together with a larger sample of radial velocities, allow for a significant improvement in the analysis and careful exclusion of possible kinematic contaminants. Resulting ΔV scalings accurately tracing Newtonian expectations for the high acceleration regime, but markedly inconsistent with these expectations in the low acceleration one, are obtained. A non-Newtonian low acceleration phenomenology is thus confirmed.

New opportunities for astronomical imaging systems

AbstractThis paper will look at two significant technological developments, one concerning the performance of optical and infrared detector systems, which are now capable of genuine photon counting performance, and secondly a new approach to tackling the problem of adaptive optics when only faint reference stars are available close to the target object.

Astronomical Camera Based on a CCD261-84 Detector with Increased Sensitivity in the Near-Infrared

Herein, we describe the design, implementation and operation principles of an astronomical camera system, based on a large-format CCD261-84 detector with an extremely thick 200 μm substrate. The DINACON-V controller was used with the CCD to achieve high performance and low noise. The CCD system photometric characteristics are presented. A spatial autocorrelation analysis of flat-field images was performed to reveal the dependence of substrate voltage on the lateral charge spreading. The investigation of the dispersion index for the optimal choice of exposure time is discussed. Studies of the patterns of fringes were carried out in comparison with previous detectors. The amplitude of fringes with CCD261-84 was significantly lower, compared to previous-generation detectors. The results of using a new camera for imaging and spectral observations at the Russian 6 m telescope with the SCORPIO-2 multimode focal reducer are considered. The developed CCD camera system makes it possible to significantly increase the sensitivity in the 800–1000 spectral range.

Astronomical inertial systems for use in marine navigation complexes

Astronomical means of navigation for solving applied tasks with a long duration of execution, their advantages in comparison with other sources of navigation information are considered. The prerequisites for the creation of a new generation of astrogation systems are analyzed. The layout of the astrogation system, its components, appearance and internal structure are presented. The functional scheme of the system for various operating modes is given. The limitations on the use of astrosystems in marine conditions and ways to overcome them when designing an experimental sample are shown. The test results of the experimental sample allowed us to determine the directions for further improvement of the design and characteristics of new-generation astrogation systems.

A Method of Superimposing Subapertures for Shark–Hartmann Wave Front Sensing with Faint Objects

Abstract For the astronomical adaptive optics systems, the observation condition is always in a regime of low photon flux. We present a method of superimposing subapertures for the Shark–Hartmann wave front sensing with faint objects. This approach significantly improves the signal-to-noise ratio (S/N) of the spot pattern by superimposing adjacent subapertures, thus circumventing the invalid wave front sensing with faint object, enhancing the accuracy of the wave front detection. In addition, we demonstrate that the validity of this approach is not an incidental result under a specific condition, which can be explained theoretically by exploiting the atmospheric turbulence model. Then we validate the approach with simulations and experimental realization under weak-light and bright-light conditions. Results show that the proposed subaperture superposition approach can achieve accurate wave front reconstruction for low S/N or faint object even in cases beyond the ability of conventional methods. It brings out a new idea, besides long exposure and variable sampling, that comes with a tradeoff between temporal sampling frequency and spatial resolution. In addition, this method is also valid for extended objects; we preliminarily validate this method on a 600 mm aperture solar telescope, achieving stable closed-loop control with lower-contrast objects.

Meteor cluster event indication in variable-length astronomical video sequences

Abstract In recent years, the study of parallel or cluster meteor events has become increasingly popular. Many imaging systems currently focus on meteor detection, but the algorithms exploiting the data from such systems do not investigate the probability of cluster or parallel meteor events. This paper presents a novel approach to indicate a potential meteor cluster or parallel meteor event based on variable-length astronomical video sequences. The presented algorithm consists of two main parts: meteor event pre-detection and meteor cluster event probability evaluation. The first part of the algorithm involves a meteor pre-detection method based on the Hough transform (HT) and the exact event location within the time domain. In addition to pre-detecting meteor events, the method outputs event trajectory parameters that are further exploited in a second part of the algorithm. This subsequent part of the algorithm then operates over these meteor trajectory parameters and indicates the probability of cluster occurrence. The algorithm is experimentally evaluated on video sequences generated by the Meteor Automatic Imager and Analyzer (MAIA) astronomical imaging system, covering the Draconid and September ε Perseid (SPE) meteor showers. Compared to the current MAIA meteor detection software, the proposed part of the pre-detection algorithm shows promising results, especially the increased rate of correct meteor detection. The meteor cluster evaluation part of the algorithm then demonstrates its ability to successfully select related meteor event candidates (disintegrated from the same parental object) and reject unrelated ones.

The principle of relativity from the organisational point of view1

AbstractEinstein's special and general theories of relativity are explained and clarified when they are expressed in terms of the organisational principles of degression (the operation of stable ‘skeletal’ forms that humanity has worked out in its practice to organise less stable ‘plastic’ elements)—in this case, frameworks for spatial and temporal orientation—and degression (the operation of complexes that perform a centralising function in a given system), in this case, the concept of centres of gravity of astronomical systems.

Analysis of stability of non-collinear equilibrium points: Application to Sun–Mars and Proxima Centauri systems

In the present work, we employ the modified elliptic restricted three-body problem by considering some additional perturbed forces such as: the radiation pressure, the primaries’ oblateness, and the effect of dust belt for studying the dynamical motion of the infinitesimal body. The semi-analytical solutions for the locations of non-collinear equilibrium points are obtained. The proposed model is applied to real astronomical systems. Thus, the Sun–Mars and the Proxima Centauri systems are used to estimate numerically and graphically the locations of these points in both systems at different values of perturbation parameters. In this context, the critical mass values are evaluated for both systems to analyze the stability motion of the infinitesimal body around the locations of equilibrium points and find the stability range of these locations. We demonstrate that the stability of non-collinear points in both systems depends on the parameter of mass ratio values of its own system. It is observed that the locations of these points and their stability will be affected significantly due to the changes in the values of perturbation parameters.

Differences of Salat Time Recording: Analytical Contemporary Method of Kitab al-Khulashah al-Wafiyyah

The discussion on the reckoning of prayer times contained in the Khulashah book has its own characteristics. The initial calculation process for prayer times has referred to the triangular ball algorithm system. Besides, there are also daqoiqut tamkin corrections presented through tables, and calculation methods using calculators. This interesting calculation can be studied; how is the transformation system of prayer time coordinates and how is the accuracy level of the results of the initial prayer time calculation. This study uses a library research paradigm with a qualitative theory verification approach using an arithmetic approach and the results are presented descriptively, then compared with similar methods. The results show that the coordinate transformation has referred to the modern astronomical system and the calculation system has used spherical trigonometry (spherical triangle). The calculation results have differences ranging from 0 to 3 minutes with contemporary methods. It is caused by differences in data and methods. If the calculation using the contemporary method there is a difference of 0 seconds to 12 seconds, this indicates that when the calculation is made modifications to the contemporary calculation system will produce a more accurate calculation.