Subjects: Astronomy >> History of Astronomy Subjects: Other Disciplines >> Synthetic discipline submitted time 2024-06-27
Abstract: The Dasong Tianwenshu was compiled by the Bureau of Astronomy under imperial edict during the Yuanfeng era of the Northern Song Dynasty. Its overall structure is rigorous and well-organized, with certain volumes exhibiting innovative content, thus providing significant theoretical and practical value. Currently, there are three extant versions of this book: the National Museum version, the Shanghai Library version, and the Nanjing Library version. The latter two are more closely related in terms of textual lineage. The authors of this book include Wang Anli and Ouyang Fa, among others. The primary purpose of its compilation was to resolve the inconsistencies in divinatory statements found in contemporary divination texts, aiming for a standardized system that would facilitate divinatory practices. This study finds that Ouyang Fa and his colleagues used the Jingyou Qianxiang Xinshu as their main source, selectively incorporating, simplifying, and integrating various divinatory statements to form a new astrological text. Throught investigation of the the citation by historical documents, it can be determined that this book was known as the Song Tianwenzhi during the Jin Dynasty and played an important role in astronomical institutions during the Yuan and Ming Dynasties. The fifteen-volume Lingtai Miyuan was primarily based on this book, rather than being the original work of Yu Jicai from the Northern Zhou Dynasty. The Dasong Tianwenshu preserves many unique astronomical records from the Northern Song period, such as those related to the armillary sphere, star charts, gnomen, and clepsydra. These records hold significant historical value.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> History of Astronomy Subjects: Geosciences >> Atmospheric Sciences submitted time 2024-06-14
Abstract: This article describes another important driving force behind the Earth’s atmosphere and climate change; In addition to the geological activities of the Earth itself and foreign substances such as meteorites and comets, light gases and liquid water on Mercury and Venus are also important sources. This article only uses the basic knowledge of astronomy, basic physics, and chemical concepts to analyze how water and some gaseous substances in the Earth’s orbit reach the Earth under the action of the solar wind. It also analyzed how the light gas and liquid water on Mercury and Venus were transferred to Earth. The mechanism by which ecological atmospheres appear in stellar systems similar to the solar system was analyzed.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-06-14
Abstract: In this paper, the gravitational lensing of a static neutron star with magnetic moment and magnetic charge is studied. In the spacetime of such a neutron star, the deflection angle of a photon is directly proportional to the neutron star’s magnetic charge and mass-to-distance ratio, while inversely proportional to the magnetic moment of the neutron star. Specifically, when the magnetic charge is 0.5, the deflection angle is constant, independent of changes in the magnetic moment. When both the magnetic moment and the magnetic charge approach zero, all parameters revert to the Schwarzschild case.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science submitted time 2024-06-09
Abstract: The precise estimation of the satellite clock bias (SCB) holds considerable importance in ensuring accurate timekeeping, navigation, and positioning. This studyintroduces a novel SCB prediction approach that integrates variational mode decomposition (VMD) and long short-term memory (LSTM) network techniques, combining signal decomposition with deep learning methodologies. Initially, the raw SCB data undergoespreprocessing, followed by decomposition using the VMD method to generate multiple intrinsic mode functions (IMFs). These decomposed IMFs serve as inputs for LSTM, where several independent LSTM models are established for training and prediction purposes. Subsequently, the predicted outcomes are aggregated and reconstructed to derive the finalSCB prediction. Experimental findings demonstrate notable advancements in clock bias prediction for the spaceborne hydrogen atomic clock for BDS, with prediction accuracies of 0.048 ns, 0.204 ns and 1.397 ns for 6 hours, 3 days and 15 days, respectively. These results exhibit significant enhancements compared to both the LSTM network and the Back Propagation (BP) neural network, with improvements of 56%, 84% and 83% for the aforementioned time intervals in comparison to LSTM, and enhancements of 59%, 82% and 83% relative to the BP neural network.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2024-06-08
Abstract: In this work, we investigate configuration formation of two inner terrestrial planets near mean motion resonance (MMRs) induced by the perturbation of a distant gas-giant for the Kepler-68 system, by conducting thousands of numerical simulations. The results show that the formation of terrestrial planets is relevant to the speed of Type I migration, the mass of planets, and the existence of giant planet. The mass and eccentricity of the giant planet may play a crucial role in shaping the final configuration of the system. The inner planet pair can be trapped in 5:3 or 7:4 MMRs if the giant planet revolves the central star with an eccentric orbit, which is similar to the observed configuration of Kepler-68. Moreover, we find that the eccentricity of the middle planet can be excited to roughly 0.2 if the giant planet is more massive than 5 $M_J$,otherwise the terrestrial planets are inclined to remain near-circular orbits. Our study may provide a likely formation scenario for the planetary systems that harbor several terrestrial planets near MMRs inside and one gas-giant exterior to them.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2024-06-08
Abstract: In this work, we investigate the size, thermal inertia, surface roughness and geometric albedo of 10 Vesta family asteroids by using the Advanced Thermophysical Model (ATPM), based on the thermal infrared data acquired by mainly NASA’s Wide-field Infrared Survey Explorer (WISE). Here we show that the average thermal inertia and geometric albedo of the investigated Vesta family members are 42 $ rm J m^{-2} s^{-1/2} K^{-1}$ and 0.314, respectively, where the derived effective diameters are less than 10 km. Moreover, the family members have a relatively low roughness fraction on their surfaces. The similarity in thermal inertia and geometric albedo among the V-type Vesta family member may reveal their close connection in the origin and evolution. As the fragments of the cratering event of Vesta, the family members may have undergone similar evolution process, thereby leading to very close thermal properties. Finally, we estimate their regolith grain sizes with different volume filling factors.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2024-06-08
Abstract: The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade. Benefitting from that, our global understanding of the planet formation processes has been substantially improved. In this review, we first summarize the cutting-edge states of the exoplanet and disk observations. We further present a comprehensive panoptic view of modern core accretion planet formation scenarios, including dust growth and radial drift, planetesimal formation by the streaming instability, core growth by planetesimal accretion and pebble accretion. We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations. Finally, we point out the critical questions and future directions of planet formation studies.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2024-06-08
Abstract: The Standards of Fundamental Astronomy (SOFA) is a service provided by the International Astronomical Union (IAU) that offers algorithms and software for astronomical calculations, which was released in two versions by FORTRAN 77 and ANSI C, respectively. In this work, we implement the python package PyMsOfa for SOFA service by three ways: (1) a python wrapper package based on a foreign function library for Python (ctypes), (2) a python wrapper package with the foreign function interface for Python calling C code (cffi), and (3) a python package directly written in pure python codes from SOFA subroutines. The package PyMsOfa has fully implemented 247 functions of the original SOFA routines. In addition, PyMsOfa is also extensively examined, which is exactly consistent with those test examples given by the original SOFA. This python package can be suitable to not only the astrometric detection of habitable planets of the Closeby Habitable Exoplanet Survey (CHES) mission (Ji et al. 2022), but also for the frontiers themes of black holes and dark matter related to astrometric calculations and other fields. The source codes are available via https://github.com/CHES2023/PyMsOfa.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conicapproximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: With the growing significance of space weather forecasting, multi-layer magnetic and helioseismic telescopes are emerging as a key area of research. However, owing to the diverse operational processes and sophisticated hardware configurations of these devices, there is an urgent need for efficient autonomous observation capabilities. An autonomous Master Control System (MCS) can ensure efficient performance, data consistency, and stability, and the prototype presented here adopts a microservices architecture, breaking down the hardware into multiple subsystems and converting their functions into individual services. A central decision-making system leads the operations, supported by three auxiliary systems and three device control systems. Through inter-subsystem service calls, it achieves rapid imaging and spectroscopic monitoring. To verify system stability and observation efficiency, the system was tested on the Solar Full-disk Multi-layer Magnetograph. Experimental results verify this system can operate automatically for 4 consecutive months, acquire photospheric vector magnetic and Doppler velocity fields within a 15-minute interval, and measure chromospheric longitudinal magnetic and Doppler velocity fields in under 180 s. This ensures consistent and stable solar monitoring and serves as a practical methodological benchmark for the development of similar devices.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The reconstruction of muon energies is crucial for the data analysis of neutrino experiments using large water Cherenkov detectors, but the resolution for muon energy reconstruction using traditional methods is poor. Here, we propose a revised approach to remove noisy optical modules along the track produced by the propagation of muons through water. The number of photons on the optical modules is first corrected by the attenuation properties of light in water. Then the difference in time between the observed optical modules and the expected ones is determined based on the geometry of the triggered optical modules. Finally, the standard of correction is measured by the ratio of photon number before and after correction. Optical modules selection conditions were optimized according to these parameters, with most noisy optical modules successfully removed, improving the resolution of muon energy reconstruction.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The Educational Adaptive-optics Solar Telescope (EAST) at the Shanghai Astronomy Museum has been running routine astronomical observations since 2021. It is a 65-cm-aperture Gregorian solar telescope for scientific education, outreach, and research. The telescope system is designed in an “open” format so that the solar tower architecture can be integrated with it, and visitors can watch the observations live from inside the tower. Equipped with adaptive optics, a high-resolution imaging system, and an integral field unit spectro-imaging system, this telescope can obtain high-resolution solar images in the TiO and Hα bands, and perform spectral image reconstruction using 400 optical fibers at selected wavelengths. It can be used not only in public education and scientific outreach but also in solar physics research.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The primary mirrors of current and future large telescopes always employ a segmented mirror configuration. The small but non-negligible gaps between neighboring segments cause additional diffraction, which restricts the performance of high-contrast coronagraph. To solve this problem, we propose a coronagraph system based on a single liquid crystal spatial light modulator (SLM). This spatial light modulator is used for amplitude apodization, and its feasibility and potential performance are demonstrated using a laboratory setup using the stochastic parallel gradient descent (SPGD) algorithm to control the spatial light modulator, which is based on point spread function (PSF) sensing and evaluation and optimized for maximum contrast in the discovery working area as a merit function. The system delivers a contrast in the order of 10−6, and shows excellent potential to be used in current and future large aperture telescopes, both on the ground and in space.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: Research on adaptive deformable mirror technology for voice coil actuators (VCAs) is an important trend in the development of large ground-based telescopes. A voice coil adaptive deformable mirror contains a large number of actuators, and there are problems with structural coupling and large temperature increases in their internal coils. Additionally, parameters of the traditional proportional integral derivative (PID) control cannot be adjusted in real-time to adapt to system changes. These problems can be addressed by introducing fuzzy control methods. A table lookup method is adopted to replace real-time calculations of the regular fuzzy controller during the control process, and a prototype platform has been established to verify the effectiveness and robustness of this process. Experimental tests compare the control performance of traditional and fuzzy proportional integral derivative (Fuzzy-PID) controllers, showing that, in system step response tests, the fuzzy control system reduces rise time by 20.25%, decreases overshoot by 78.24%, and shortens settling time by 67.59%. In disturbance rejection experiments, fuzzy control achieves a 46.09% reduction in the maximum deviation, indicating stronger robustness. The Fuzzy-PID controller, based on table lookup, outperforms the standard controller significantly, showing excellent potential for enhancing the dynamic performance and disturbance rejection capability of the voice coil motor actuator system.
Subjects: Astronomy >> Astrophysical processes submitted time 2024-06-03
Abstract: The planetary obliquity plays a significant role in determining physical properties of planetary surfaces and climate. As direct detection is constrained due to the present observation accuracy, kinetic theories are helpful to predict the evolution of the planetary obliquity. Here the coupling effect between the eccentric Kozai-Lidov (EKL) effect and the equilibrium tide is extensively investigated, the planetary obliquity performs to follow two kinds of secular evolution paths, based on the conservation of total angular momentum. The equilibrium timescale of the planetary obliquity $t_{ mathrm{eq}}$ varies along with $r_{t}$, which is defined as the initial timescale ratio of the tidal dissipation and secular perturbation. We numerically derive the linear relationship between $t_{ mathrm{eq}}$ and $r_{t}$ with the maximum likelihood method. The spin-axis orientation of S-type terrestrials orbiting M-dwarfs reverses over $90^ circ$ when $r_{t} > 100$, then enter the quasi-equilibrium state between $40^ circ$ and $60^ circ$, while the maximum obliquity can reach $130^ circ$ when $r_{t} > 10^4 $. Numerical simulations show that the maximum obliquity increases with the semi-major axis ratio $a_1$/$a_2$, but is not so sensitive to the eccentricity $e_2$. The likelihood of obliquity flip for S-type terrestrials in general systems with $a_2 < 45$ AU is closely related to $m_1$. The observed potential oblique S-type planets HD 42936 b, GJ 86 Ab and $ tau$ Boot Ab are explored to have a great possibility to be head-down over the secular evolution of spin.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2024-06-02
Abstract: The Closeby Habitable Exoplanet Survey (CHES) employs state-of-the-art, high-precision astrometry and positioning technology at the microarcsecond level in space. Its primary objective is to conduct a thorough survey of approximately 100 FGK-type stars within the Sun’s proximity (within 10 parsecs), with the goal of detecting potentially habitable Earth-like planets or super-Earths. This pioneering mission involves a detailed census of habitable planets, providing intricate information on their numbers, true masses, and three-dimensional orbits. Notably, CHES marks a historic milestone as the inaugural international space exploration mission exclusively dedicated to the study of terrestrial planets within the nearby habitable zone. CHES’s payload features a cutting-edge optical telescope with a 1.2 m aperture, a field of view measuring 0.44°×0.44°, and a focal length of 36 m. The telescope utilizes a coaxial three-mirror TMA optical imaging system. Impressively, CHES is designed with a positioning measurement accuracy of 1 μas, solidifying its status as the most precise space exploration project globally in terms of positioning accuracy. To achieve the detection objectives of CHES, it is essential to refine and further substantiate the scientific goals through comprehensive argumentation. Overcoming three key technological challenges is crucial: advancing optical systems for large field of view, developing high-quality space telescopes with minimal distortion; breaking through measurement technology for stellar separations at the 10–5 pixel level; and achieving high stability in satellite system attitude control and thermal control precision. CHES stands on the threshold of groundbreaking discoveries, with the exciting prospect of revealing 50 Earth-like planets. This announces a significant leap forward in China’s space science exploration technology.
Subjects: Physics >> Nuclear Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-05-29
Abstract: It is hypothesized that, though atomic nuclei are made of nucleons, strongly interacting matter with baryon number from $A simeq 10^{3-9}$ to $ sim 10^{57}$ would be composed of strangeons if Nature favors always the flavor symmetry of quarks. According to that logic, strangeon matter with $A sim 10^{57}$ could manifest in the form of pulsar-like compact stars, and multi-messenger observations with advanced facilities (e.g., China’s FAST) could eventually provide a disproof/proof. It is worth emphasizing that this point of view, based on established “old physics”, may have particular consequences for understanding our material world, for both normal luminous matter and the dark sector.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2024-05-24 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract: In this study, we present a catalog of molecular clumps extracted from 13CO (J = 1 − 0) emission data of the Milky Way Imaging Scroll Painting (MWISP) project. The data covers the inner Milky Way within the longitude range 10° ≤ l ≤ 20° and the latitude strip of . The workflow for the extraction of clumps, namely Facet-SS-3D-Clump, consists of two parts: the identification of clump candidates and their verification. First, Facet-SS-3D-Clump employs FacetClumps to identify clump candidates. Subsequently, high-confidence clumps are obtained by cross-matching with the clumps detected by other algorithms, such as dendrogram. Second, these high-confidence clumps are used as prior knowledge to train a semi-supervised deep clustering approach, SS-3D-Clump, which is applied to verify clump candidates detected by FacetClumps, providing confidence levels for the molecular clumps. Finally, the catalog comprising 18,757 molecular clumps was obtained using Facet-SS-3D-Clump, and the catalog is 90% complete above 37 K km s−1. We observe a significant deviation of the mean Galactic latitude for clumps within ∣b∣ ≤ 2° from the midplane, with . We found that 82.3% of the dust clumps correspond to 13CO clumps by matching with Herschel infrared dust clumps. In the future, Facet-SS-3D-Clump will be applied to detect 13CO clumps in the entire MWISP data.
Subjects: Astronomy >> Astrophysical processes submitted time 2024-05-24 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract: Cassiopeia A (Cas A) is a well-known candidate for studying cosmic-ray acceleration, in which compact features of various scales have attracted much attention. Based on observations by the Very Large Array of Cas A at 6 cm and 21 cm, we measure the spectral index distribution of various scale components using the observation of the 1998 epoch. We decompose its total density image into nine scale components, and map the temperature spectral index distribution of each component, which ranges from −2.48 ± 0.01 to −2.91 ± 0.05. We find that the spectral indices increase from the small scale to large scale components. A damped post-shock magnetic field model with a strength larger than ∼200 μG and a damping length scale less than ∼10% of the remnant radius can account for the spectral index variation naturally.
Subjects: Astronomy >> Astrophysical processes submitted time 2024-05-24 Cooperative journals: 《Research in Astronomy and Astrophysics》
Abstract: Temporary capture efficiency is studied in the framework of the circular restricted three-body problem in two steps. First, a non-uniform distribution of test particles around the secondary’s orbit is obtained by fully accounting the secondary’s gravitational influence. Second, the capture efficiency is computed based on the non-uniform distribution. Several factors influencing the result are discussed. By studying the capture efficiency in the circular restricted three-body problem of different mass ratios, a power-law relation between the capture efficiency (p) and the mass ratio (μ) is established, which is given by p ≈ 0.27 × μ0.53, within the range of 3.0035 ×10−6 ≤ μ ≤ 3.0034 × 10−5. Taking the Sun–Earth system as an example, the influence from the orbit eccentricity of the secondary on the non-uniform distribution and the capture efficiency is studied. Our studies find that the secondary’s orbit eccentricity has a negative influence on the capture efficiency.