Observatory Research Articles

THE POEM “SONG ABOUT THE REFRACTOR”: SCIENTIFIC HUMOR IN THE CONTEXT OF RELATIONS BETWEEN RUSSIAN AND GERMAN SCIENTISTS AT THE TURN OF THE 19TH AND 20TH CENTURIES

The history of science is intended to study not only the history of discoveries, hypotheses and methodology, but also human connections, which sometimes influence the formation and development of scientific knowledge no less than articles and books. Ephemerides of various kinds are particularly difficult to observe and study: topical hints understood only in a narrow circle, various statements on a subject that may be forgotten after the passage of time, a way of joking that has long since lost its relevance - all that is woven into the fabric of life, including scientific one, and without which it is impossible to imagine people who did science. At the center of the article is a poetic text found in the archive of the remarkable Russian astronomer V.K. Tserasky, who headed the Astronomical Observatory of Moscow University at the turn of the 19th and 20th centuries and put a lot of effort into its construction. The humorous work “Song about the Refractor” (1898) by the Berlin student Benno Messow is one of such samples of humor, which can shed light on the nature of scientific contacts between scholars from different countries. The poem is a paraphrase of Friedrich Schiller’s famous “Song of the Bell”, deeply rooted in the tradition of German poetry. Meanwhile, the parodic “song” was presented to V.K. Tserasky, who, according to the presenter’s thought, was able to appreciate the subtlety of the joke. The construction of a refractor in the Moscow observatory seemed an excellent occasion to reuse the text dedicated to the completion of the same device in the Potsdam Astrophysical Observatory. This work is a testimony both to the scientists’ penchant for humor and to the versatile scientific and friendly ties between scholars and engineers of Russia and Germany at the turn of the nineteenth and twentieth centuries. The article examines Messow’s poem, some details of his biography and the alleged circumstances of the song’s transfer to V.K. Tserasky.

The Astrological Schemes Behind bīt niṣirtu and KI in the Babylonian Horoscopes

Abstract The Babylonian horoscopes, edited by Rochberg in 1998, contain sets of astronomical and astrological data on dates of, or close to, individuals’ births. Each element of these short and concise texts reflects the astral divinatory practices and astronomical observation developed over the first millennium BC, as well as the latest innovations, including the zodiac as coordinate system and the occurrence of new astrological schemes partly based on it, which had previously remained obscure. In this paper, I present a new interpretation of the astrological terminology and the schemes that underly some of the data in the Babylonian horoscopes.

M3DIS - A grid of 3D radiation-hydrodynamics stellar atmosphere models for stellar surveys. I. Procedure, validation, and the Sun

Large-scale stellar surveys, such as SDSS-V, 4MOST, WEAVE, and PLATO, require accurate atmospheric models and synthetic spectra of stars for accurate analyses of fundamental stellar parameters and chemical abundances. The primary goal of our work is to develop a new approach to solve radiation-hydrodynamics (RHD) and generate model stellar spectra in a self-consistent and highly efficient framework. We build upon the Copenhagen legacy RHD code, the MULTI3D non-local thermodynamic equilibrium (NLTE) code, and the DISPATCH high-performance framework. The new approach allows us to calculate 3D RHD models of stellar atmospheres on timescales of a few thousand CPU hours and to perform subsequent spectrum synthesis in local thermodynamic equilibrium (LTE) or NLTE for the desired physical conditions within the parameter space of FGK-type stars. We compare the 3D RHD solar model with other available models and validate its performance against solar observations, including the centre-to-limb variation of intensities and key solar diagnostic lines of H and Fe. We show that the performance of the new code allows to overcome the main bottleneck in 3D NLTE spectroscopy and enables calculations of multi-dimensional grids of synthetic stellar observables for comparison with modern astronomical observations.

Sustainable astronomy: A comparative life cycle assessment of off-grid hybrid energy systems to supply large telescopes

PurposeSupplying off-grid facilities such as astronomical observatories with renewable energy–based systems (RES) instead of diesel generators can considerably reduce their environmental impact. However, RES require oversized capacities to counter intermittency and comply with reliability requirements, hence shifting the environmental impact from operation to construction phase. We assess whether 100% RES scenarios are favorable from an environmental point of view and discuss the trade-offs in systems with backup fossil generators versus 100% renewable ones.MethodsIn this comparative life cycle assessment (LCA), we study various RES supply systems to power a new telescope in the Atacama Desert, Chile. We compare six setups, including 100% RES scenarios, namely, photovoltaics (PV) with batteries and hydrogen energy storage; high-renewable scenarios, with fossil fuel power generation next to RES and storage; and a system combining PV with diesel generation. We base system sizing on a techno-economical optimization for the start of operation in 2030. Foreground data stem from life cycle inventories of RES components since 2015 and 2030 electricity mix assumptions of production countries. We assess environmental impact in the categories climate change, mineral resource depletion, and water use.Results and discussionWe find that 100% RES and high-renewable scenarios result in emissions of 0.077–0.115 kg CO2e/kWh supplied, compared to 0.917 kg CO2e/kWh in the reference case with solely diesel generation. One hundred percent RES scenarios have a lower CO2e impact than high-renewable scenarios. However, the latter lower the mineral resource depletion and water use by about 27% compared to 100% RES scenarios. Applying hybrid energy storage systems increases the water use impact while reducing the mineral resource depletion.ConclusionsNone of the six energy systems we compared was clearly the best in all environmental impacts considered. Trade-offs must be taken when choosing an energy system to supply the prospective off-grid telescope in Chile. We find high-renewable systems with some fossil generation as the better option regarding power reliability, mineral resource depletion, and water use, while inducing slightly higher greenhouse gas emissions than the 100% RES scenarios. As remote research facilities and off-grid settlements today are mainly supplied by fossil fuels, we expect to motivate more multifaceted decisions for implementing larger shares of RES for these areas. To advance the LCA community in the field of energy systems, we should strive to incorporate temporal and regional realities into our life cycle inventories. To ease the path for upcoming studies, we publish this work’s inventories as detailed activity level datasets.

Performance of a High-Speed Pyroelectric Receiver as Cryogen-Free Detector for Terahertz Absorption Spectroscopy Measurements

The application of terahertz (THz) radiation in scientific research as well as in applied and commercial technology has expanded rapidly in recent years. One example is the progress in high-resolution THz spectroscopy based on quantum cascade lasers, which has enabled new observations in astronomy, atmospheric research, and plasma diagnostics. However, the lack of easy-to-use and miniaturised detectors has hampered the development of compact THz spectroscopy systems out of the laboratory environment. In this paper, we introduce a new high-speed pyroelectric receiver as a cryogen-free detector for THz absorption spectroscopy. Its performance is characterised by absorption spectroscopy measurements on a reference gas cell (RGC) with ammonia using a tunable THz quantum cascade laser at approximately 4.75 THz as the light source. It is shown that the receiver can record spectra up to 281 Hz without any artefacts to the observed spectral absorption profile, and the results reproduce the known pressure of ammonia in the RGC. This demonstrates that the pyroelectric receiver can be reliably used as an alternative to helium-cooled bolometers for absorption spectroscopy measurements in the THz range, with its main advantages being the high bandwidth, compactness, relatively low cost, and room-temperature operation. Its simplicity and high sensitivity make this receiver a key component for compact THz spectroscopy systems.

Multicolour photometry of LEO mega-constellations Starlink and OneWeb

ABSTRACT The development of low earth orbit (LEO) mega-constellation fundamentally threatens ground-based optical astronomical observations. To study the photometric properties of the LEO mega-constellations, we used the Xinglong 50 cm telescope to conduct a large-sample, high-precision, and multicolour target-tracking photometry of two typical LEO mega-constellations: Starlink and OneWeb. Over a three-month observation period starting on 2022 January 1, we collected 1447 light curves of 404 satellites in four typical versions: Starlink v1.0, DarkSat, VisorSat, Starlink v1.5, and OneWeb. According to data statistics, Starlink v1.0 has the smallest median magnitude at clear and Sloan Digital Sky Survey gri band, and OneWeb is the dimmest bus. The brightness of Starlink v1.5 is slightly brighter than VisorSat. We construct a detailed photometric model with solar phase angle variations by calculating the illumination-visibility geometry based on the orbital parameters. Our data analysis shows that the solar phase angle is the significant characteristic which influencing Starlink satellites’ brightness, but it is not sensitive to OneWeb satellites. VisorSat and Starlink v1.5 versions, which are equipped with deployable visors, have significantly reduced scattered light compared to the previous Starlink v1.0 version. The multiband LOWESS and colour index are analysed in characterizing the energy and colour features of LEO mega-constellation satellites. This work found that the proportion of scattered sunlight mitigation achieved with VisorSat and Starlink v1.5 was 55.1 and 40.4 per cent, respectively. The colour index of different buses shows an evident clustering feature. Our observation and analysis could provide valuable quantitative data and photometric models, which can contribute to assessing the impact of LEO mega-constellations on astronomical observations.

Optical spectroscopic and photometric classification of the X-ray transient EP240309a (EP J115415.8−501810) as an intermediate polar

ABSTRACT We report on optical follow-up observations of an X-ray source initially detected by the Einstein Probe mission. Our investigations categorize the source as an intermediate polar, a class of magnetic cataclysmic variables, exhibiting an orbital period of 3.7614(4) h and a white dwarf spin period of 3.97 min. The orbital period was identified through TESS observations, while our high-speed photometric data, obtained using the 1.9m and Lesedi 1.0m telescopes at the South African Astronomical Observatory, revealed both the spin and beat periods. Additionally, we present orbitally phase-resolved spectroscopic observations using the 1.9m telescope, specifically centred on the H β emission line, which reveal two emission components that exhibit Doppler variations throughout the orbital cycle.

Integrated life cycle assessment in off-grid energy system design—Uncovering low hanging fruit for climate mitigation

We perform an ex-ante life cycle assessment, integrating cradle-to-gate greenhouse gas emissions into an off-grid energy system model. By applying a multi-objective optimization, minimizing both costs and carbon dioxide equivalent (CO2e) emissions, we find the Pareto boundary between these two goals. As a case study, we chose the power supply to an astronomical observatory in Chile, using mostly solar power and energy storage in batteries and hydrogen. We compare the ex-ante study to a prior ex-post life cycle assessment, and furthermore dive into sensitivities of our model regarding component lifetimes and costs. We find (i) low-hanging fruit in lowering emissions with small cost increases, (ii) ex-ante life cycle assessments’ possibility to find less CO2e intensive power systems compared to ex-post conducted studies, (iii) a pronounced sensitivity of the optimization model on assumed lifetimes of energy storage components. This study shows the importance of including life cycle CO2e emissions into the optimization objective of energy system models. This method uncovers the environmental and economic trade-offs associated with high shares of renewable energies in off-grid energy systems.

Radiation tolerance test and performance verification of pnCCD at high temperatures for future satellite mission HiZ-GUNDAM

A wide-field X-ray survey in the soft X-ray band is crucial for future satellite missions in the astronomical observations. HiZ-GUNDAM, currently under development, is a proposed satellite designed to observe soft X-ray transients including gamma-ray bursts. This satellite employs wide-field X-ray monitors consisting of lobster-eye optics and focal-plane pixel sensors in the soft X-ray band of 0.4–4 keV. A pnCCD is a candidate for focal-plane Si pixel detectors, featuring a back-illuminated X-ray CCD, large pixel size (70–100 µm), and a large active image area of approximately 55 × 55 mm2 for the flight model. Here, we investigated the basic characteristics and performance of the small-size pnCCD with 128 × 256 pixels, a pixel size of 75 µm, and a detector thickness of 450 µm. High-energy cosmic rays such as protons can degrade the performance of pnCCDs by increasing dark current and charge transfer inefficiency due to ionizing and displacement damage. These factors may affect soft X-ray observations, potentially causing the degradation of lower-detectable energy thresholds and an increase in the number of hot pixels. Therefore, we conducted a radiation tolerance test at room temperature using a proton beam. After irradiating the pnCCD with 10-MeV protons equivalent to three years of nominal operation for HiZ-GUNDAM, we found that the operation temperatures of the pnCCD should be lower than -35 °C. This requirement will be incorporated into the design of the mission operation system.

Digitization of Astronomical Photographic Plates of China and Astrometric Measurement of Single-exposure Plates

From the mid-19th century to the end of the 20th century, photographic plates served as the primary detectors for astronomical observations. Astronomical photographic observations in China began in 1901, and over a century, a total of approximately 30,000 astronomical photographic plates were captured. These historical plates play an irreplaceable role in conducting long-term, time-domain astronomical research. To preserve and explore these valuable original astronomical observational data, Shanghai Astronomical Observatory has organized the transportation of plates, taken during nighttime observations from various stations across the country, to the Sheshan Plate Archive for centralized preservation. For the first time, plate information statistics were calculated. On this basis, the plates were cleaned and digitally scanned, and finally digitized images were acquired for 29,314 plates. In this study, using Gaia DR2 as the reference star catalog, astrometric processing was carried out successfully on 15,696 single-exposure plates, including object extraction, stellar identification, and plate model computation. As a result, for long focal length telescopes, such as the 40 cm double-tube refractor telescope, the 1.56 m reflector telescope at Shanghai Astronomical Observatory, and the 1m reflecting telescope at Yunnan Astronomical Observatory, the astrometric accuracy obtained for their plates is approximately 0.″1–0.″3. The distribution of astrometric accuracy for medium and short focal length telescopes ranges from 0.″3 to 1.″0. The relevant data of this batch of plates, including digitized images and a stellar catalog of the plates, are archived and released by the National Astronomical Data Center. Users can access and download plate data based on keywords such as station, telescope, observation year, and observed celestial coordinates.

DarkGEO: a large-scale laser-interferometric axion detector

Axions and axion-like particles (ALPs) are leading candidates for dark matter. They are well motivated in many extensions of the standard model and supported by astronomical observations. We propose an iterative transformation of the existing facilities of the gravitational-wave detector and technology testbed GEO600, located near Ruthe in Germany, into a kilometre-scale upgrade of the laser-interferometric axion detector LIDA. The final DarkGEO detector could search for coincident signatures of axions and ALPs and significantly surpass the current constraints of both direct searches and astrophysical observations in the measurement band from 10−16 to 10−8eV. We discuss design parameters and sensitivities for the configurations of the different iteration steps as well as technical challenges known from the first LIDA results. The proposed DarkGEO detector will be well suited to probe the mass-coupling parameter space associated with predictions from theoretical models, like grand-unified theories, as well as from astrophysical evidence, like the cosmic infrared background.

Machine learning bias correction and downscaling of urban heatwave temperature predictions from kilometre to hectometre scale

AbstractThe urban heat island (UHI) effect exacerbates near‐surface air temperature (T) extremes in cities, with negative impacts for human health, building energy consumption and infrastructure. Using conventional weather models, it is both difficult and computationally expensive to simulate the complex processes controlling neighbourhood‐scale variation of T. We use machine learning (ML) to bias correct and downscale T predictions made by the Met Office operational regional forecast model (UKV) to 100 m horizontal grid length over London, UK. A set of ML models (random forest, XGBoost, multiplayer perceptron) are trained using citizen weather station observations and UKV variables from eight heatwaves, along with high‐resolution land cover data. The ML models improve the T mean absolute error (MAE) by up to 0.12°C (11%) relative to the UKV. They also improve the UHI diurnal and spatial representation, reducing the UHI profile MAE from 0.64°C (UKV) to 0.15°C. A multiple linear regression performs almost as well as the ML models in terms of T MAE, but cannot match the UHI bias correction performance of the ML models, only reducing the UHI profile MAE to 0.49°C. UKV latent heat flux is found to be the most important predictor of T bias. It is demonstrated that including more heatwaves and observation sites in training would reduce overfitting and improve ML model performance.

The Robotic MAAO 0.7 m Telescope System: Performance and Standard Photometric System

We introduce a 0.7 m telescope system at the Miryang Arirang Astronomical Observatory (MAAO), a public observatory in Miryang, Korea. System integration and a scheduling program enable the 0.7 m telescope system to operate completely robotically during nighttime, eliminating the need for human intervention. Using the 0.7 m telescope system, we obtain atmospheric extinction coefficients and the zero-point magnitudes by observing standard stars. As a result, we find that atmospheric extinctions are moderate but they can sometimes increase depending on the weather conditions. The measured 5σ limiting magnitudes reach down to BVRI = 19.4–19.6 AB mag for a point source with a total integrated time of 10 minutes under clear weather conditions, demonstrating comparable performance with other observational facilities operating under similar specifications and sky conditions. We expect that the newly established MAAO 0.7 m telescope system will contribute significantly to the observational studies of astronomy. Particularly, with its capability for robotic observations, this system, although its primary duty is for public viewing, can be extensively used for the time-series observation of transients.

ЗАКОНОМЕРНОСТИ ИЗМЕНЕНИЯ КОНЦЕНТРАЦИЙ CO2 И CH4 ПО РЕЗУЛЬТАТАМ ИЗМЕРЕНИЙ В ПРИЗЕМНОМ СЛОЕ АТМОСФЕРЫ ГОРОДСКОЙ И ЗАГОРОДНОЙ ТЕРРИТОРИИ В 2021-2022 ГОДАХ

The patterns and factors of changes in CO2 and CH4 concentrations in the surface atmosphere of an urbanized and suburban environment were analyzed based on the results of the synchronous measurements in Yekaterinburg and the Kourovka Astronomical Observatory (KAO) in September 2021–August 2022. On average, the maximum levels of CO2 in Yekaterinburg (443.2 ppm) were shown to be higher than in KAO (432.4 ppm) and were reached in January. The minima, on the contrary, were lower in the city than in the suburban area (405.4 ppm in July in Yekaterinburg against 412.7 ppm in September in KAO). Enhanced CO2 levels in the warm season in KAO were caused by very high nighttime concentrations (up to 500 ppm), which was not observed in the surface urban atmosphere. For CH4, the seasonal dynamics in the city and in KAO was similar: the maximum levels were reached in January (2.154 and 2.076 ppm), and the minima were registered in June (1.998 and 1.971 ppm). The mutual influence of the territories under consideration was assessed to be moderate. The results of the study can be used to develop a technology for assessing the carbon balances on a regional scale, which is the main task of the Carbon Supersites program in the Urals.

Gravitational lensing by a stable rotating regular black hole

Recent observational data from the Event Horizon Telescope (EHT) collaboration provide convincing realistic evidence for the existence of black hole rotation. From a phenomenological perspective, a recently proposed stable rotating regular (SRR) black hole circumvents the theoretical flaws of the Kerr solution. For the purpose of obtaining observational signatures of this black hole, we study its gravitational lensing effect. In the strong deflection limit, we calculate the deflection angle of light on the equatorial plane, the radius of the photon sphere, and other observables. The observables include the relativistic image position, separation, magnification, and time delays between different images. Then, by modeling M87* and Sgr A* as the SRR black hole, we compute their observables and evaluate the deviation of the observables from the Kerr case. In the weak deflection limit, we calculate the light deflection angle on the equatorial plane of M87* and Sgr A* via the Gauss-Bonnet theorem (GBT). With the growth of deviation parameter e, the gravitational lensing effect in the weak deflection limit intensifies monotonically, and the gravitational lensing effect in the strong deflection limit changes dramatically only at high spins. Our research may contribute to distinguish between SRR black holes from Kerr black holes under higher-precision astronomical observations.

Inquiry-based astronomy in West Java secondary schools

This study investigates the presence and utilisation of inquiry-based activities in astronomy education within secondary science and physics classrooms. Employing document analysis, surveys, classroom observations, and interviews, the study comprehensively assesses the nature of inquiry activities, teachers’ experiences, integration of astronomy into curriculum, resources availability and science teachers’ perceived proficiency in astronomical observation skills. Findings from 50 secondary science and senior high physics teachers reveal coverage of the Solar System and Earth–Moon–Sun motion in secondary science, and integration of astronomy concepts like universal gravitation and Kepler’s laws into physics classrooms. However, inquiry-based astronomy teaching is limited, with only 10% of educators feeling proficient in telescope use and low adoption of virtual laboratories and simulations. The study underscores the necessity for adaptive inquiry-based activities in astronomy education to enhance science and physics classrooms, proposing direct and indirect celestial object observation, virtual inquiries, and hands-on simulations to bridge skill gaps and resource utilisation shortcomings, thus enriching astronomy education at the secondary level.

Real-time Abnormal Detection of GWAC Light Curve based on Wavelet Transform Combined with GRU-Attention

Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutionary history of celestial bodies. The Ground-based Wide Angle Cameras telescope, on which this paper is based, has observed more than 10 million light curves, and the detection of anomalies in the light curves can be used to rapidly detect transient rare phenomena such as microgravity lensing events from the massive data. However, the traditional statistically based anomaly detection methods cannot realize the fast processing of massive data. In this paper, we propose a Discrete Wavelet (DW)-Gate Recurrent Unit-Attention (GRU-Attention) light curve warning model. Wavelet transform has good effect on data noise reduction processing and feature extraction, which can provide richer and more stable input features for a neural network, and the neural network can provide more flexible and powerful output model for wavelet transform. Comparison experiments show an average improvement of 61% compared to the previous pure long-short-term memory unit (LSTM) model, and an average improvement of 53.5% compared to the previous GRU model. The efficiency and accuracy of anomaly detection in previous paper work are not good enough, the method proposed in this paper possesses higher efficiency and accuracy, which incorporates the Attention mechanism to find out the key parts of the light curve that determine the anomalies. These parts are assigned higher weights, and in the actual anomaly detection, the star is detected with 83.35% anomalies on average, and the DW-GRU-Attention model is compared with the DW-LSTM model, and the detection result f1 is improved by 5.75% on average, while having less training time, thus providing valuable information and guidance for astronomical observation and research.

The Experiences of High School Students about Astronomical Observation Activities Seen through the Movement of Deleuzian “Becoming”

The Experiences of High School Students about Astronomical Observation Activities Seen through the Movement of Deleuzian “Becoming”

Bridging relativistic jets from black hole scales to long-term electromagnetic radiation distances: A moving-mesh general relativistic hydrodynamics code with the HLLC Riemann solver

Relativistic jets accompany the collapse of massive stars, the merger of compact objects, or the accretion of gas in active galactic nuclei. They carry information about the central engine and generate electromagnetic radiation. No self-consistent simulations have been able to follow these jets from their birth at the black hole scale to the Newtonian dissipation phase, making the inference of central engine property through astronomical observations undetermined. We present the general relativistic moving-mesh framework to achieve the continuity of jet simulations throughout space and time. We implement the general relativistic extension for the moving-mesh relativistic hydrodynamic code, , and develop a tetrad formulation to utilize the Harten-Lax-van Leer Contact Riemann solver in the general relativistic moving-mesh code. The new framework is able to trace the radial movement of relativistic jets from central regions where strong gravity holds all the way to distances of jet dissipation. Published by the American Physical Society 2024

Analysis of Urban Heat Island Effect in Wuhan Urban Area Based on Prediction of Urban Underlying Surface Coverage Type Change

The rapid development of urbanization makes the phenomenon of urban heat islands even more serious. Predicting the impact of land cover change on urban heat island has become one of the research hotspots. Taking Wuhan, China, as an example, this study simulated the land type change in 2020 through the Cellular Automata-Markov-Chain (CA-Markov) model. The urban heat island in 2020 was simulated and analyzed in conjunction with the Weather Research & Forecasting Model (WRF), and the simulation results of wind velocity and temperature were confirmed using weather station observation data. Based on this, the land cover and urban heat island of Wuhan in 2030 were predicted. The temperature was found to be well-fit by CA-Markov simulated land use data, with an average inaccuracy of about 2.5°C for weather stations. Wind speed had a poor fitting effect; the average error was roughly 2 m/s. The built-up area was the center of the high temperature area both before and after the prediction, the water was the low temperature area, and the peak heat island happened at night. According to the forecast results, there will be more built-up land in 2030, and there will be a greater intensity of heat islands than in 2020.