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In this reply, the aim of the authors is to correct the calculation errors on solar depression angle and azimuth angle as recognized by Dr. Dalin in his critical review. However, these updated and corrected calculations do not affect the possibility for Antonio Colla of having observed the Noctilucent Cloud (NLC) plausible both in the direction and for the duration he described in his observations. In this reply, the authors offer two different interpretations in this regard. [ABSTRACT FROM AUTHOR]

One of the fundamental goals of modern astrophysics is to estimate the physical parameters of galaxies. We present a hierarchical Bayesian model to compute age maps from images in the H α line (taken with Taurus tunable filter, TTF), ultraviolet band (GALEX far UV, FUV), and infrared bands (Spitzer 24, 70, and 160 |$\mu$| m). We present the burst ages for young stellar populations in a sample of nearby and nearly face-on galaxies. The H α to FUV flux ratio is a good relative indicator of the very recent star formation history (SFH). As a nascent star-forming region evolves, the H α line emission declines earlier than the UV continuum, leading to a decrease in the H α/FUV ratio. Using star-forming galaxy models, sampled with a probabilistic formalism, and allowing for a variable fraction of ionizing photons in the clusters, we obtain the corresponding theoretical ratio H α/FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. We take into account the mean uncertainties and the interrelationships between parameters when computing H α/FUV. We propose a Bayesian hierarchical model where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF) from the observed data (the observed flux ratios H α/FUV). The joint distribution of the parameters is described through independent and identically distributed (i.i.d.) random variables generated through MCMC (Markov Chain Monte Carlo) techniques. [ABSTRACT FROM AUTHOR]

Abstract: This is the first of a series of four papers, the goal of which is to identify the overcontact eclipsing binary star systems for which a solid case can be made for mass exchange. To reach this goal, it is necessary first to identify those systems for which there is a strong case for period change. We have identified 60 candidate systems; in the present paper and in two succeeding papers we will discuss the individual cases. For each system, we will present a detailed discussion and evaluation concerning the observational and interpretive material presented in the literature. An eclipse timing diagram (or diagrams), commonly referred to as an “O–C diagram”, using the latest available data will accompany each discussion. In paper 3, we will also present a table of marginal and rejected cases. In paper 4, we will present a discussion of the mechanisms that can effect period change and which of the systems presented can be reliably concluded to exhibit mass exchange. [Copyright &y& Elsevier]

The 'Redman K stars' project, described more particularly in the paper immediately following this one, involved the repeated measurement on a quasi-annual basis of the radial velocities of a group of 86 seventh-magnitude late-type stars over an interval of 45 years. Certain of the stars proved to vary in velocity and were then transferred to a different observing programme, in which they were measured more frequently with a view to determining their orbits. Orbits have already been published for 18 of the stars. Presented here (and summarized in Table 9) are the results on six more; all are single-lined. One of them (HD 191046, a star which has a literature coverage about ten times as rich as that of any of the others, probably on account of its high space velocity which includes a γ-velocity of nearly −100 km s) has a good orbit with a period of about 8000 days (22 years). Five others (HD 3345, 15728, 20509, 188058 and 191084) have orbits that are perfectly secure in principle, but their periods range between 40 and perhaps 70 years, and (particularly in some cases) their radial velocities have not been observed well enough for long enough to establish either the periods or the orbits very accurately. One star, HD 9354, has exhibited a monotonic variation of velocity throughout the duration of the observing programme; it is possible to draw a Keplerian velocity curve that does justice to the measurements, but it cannot be expected to have much predictive power. [ABSTRACT FROM AUTHOR]

Scientific results strongly rely on previous studies, experiments, and observations. A huge quantity of data is produced by astronomers and needs to be available to the whole community. To support astronomers in their daily research work, the Centre de Donn´ ees astronomiques de Strasbourg (Strasbourg astronomical data center -- CDS) collects, verifies, homogenizes, and organizes information -- in particular, those published in academic journals -- in the most appropriate and comprehensible way. This CDS goal can reach the highest level of quality only through a close collaboration with journals, authors, and referees. This paper presents the succession of processes leading published data to the CDS databases, focusing on the strategy that maintains a high level of quality. Authors and referees are strongly encouraged to actively contribute to this endeavor. A few examples of how CDS databases are used through CDS services are also presented. [ABSTRACT FROM AUTHOR]

In the present critical review, my aim is to address serious calculation mistakes made by the authors. I do not want to review their interpretation of a given observation on 18 June 1840 made by Antonio Colla, who was a professor of Astronomy and Meteorology at the University of Parma. There is no sense interpreting Colla's observation since the basic astronomical calculations have been made incorrectly by the authors Chiara Bertolin and Fernando Domínguez-Castro. Summarizing, in theory and practice, astronomer Antonio Colla could not have observed noctilucent clouds (NLC) at Parma on 18 June 1840. That is why the conclusions of the present paper are not valid. [ABSTRACT FROM AUTHOR]

The 'Redman K stars' are a group of 80-odd seventh-magnitude late-type stars, nearly all giants, distributed along the Galactic equator between approximate longitudes 50° and 150° (roughly Sagitta to Cassiopeia). Their radial velocities have been measured systematically once per season in 30 of the 45 seasons from 1966 to 2010/11. At least 26 of them (30%) have proved to vary in velocity. Orbits have been derived for all but one of the 26, many of them having longer periods than have normally been associated with spectroscopic binaries; several are comparable with, or longer than, the present duration of the observing campaign. Also reported here are radial-velocity measurements made casually of stars seen in the fields of some of the Redman stars. Two of the companions have proved to vary in velocity on long time-scales, and (somewhat preliminary) orbits are given for them. [ABSTRACT FROM AUTHOR]

We assessed the scientific productivity of XMM- Newton by examining XMM- Newton publications and data usage statistics. We analyse 3272 refereed papers, published until the end of 2012, that directly use XMM- Newton data. The SAO/NASA Astrophysics Data System (ADS) was used to provide additional information on each paper including the number of citations. For each paper, the XMM- Newton observation identifiers and instruments used to provide the scientific results were determined. The identifiers were used to access the XMM-Newton Science Archive (XSA) to provide detailed information on the observations themselves and on the original proposals. The information obtained from these sources was then combined to allow the scientific productivity of the mission to be assessed. Since around three years after the launch of XMM- Newton there have been around 300 refereed papers per year that directly use XMM- Newton data. After more than 13 years in operation, this rate shows no evidence that it is decreasing. Since 2002, around 100 scientists per year become lead authors for the first time on a refereed paper which directly uses XMM- Newton data. Each refereed XMM- Newton paper receives around four citations per year in the first few years with a long-term citation rate of three citations per year, more than five years after publication. About half of the articles citing XMM- Newton articles are not primarily X-ray observational papers. The distribution of elapsed time between observations taken under the Guest Observer programme and first article peaks at 2 years with a possible second peak at 3.25 years. Observations taken under the Target of Opportunity programme are published significantly faster, after one year on average. The fraction of science time taken until the end of 2009 that has been used in at least one article is ∼90%. Most observations were used more than once, yielding on average a factor of two in usage on available observing time per year. About 20 % of all slew observations have been used in publications. The scientific productivity of XMM- Newton measured by the publication rate, number of new authors and citation rate, remains extremely high with no evidence that it is decreasing after more than 13 years of operations. [ABSTRACT FROM AUTHOR]

Aims. As part of our observational projects at the La Silla Danish 1.54-meter telescope, we aim to measure the precise times of minimum light for eccentric eclipsing binaries in the Large Magellanic Cloud, needed for accurate determination of apsidal motion. Many new times of minima were derived from the photometric databases OGLE and MACHO. Several new minima were also observed. Five early-type and eccentric-orbit eclipsing binaries: HV 982 (P = 5.d 34, e = 0.15), HV 2274 (5.d 73, 0.17), MACHO 78.6097.13 (3.d 11, 0.05), MACHO 81.8881.47 (3.d 88, 0.22), and MACHO 79.5377.76 (2.d 64, 0.06) were studied. Methods. The O-C diagrams of the systems were analysed using all reliable timings found in the literature, and new or improved elements of apsidal motion were obtained. Light and radial velocity curves of MACHO 81.8881.47 and MACHO 79.5377.76 were analysed using the program PHOEBE. Results. We derived for the first time or significantly improved the relatively short periods of apsidal motion of 211 (12), 127 (8), 48 (13), 103 (20), and 42 (19) years, respectively. The internal structure constants, log k2, were found to be -2.37, -2.47, -2.17, -2.02, and -1.86 respectively, under the assumption that the component stars rotate pseudosynchronously. The relativistic effects are weak, up to 6% of the total apsidal motion rate. The masses for MACHO 81.8881.47 resulted in 5.51 (0.21) and 5.40 (0.19) M☉, while for MACHO 79.5377.76 the masses are 11.26 (0.35) and 11.27 (0.35) M☉, respectively. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the effect of synoptic-scale forcing on the stratospheric sudden warnings (SSWs) in 2006 in the U.S. The researchers used the meteorological fields from Goddard Earth Observing System (GEOS)-4 analyses in determining such effects. The study found out that stratospheric polar displaced off the pole due to earlier minor warming events. The researchers also suggest that there is a need for further investigation to determine the kind of fraction of major SSWs are initiated.

The first aim of this corrigendum is to point out and correct calculation errors on solar depression angle and azimuth angle in Bertolin and Domínguez-Castro (2020a, 2020b). The second aim is to recognize that these calculations are correct in Dalin (2020). The third aim is to analyze the chances of Antonio Colla to observe the noctilucent cloud (NLC) taking into account the correct calculations of the twilight sky arc determining the illuminated area of an NLC and the uncertainties in the Colla's observation report. [ABSTRACT FROM AUTHOR]

Of 4000 papers published in astronomy and in physics in the past 40 years, 40.3%, and 23.4%, respectively, have not been cited (referenced). However, if we limit this to the final research papers (excluding announcements, book reviews, proposals for funding, and observing time, obituaries, etc.), the fractions are 1.4% and 1.5%, respectively. So virtually all the papers in these two sciences are useful. These data also tell us that the productivities of astronomers peak at age 40.4 years. and that 43.0% were published after the age of 50 years. For physicists, the peak occurs at 36.6 years. and only 33.7% were published after the age of 50 years. Therefore physicists peak about four years earlier than astronomers and they produce 9% fewer citations after the age of 50 years. [ABSTRACT FROM AUTHOR]

This paper presents a mission concept designed for satellite-to-cell connectivity through a fractionated CubeSat approach, aiming to fulfill the objectives set by the BlueWalker-3 specifications. The envisioned system consists of 41 CubeSats, each adopting a 16U form factor, to provide dedicated coverage across specified sub-regions, as a reasonable solution. The pre-Phase-A design capitalizes on commercially available components with proven flight heritage, ensuring reliability and cost-efficiency. A genetic algorithm (GA)-based method has been introduced to tackle the complex challenge of designing a large antenna's folding pattern, with an analysis on how this design influences the overall system cost. The study conducts an in-depth analysis of system architecture and operational scenarios. Employing Monte-Carlo simulations, it assesses the Life Cycle Cost (LCC) and the system's resilience to failures, comparing it with similar configurations differing in CubeSat size and number. The results demonstrate that a fractionated approach significantly enhances the mission's scalability and robustness, providing substantial operational flexibility. The comparison highlights a cost-effective configuration within fractionated systems, emphasizing the proposed system's potential advantages. Furthermore, the paper addresses the environmental implications of deploying a fractionated spacecraft constellation, especially concerning astronomical studies. It underscores the CubeSats' minimized brightness and their reduced potential to interfere with telescopic observations, positioning the system as a more compatible option with nighttime sky studies. This consideration is particularly pertinent amidst increasing concerns over the impact of satellite constellations on astronomical research and night sky quality. • Introduction of a novel mission concept employing fractionated spacecraft for satellite-to-cell connectivity, showcasing an innovative design utilizing 41 CubeSats. • Comparative analysis demonstrating the proposed system's performance and cost advantages over the BlueWalker-3 mission, with findings supported by Monte-Carlo simulations. • Detailed discussion on the use of commercially available off-the-shelf components, highlighting the system's feasibility and reliability. • Exploration of the fractionated system's scalability and robustness, revealing potential for enhanced mission flexibility and economic efficiency. • Addressing the impact on astronomical observations, presenting a significant reduction in brightness and interference, enhancing compatibility with observational studies. [ABSTRACT FROM AUTHOR]

The Moon is a geological history book, preserving information about the history of the Solar System, including the formation and early evolution of the terrestrial planets and their bombardment histories, as well as providing insight into other fundamental Solar System processes. These topics form the basis for science "of the Moon", but the lunar surface is also a platform for science "on the Moon" and "from the Moon"—including astronomical observations, fundamental physics, and life science investigations. Recently, the Moon has become a destination for technology research and development—in particular for developing in situ resources, human exploration, and habitation, and for its potential use as a waypoint for the human exploration of Mars. This paper, based on recommendations originally proposed in a White Paper for ESA's SciSpacE strategy, outlines key lunar science questions that may be addressed by future space exploration missions and makes recommendations for the next decades. [ABSTRACT FROM AUTHOR]

Light pollution has a detrimental effect on astronomy. Artificial light emitted from outdoor lighting increases the brightness of the night sky, making it difficult to observe astronomical objects. The spectral power distribution of artificial light sources is one of the key factors determining how much the night sky is deteriorated by light pollution. The ongoing replacement of discharge lamps with LED sources may have a major impact on astronomy because LED spectra usually cover the entire visible radiation range. This paper provides an analysis of the impact of LED sources with correlated color temperature in the range from 1000 K to approximately 10 000 K on visual and instrumental astronomical observations. For each analyzed artificial source, the Starlight Contamination Degree (SCD) index, i.e. a quantity that allows for quick evaluation of the impact of the sources on the night sky, is calculated. The reflection of artificial light from different ground surfaces and its scattering in the atmosphere was included in the calculation of the SCD index. LED lamps with very low values of correlated color temperature (CCT) and color rendering index (CRI) were found to possibly have a similar or even smaller impact on astronomical observations than sodium discharge lamps. Moreover, professional astronomical observations are more affected by LED lamps than visual observations, even for lamps with the lowest CCT and CRI. Thus, additional measures (e.g. reducing lumen output) should be applied to protect observational conditions. The results of the study help to assess which LED lamps can be used, and which should be avoided in the protection zones around astronomical observing sites. [ABSTRACT FROM AUTHOR]

In 1979, NASA established the Great Observatory program, which included four telescopes (Hubble, Compton, Chandra, and Spitzer) to explore the Universe. The Spitzer Space Telescope was launched in 2003 into solar orbit, gradually drifting away from the Earth. Spitzer was operated very successfully until 2020 when NASA terminated observations and placed the telescope in safe mode. In 2028, the U.S. Space Force has the opportunity to demonstrate satellite servicing by telerobotically reactivating Spitzer for astronomical observations, and in a separate experiment, carry out novel Space Weather research and operations capabilities by observing solar Coronal Mass Ejections. This will be accomplished by launching a small satellite, the Spitzer-Resurrector Mission (SRM), to rendezvous with Spitzer in 2030, positioning itself around it, and serving as a relay for recommissioning and science operations. A sample of science goals for Spitzer is briefly described, but the focus of this paper is on the unique opportunity offered by SRM to demonstrate novel Space Weather research and operations capabilities. [ABSTRACT FROM AUTHOR]

For the requirements of the multi-means observation and emergency monitoring of space objects, including space debris and near-earth asteroids, this paper analyzes the astronomical observation conditions in the stratosphere, which is the region of the earth's atmosphere between 18 km and 55 km of altitude. The results reveal that near space has a significantly superior sky background and observation environment than ground-based observation, with the values of transmittance in the visible band and near-infrared bands more than 0.91 and 0.988, respectively. The sky background radiance at 20 km is 2.5% of the ground in the visible band and near-infrared band, which is practical for daytime observation, and there is an advantage in the availability of observable hours without the influence of aerosols and turbulence, etc. Based on near-space aerostats, such as a high-altitude balloon, a new method of space object floating observation has been proposed, including the observation facilities and scheme. The simulation shows that it has an all-weather/all-day ability while adopting multi-band observation. Applying a telescope with 9.5 mag detective ability located on the aerostat, debris with the size of about 0.36 m can be observed at a 1000 km distance and phase angle of 100°, while the near-earth asteroid with the size of about 980 km can be observed at a 5 million km distance and phase angle of 40° during the daytime. With these advantages, the aerostat-based observation would be a beneficial supplement to the ground-based observation network. [ABSTRACT FROM AUTHOR]

In ground-based astronomical observations or artificial space target detections, images obtained from a ground-based telescope are severely distorted due to atmospheric turbulence. The distortion can be partially compensated by employing adaptive optics (pre-detection compensation), image restoration techniques (post-detection compensation), or a combination of both (hybrid compensation). This paper focuses on the improvement of the most commonly used practical post-processing techniques, Richardson–Lucy (R–L) iteration blind deconvolution, which is studied in detail and improved as follows: First, the total variation (TV) norm is redefined using the Gaussian gradient magnitude and a set scheme for regularization parameter selection is proposed. Second, the Gaussian TV constraint is proposed to impose to the R–L algorithm. Last, the Gaussian TV R–L (GRL) iterative blind deconvolution method is finally presented, in which the restoration precision is visually increased and the convergence property is considerably improved. The performance of the proposed GRL method is tested by both simulation experiments and observed field data. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The problem of sky pollution with artificial light currently affects practically all branches that are related to the broadly understood environment. This is especially true for astronomical observations. This paper presents the results of measurements of the surface brightness of the night sky for the city of Rzeszów and the surrounding area, which were made in 2015, 2018 and 2021 using the photometer Sky Quality Meter (SQM-L). The measurements show that the surface brightness of the night sky in Rzeszów in 2015 was in the range from 19.20 to 18.67 mag/arcsec2, in 2018 the value of brightness oscillated in the range from 18.53 to 16.47 mag/arcsec2, and in 2021 this value was in the range from 17.13 by 15.11 mag/arcsec2. Translating the obtained values on the Bortle scale, we can see an increase in the brightness of the night sky from class VI in 2015 to class IX in 2021. A similar trend applies to neighboring towns, for which an increase in brightness from class IV in 2015 to class VIII in 2021 was also observed. An increase in the surface brightness of the night sky causes a deterioration or even loss of visibility of astronomical objects in the night sky. This is especially true for comets and low-brightness stars. Based on the measurement results, a forecast of the development of light pollution was prepared for the study areas until 2025. This forecast shows that we will still have to deal with an increase in the surface brightness of the night sky. Due to the further projected increase in the brightness of the night sky, it should be expected that observers in small towns will experience changes in the quality of the sky over the coming years, which will undoubtedly make astronomical observations difficult, in particular for faint celestial bodies such as comets. [ABSTRACT FROM AUTHOR]

Context. Modern-day time-domain photometric surveys collect a lot of observations of various astronomical objects and the coming era of large-scale surveys will provide even more information on their properties. Spectroscopic follow-ups are especially crucial for transients such as supernovae and most of these objects have not been subject to such studies. Aims. Flux time series are actively used as an affordable alternative for photometric classification and characterization, for instance, peak identifications and luminosity decline estimations. However, the collected time series are multidimensional and irregularly sampled, while also containing outliers and without any well-defined systematic uncertainties. This paper presents a search for the best-performing methods to approximate the observed light curves over time and wavelength for the purpose of generating time series with regular time steps in each passband. Methods. We examined several light curve approximation methods based on neural networks such as multilayer perceptrons, Bayesian neural networks, and normalizing flows to approximate observations of a single light curve. Test datasets include simulated PLAsTiCC and real Zwicky Transient Facility Bright Transient Survey light curves of transients. Results. The tests demonstrate that even just a few observations are enough to fit the networks and improve the quality of approximation, compared to state-of-the-art models. The methods described in this work have a low computational complexity and are significantly faster than Gaussian processes. Additionally, we analyzed the performance of the approximation techniques from the perspective of further peak identification and transients classification. The study results have been released in an open and user-friendly Fulu Python library available on GitHub for the scientific community. [ABSTRACT FROM AUTHOR]

This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) —- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status of the instrumentation. We also present results of a transition observation, which offers unique measurements on several novel aspects. We estimate the RFI suppression required for such a radio astronomy instrumentation at the Moon-distances from Earth as order of − 80 dB. We analyse a method of separating Earth- and satellite-originated radio frequency interference (RFI). It is found that the RFI level at frequencies lower than a few MHz is smaller than the receiver noise floor. [ABSTRACT FROM AUTHOR]

This article is an obituary for Dr. Suzanne Virginie Débarbat, a prominent figure in French and international astronomy. She was born in France in 1928 and spent her entire career at the Paris Observatory, where she made significant contributions to the field of astrometry. Dr. Débarbat was also interested in the history of astronomy and published numerous books and research papers on the subject. She was an active member of the International Astronomical Union and served as President of the IAU Commission 41. Dr. Débarbat passed away in August 2024 at the age of 95. [Extracted from the article]

GPS radio occultations by Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) provide refractivity profiles, which are processed real-time to give profiles of temperature and water vapour in the lower atmosphere and electron density in the upper atmosphere. The new “atmPrf” (atmospheric profile) product gives temperature from surface to 0.2 hPa (~60 km). This is a dry temperature data product that does not include relative humidity in the inversion process and hence is reliable at and above the tropopause (>100 hPa) and erroneous in the troposphere (<100 hPa). In the current study we compare the COSMIC “atmPrf” data during December 2010 to November 2011 with other satellite (SABER/TIMED and MLS/Aura) temperatures from 50 to 0.2 hPa and reanalysis (NCEP, ERA-Interim and UKMO) outputs at 100, 10, 1 and 0.5 hPa pressure levels. The satellite comparisons show that the observed median differences are most likely produced due to the biases in the retrievals of SABER and MLS. When compared to re-analysis outputs, COSMIC seasonal means match NCEP and ECMWF seasonal mean temperatures very well, especially at 100 and 10 hPa. Comparison with radiosonde measured temperatures over Taipei (25° N, 121.5° E) in the lower altitudes also show very small differences. We conclude from this study that with the new COSMIC dry temperature retrievals obtained from radio occultations of GPS, there is a 20 km extension of reliable data in the middle atmosphere. “atmPrf” data are of good quality and provide reliable and unprecedentedly large number of profiles at greater temporal and spatial resolutions for further studies and investigations of the middle atmosphere up to 1 hPa, i.e., approximately up to the stratopause. [ABSTRACT FROM AUTHOR]

The article, the second in a series on the topic, examines British astronomer William Herschel's attempts to ascertain the true character of nebulae. Emphasis is given to his observations of planetary nebulae, with the author noting Herschel's discovery of the Saturn Nebula. His thoughts on the size of the Milky Way Galaxy are detailed, as are his cosmological theories on star clusters. The ways in which Herschel's discovery of true nebulosity influenced the development of his cosmogony are detailed as well.

The era of ime domain and multi-messenger astronomy is not only leading to the development of a much broader set of detectors and instruments for astrophysical observations, but is also providing the means for astronomy to tie directly to cutting-edge studies in physics. In this manner, fundamental physics (theory and experiment) coupled with a strong theoretical understanding of astrophysical phenomena (guided by high-performance computing simulations) can tie directly to the amazing new observations in astronomy. This paper discusses how physics, astrophysical models, and observations can not only help astronomy probe fundamental physics but guide the needs for next-generation astrophysical missions. [ABSTRACT FROM AUTHOR]

Galaxy observations suggest their stars move significantly faster than expected, given the total observable mass within these galaxies, hinting at a 'missing mass.' Of the several solutions to this missing mass problem, dark matter is the most supported explanation, solving the missing mass problem and agreeing with cosmological observations. This paper aims to highlight this missing mass problem, discuss potential solutions, and summarize current work on dark matter. I will highlight two classes of dark matter, cold and hot, and then discuss dark matter candidates. Finally, I summarize by discussing previous and ongoing experiments that search for these dark matter candidate particles. [ABSTRACT FROM AUTHOR]

The nature of equation of state for the matter in the neutron star plays an important role in determining its maximal mass. In addition, it must comply with the condition of causality. Noting that the central density of a maximally massive neutron star is well above the nuclear saturation density, a deconfined quark core in the central region is motivated in this paper. We analyze this scenario by employing the MIT bag model to represent the core region and one of the unified equations of state for the region outside the core. Such a combination is found to solve the problem of causality violation. In each case of the combined equations of state, the radial profile of ρ r 2 displays a peak and the dominant contribution to the total mass of the star comes from the region around the peak value of ρ r 2 , whereas the contribution is small from the regions near the center and the surface. This peak occurs in the region of hadronic matter for the combinations considered in this paper. Importantly, we find that the position of the peak in ρ r 2 is well-correlated with the maximal mass—the highest value of 1.98 M ⊙ obtains for the case with the peak occurring farthest from the center. This gravitational threshold being obtained for a non-rotating neutron star, we expect the threshold to lie well above 2 M ⊙ for a rapidly rotating neutron star, that may explain the existence of massive pulsars from recent astronomical observations. [ABSTRACT FROM AUTHOR]

The article profiles astronomer and post-doctoral student Joris De Ridder and his research of sound waves emitted from red giant stars. De Ridder and his research team use asteroseismology to measure variations in star brightness that reveal information about a star's makeup and age. The U.S. National Aeronautics and Space Agency has asked De Ridder to lead a red giant observation project using the Kepler telescope.

Focus accuracy is an essential factor that affects the quality of astronomical observations. The accurate measurement of celestial objects' properties depends on focus. Automatic focusing is necessary for celestial imaging systems. This paper presents a modified focus measure operator. It also proposes the use of fuzzy logic to transform images because of its tolerance of imprecise and incomplete data. The focus operators are applied to two sequences of star clusters' observations. The experimental results show that the suggested measure's overall score exceeds those of previous operators. [ABSTRACT FROM AUTHOR]

Due to its advantages of easy deployment and high stiffness-to-mass ratio, the utilization of truss structures for constructing large satellites presents an appealing solution for modern space missions, including Earth observation and astronomy. However, the dimensions of the traditional finite element model for a satellite with a large space truss structure become exceedingly large as the structure's size increases. The control system design process based on the finite element model is complex and time-consuming. This paper employs the continuum modeling method to represent the truss structure as a continuous entity. The bending vibrations of the truss structure are encapsulated by a simplified partial differential equation (PDE), as opposed to the more intricate traditional finite element model. Simultaneously, the satellite's attitude motion is characterized by an ordinary differential equation (ODE). Building upon this coupled PDE-ODE model, a boundary control law that only requires sensors/actuators at the boundary is formulated to effectively mitigate structural vibrations and regulate the satellite's attitude. The exponential stability of this closed-loop system is scrutinized using Lyapunov's direct method. The simulation results affirm that the continuum modeling method is indeed well-suited for satellites endowed with substantial truss structures, and the proposed boundary law proves to be highly effective in both attitude tracking and vibration suppression. [ABSTRACT FROM AUTHOR]

This paper outlines the efforts at establishing observatories in India for modern astronomical observations made by aristocrats over the last century or so prior to Indian independence in 1947. The focus of this paper is therefore on three institutions only, the Royal Observatory at Lucknow, Trevandrum Observatory, and Nizamiah Observatory in Hyderabad. This demonstrates that the concept of 'patronage' was alive and well in nineteenth century India, just as it was in Britain, Europe and North America. These observatories primarily were established either to encourage educated Indians to gain a realistic knowledge of Western astronomy, or so that India itself could contribute to that body of research knowledge. One of these institutions, Nizamiah Observatory was India's sole observatory involved in the ambitious international Astrographic Catalogue and Carte du Ciel and Project. It is telling that quite early in its history this Observatory ended up with a university, while this fate later befell Trevandrum Observatory. It is notable that none of the observatories discussed in this paper has survived in its original form through to the present day as a forefront astronomical research facility. Moreover, relatively early in its history Trevandrum Observatory abandoned astronomy and shifted its focus to geomagnetism. Unlike the observatories discussed in the first paper in this series, none of the observatories reviewed in this paper was set up primarily to further Britain's colonial ambitions. All were local Indian initiatives, yet each received support, in one way or another, from British astronomers or observatories--so the colonial link was still there, but only as an underlying element. [ABSTRACT FROM AUTHOR]

This paper outlines a multi-system approach for ground-based optical observations and the characterization of satellites in geostationary orbit. This multi-system approach is based on an in-depth analysis of the key factors to consider for light curve analysis of Earth's orbiting satellites. Light curves have been observed in different spectral bands using two different systems. The first system is specialized for astronomical observations and consists of a telescope equipped with an sCMOS camera and Sloan photometric filters. In contrast, the second system is a more cost-effective solution designed for professional non-astronomical applications, incorporating DSLR cameras equipped with RGB channels associated with a Bayer mask and photographic lenses. This comparative analysis aims to highlight the differences and advantages provided by each system, stressing their respective performance characteristics. The observed light curves will be presented as a function of the phase angle, which depends on the relative positions of the observer, the object, and the Sun. This angle plays an important role in optimizing the visibility of Earth's orbiting satellites. Finally, multiband observations of different satellites will be compared to seek an associated spectral signature, which may allow the identification of structurally similar objects through optical observations. [ABSTRACT FROM AUTHOR]

A sun photometer is a type of photometer that points at the sun, and it has been playing an increasingly important role in characterizing aerosols across the world. As long as the solar photometer is accurately calibrated, the optical thickness of the aerosol can be obtained from the measured value of this device. When the calibration of a single instrument is not accurate, the inversion quantity varies greatly. The calibration constant of the sun photometer changes during its use process; thus, calibrations are frequently needed in order to ensure the accuracy of the measured value. The calibration constant of the solar photometer is usually determined using the Langley method. Internationally, AERONET has two Langley calibration stations: the Mauna Loa observatory in the United States and the Izaña observatory in Spain. So far, the International Comparison and Calibration System has been established in Beijing, similar to AERONET at GSFC, but the Langley calibration system has not yet been established. Therefore, it is necessary to select a suitable calibration station in China. This paper studies the requirements of the calibration station using the Langley method. We used long-term records of satellite-derived measurements and survey data belonging to the aerosol optical thickness data of SNPP/VIIRS, CERES, MERRA-2, etc., in order to gain a better understanding of whether these stations are suitable for calibration. From the existing astronomical observation stations, meteorological stations, and the Sun–Sky Radiometer Observation Network (SONET) observation stations in China, the qualified stations were selected. According to the statistical data from the Ali observatory, the monthly average of clear sky is 20.21 days, and it is always greater than 15 days. The monthly average of aerosol is not more than 0.15 and is less than 0.3. We believe that the atmosphere above the Ali observatory is stable, and the results show that the Ali observatory has excellent weather conditions. This study can provide a selection of calibration sites for solar photometer calibrations in China that may need to be further characterized and evaluated, and at the same time provide a method to exclude unsuitable calibration sites. [ABSTRACT FROM AUTHOR]

Astronomical X-ray polarimetry was first explored in the end of the 1960s by pioneering rocket instruments. The craze arising from the first discoveries of stellar and supernova remnant X-ray polarization led to the addition of X-ray polarimeters to early satellites. Unfortunately, the inadequacy of the diffraction and scattering technologies required to measure polarization with respect to the constraints driven by X-ray mirrors and detectors, coupled with long integration times, slowed down the field for almost 40 years. Thanks to the development of new, highly sensitive, compact X-ray polarimeters in the beginning of the 2000s, observing astronomical X-ray polarization has become feasible, and scientists are now ready to explore our high-energy sky thanks to modern X-ray polarimeters. In the forthcoming years, several X-ray missions (rockets, balloons, and satellites) will create new observational opportunities. Interest in astronomical X-ray polarimetry field has thus been renewed, and this paper presents for the first time a quantitative assessment, all based on scientific literature, of the growth of this interest. [ABSTRACT FROM AUTHOR]

The Copernicus data Quality Control (CQC) is a service supporting the quality and harmonisation of satellite data offered to the Copernicus community. The CQC Team has recognised that there is variability of technical terms and definitions in the Earth Observation (EO) products in the context of the applied geometric corrections. A comparison among products from different missions suggests the need for a strong, co-ordinated harmonisation effort. This paper describes an activity of the CQC Team to encourage harmonisation among Copernicus data providers. For the time being this activity addresses only Optical imagery. Firstly, the paper clarifies a set of terms and relevant definitions for use within the paper itself and the published documentation at large. The choice of each term is driven by the fact that it is more broadly accepted by the scientific community than others. Then the paper describes the grouping (harmonization) of the products which have undergone the same (or similar) corrections into broad harmonised categories. Five classes are defined, i.e., Raw, Basic, Georeferenced, Georectified and Orthorectified: these can be considered as harmonised product types for all optical products offered on the EO market. [ABSTRACT FROM PUBLISHER]

In this paper we present the Spitzer IRS low-resolution observation for four candidates of Seyfert 1-like objects of ULIRGs from the SDSS-2dF-6dF sample. It is found that they are all real Seyfert 1-like objects because their infrared spectra are similar to that for Seyfert 1 source indicative of AGN nature, i.e. their spectra all show high-ionization lines of [NeV] at 14.32 μm and/or [SIV] at 10.51 μm in the mid-infrared. On the other hand, it is found that they also show PAH features at 6.2, 7.7, 8.6 and 11.25 μm indicative of star formation activity. In addition, it is found that they all show the silicate feature in absorption around 10 μm indicative of heavily material obscured these sources. Furthermore, some correlations among the far infrared colors, the line ratios, the equivalent widths (EWs) of PAH feature and the Silicate strengths are also discussed for these sources. [ABSTRACT FROM AUTHOR]

Blazars are the most numerous type of observed high-energy gamma-ray emitters. However, their emission mechanisms and population properties are still not well-understood. Crucial to this understanding are their cosmological redshifts, which are often not easy to obtain. This presents a great challenge to the next-generation ground-based observatory for very-high-energy gamma rays, the Cherenkov Telescope Array (CTA), which aims to detect a large number of distant blazars to study their intrinsic emission properties and to place tight constraints on the extragalactic background light density, amongst others. The successful investigation of these subjects needs a precise redshift determination. Motivated by these challenges, the CTA redshift task force initiated more than 3 years ago a spectroscopic observing program using some of the largest optical and infrared telescopes to measure the redshifts of a large fraction of blazars that are likely to be detected with CTA. In this proceedings, we give an overview of the CTA redshift task force, discuss some of the difficulties associated with measuring the redshifts of blazars and present our sample selection and observing strategies. We end the proceedings with reporting selected results from the program, the on-going collaborative efforts and our plans for the future. [ABSTRACT FROM AUTHOR]

In this paper, we construct a Schwarzschild metric in the fractal dimension based on fractal calculus, and we study the deflection of light near the sun. It was observed that the new fractal spherically symmetric spacetime metric may describe supermassive black holes, which have been detected through various astronomical observations such as SDSS. We have discussed the deflection of light by the gravitational field of the sun. It was observed that the total deflection of light is affected by the fractal dimension. To estimate the numerical value of the fractal dimension, we have used the 2004 analysis of almost 2 million VLBI observations of 541 radio sources made by 87 VLBI sites, which estimates the factor γ based on PNN formalism. It was observed that the fractal dimension is roughly less than unity. However, our analysis showed that large bending gravity gives fractal dimensions lower than unity to some extent. We also gave a naïve idea about the emission thermal Unruh process in fractal dimension. It was observed that both the temperature and the entropy of black holes are affected by the fractal dimension, and that for low numerical values, the entropy of the black hole is enhanced. [ABSTRACT FROM AUTHOR]

Insufficient theoretical investigation is being conducted on the spectroscopic characteristics within the infrared wavelength range of SiP, an identified interstellar molecule. Using the ic-MRCI method, potential energy functions and dipole moment functions for the ground state (⁠|${X^2}\Pi $|⁠) and low excited states (⁠|${{\rm{A}}^2}{\Sigma ^ + }$|⁠) of the SiP molecule were calculated. Based on experimental spectroscopy data, least squares fitting was used for the potential energy functions of the |${X^2}\Pi $| and |${{\rm{A}}^2}{\Sigma ^ + }$| states. By combining these potential energy and dipole moment functions, the one-dimensional Schrödinger equation was solved to obtain the vibronic energy levels and Einstein A coefficients for the electronic states. Partition functions of the SiP molecule from 0.1 to 3000 K and the radiative properties of |${X^2}\Pi \leftrightarrow {X^2}\Pi $| and |${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$| were derived. Infrared spectroscopy of the |${X^2}\Pi $| state and ultraviolet spectroscopy of the |${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$| transition at 100 K, a temperature crucial for astronomical research, were calculated. Results indicate that the spectral-line intensity of the |${X^{\rm{2}}}\Pi \leftrightarrow {{\rm{A}}^2}{\Sigma ^ + }$| transition is greater, making it more suitable for astronomical observation. The obtained computational results in this paper yield spectroscopic parameters for the characterization of the interstellar molecule SiP, furnishing theoretical underpinnings for subsequent experimental observations. [ABSTRACT FROM AUTHOR]

Featured Application: The Golay3 sparse aperture telescope designed in this paper can be carried on a satellite to realize Earth observation and remote sensing. A ground telescope with a larger aperture can also be designed with the method provided in this paper and used for astronomical observation. A Golay3 multi-mirror telescope (MMT) system is designed in this paper. The fill factor of the Golay3 MMT is derived from the angular resolution of the telescope. An initial configuration is established according to the paraxial optical theory. A three-element aspheric corrector group is designed and placed in the converging light cone to enlarge the field of view (FOV) of the Golay3 MMT. The tolerance analysis for each surface of the Golay3 MMT is conducted using the Monte Carlo method. The design results show the FOV of the Golay3 MMT system can be increased to 1.5° with the insertion of a three-element aspheric corrector group. The results of the tolerance analysis indicate that most tolerances are loose, while some decenter tolerances relating with the aspheric surfaces are relatively tight, but still within an acceptable range. [ABSTRACT FROM AUTHOR]

The Gemini High-resolution Optical SpecTrograph (GHOST) is the newest high-resolution spectrograph to be developed for a large-aperture telescope, recently deployed and commissioned at the Gemini-South telescope. In this paper, we present the first science results from the GHOST spectrograph taking during its commissioning runs. We have observed the bright metal-poor benchmark star HD 122563, along with two stars in the ultrafaint dwarf galaxy Reticulum II (Ret ii), one of which was previously identified as a candidate member, but did not have a previous detailed chemical abundance analysis. We find that this candidate (GDR3 0928) to be a bona fide member of Ret ii, and from a spectral synthesis analysis it is also revealed to be a CEMP- r star, with significant enhancements in several light elements (C, N, O, Na, Mg, and Si), in addition to featuring an r -process enhancement like many other Ret ii stars. The light-element enhancements in this star resemble the abundance patterns seen in the CEMP-no stars of other ultrafaint dwarf galaxies, and are thought to have been produced by an independent source from the r -process. These unusual abundance patterns are thought to be produced by faint supernovae, which may be produced by some of the earliest generations of stars. [ABSTRACT FROM AUTHOR]

Twenty years ago, we started to apply quantum optics to the astronomical research carried out inside the Department of Physics and Astronomy and the INAF Astronomical Observatory in Padova, Italy. The initial activities were stimulated by the project of the European Southern Observatory (ESO) to build a 100 m diameter telescope, the Overwhelmingly Large (OWL) telescope. The enormous photon flux expected from such an aperture suggested that quantum optics concepts be utilized in order to obtain novel astrophysical results. Following initial successful attempts to utilize the orbital angular momentum of the light beam to enhance the visibility of faint companions to bright stars, the Padova team concentrated its efforts on very high time resolution, in order to measure and store the arrival time of celestial photons to better than one nanosecond. To obtain observational results, we built two photon counting photometers (AquEye and IquEye) to be used with our telescopes of the Asiago Observatory and with 4 m class telescopes such as the ESO New Technology Telescope (NTT) in Chile. This paper firstly describes these two instruments and then expounds the results obtained on pulsar light curves, lunar occultations and the first photon counting intensity interferometry measurements of the bright star Vega. Indeed, the correlation of photon arrival times on two or more apertures can lead to extremely high angular resolutions, as shown around 1970 by Hanbury Brown and Twiss. Prospects for quantum intensity interferometry with arrays of Cherenkov light telescopes will also be described. [ABSTRACT FROM AUTHOR]

In this paper, we describe the optical alignment method for the Prime-focus-Infrared Microlensing Experiment (PRIME) telescope which is a prime-focus near-infrared (NIR) telescope with a wide field of view for the microlensing planet survey toward the Galactic center that is the major task for the PRIME project. There are three steps for the optical alignment: preliminary alignment by a laser tracker, fine alignment by intra- and extra-focal (IFEF) image analysis technique, and complementary and fine alignment by the Hartmann test. We demonstrated that the first two steps work well by the test conducted in the laboratory in Japan. The telescope was installed at the Sutherland Observatory of South African Astronomical Observatory in August, 2022. At the final stage of the installation, we demonstrated that the third method works well and the optical system satisfies the operational requirement. [ABSTRACT FROM AUTHOR]