Astronomical Community Research Articles

‘The grand strategy of an observatory’: George Airy's vision for the division of astronomical labour among observatories during the nineteenth century

The downfall of the Parramatta Observatory during the 1840s led the British Government to reconsider the funding it provided to observatories. George Biddell Airy—the Astronomer Royal at the Royal Observatory, Greenwich—recommended the establishment of a central Colonial Board of Visitors (based in London) to oversee the management of observatories within the British Empire. The recommendation ultimately never materialized, but it showcased the support of the astronomical community and the British Government for centralizing the management of the vast network of observatories. This centralized vision continued to influence the founding of new observatories and the organization of their work. The article examines Airy's vision of a centralized organization of division of labour among observatories through his involvement in the discussions about the Colonial Board of Visitors. It also examines how he continued supporting the same vision through articles about the work of observatories, and through written advice about establishing observatories. The article demonstrates how he envisioned the grand strategy of an observatory to encompass public utility while also fitting it within the general policy of observatories in relation to the division of astronomical labour.

Using Cosmic Rays Detected by HST as Geophysical Markers. I. Detection and Characterization of Cosmic Rays

Abstract The Hubble Space Telescope (HST) has been operational for over 30 years, and throughout that time it has been bombarded by high-energy charged particles colloquially referred to as cosmic rays. In this paper, we present a comprehensive study of more than 1.2 billion cosmic rays observed with HST using a custom-written Python package, HSTcosmicrays, that is available to the astronomical community. We analyzed 75,908 dark calibration files taken as part of routine calibration programs for five different CCD imagers with operational coverage of Solar Cycle 23 and 24. We observe the expected modulation of galactic cosmic rays by solar activity. We model the observed energy-loss distributions to derive an estimate of 534 ± 117 MeV for the kinetic energy of the typical cosmic ray impacting HST. For the three imagers with the largest nonuniformity in thickness, we independently confirm the overall structure produced by fringing analyses by analyzing cosmic ray strikes across the detector field of view. We analyze STIS/CCD observations taken as HST crosses over the South Atlantic Anomaly and find a peak cosmic ray particle flux of ∼1100 particle s−1 cm−2. We find strong evidence for two spatially confined regions over North America and Australia that exhibit increased cosmic ray particle fluxes at the 5σ level.

Real-time multi-messenger analysis framework for KM3NeT

KM3NeT is a multi-purpose cubic-kilometer neutrino observatory under construction in the Mediterranean Sea. It consists of ORCA and ARCA (for Oscillation and Astroparticle Research with Cosmics in the Abyss, respectively), currently both have a few detection lines in operation. Although having different primary goals, both detectors can be used for neutrino astronomy over a wide energy range, from a few tens of MeVs to a few tens of PeV. In view of the growing field of time-domain astronomy, it is crucial to be able to identify neutrino candidates in real-time. This online neutrino sample will allow triggered neutrino alerts that will be sent to the astronomy community and to look for time/space coincidences around external electromagnetic and multi-messenger triggers. These real-time searches can significantly increase the discovery potential of transient cosmic accelerators and refine the pointing directions in the case of poorly localized triggers, such as gravitational waves. In the field of core-collapse supernovae (CCSN), the detection of the MeV-scale CCSN neutrinos is crucial as an early warning of the electromagnetic follow-up. KM3NeT's digital optical modules act as good detectors for these supernovae neutrinos. This proceeding presents the status of KM3NeT's real-time multi-messenger activities, including online event reconstruction, event classification and selection, alert distribution, and supernova monitoring.

Models of representing an astronomer’s voice in a journalist’s popular judgment

Within the framework of this article, the starting point of the research is the theoretical position, according to which reports on discoveries and achievements in the field of astronomy appear as a frequency phenomenon, covered in specialized popular scientific texts. As a result, a pragmatic analysis of the source of information and ensuring access to the voices of astronomer researchers in a journalistic report is an urgent problem. The personality of the journalist acts as an intermediary between scientists and non-professional readers, whose knowledge of astronomy is limited, and the created popular science texts are a kind of communication platform for voicing the judgments that are put forward by representatives of the astronomical communities. In this regard, journalists not only supplement the reader’s knowledge in an accessible form, but also open access to the voices of representatives of the scientific and astronomical community, relying on such means as direct and indirect speech, which reveal different degrees of frequency in the first paragraph of the text and in the subsequent presentation. To systematize the actual data indicating the explicit labeling of the source of information in a popular science message, the most frequent language signals that are used by journalists in order to introduce a «foreign» voice into the text (predicates that introduce direct or indirect speech) are analyzed. As a result, models and indicators of their frequency were identified, this, in turn, provided an opportunity to trace the trends in voicing the expert astronomers’ opinions in a popular scientific text. It is established that the distribution of direct and indirect speech with explicit marking of the source of information in the first paragraph of the popular science text is not homogeneous. In this text segment, indirect speech is the most frequent, which allows the journalist to focus the reader’s attention on an unbiased vision of a scientific and astronomical event.

The correct sense of Faraday rotation

ABSTRACT The phenomenon of Faraday rotation of linearly polarized synchrotron emission in a magneto-ionized medium has been understood and studied for decades. But since the sense of the rotation itself is irrelevant in most contexts, some uncertainty and inconsistencies have arisen in the literature about this detail. Here, we start from basic plasma theory to describe the propagation of polarized emission from a background radio source through a magnetized, ionized medium in order to re-derive the correct sense of Faraday rotation. We present simple graphics to illustrate the decomposition of a linearly polarized wave into right and left circularly polarized modes, the temporal and spatial propagation of the phases of those modes, and the resulting physical rotation of the polarization orientation. We then re-examine the case of a medium that both Faraday rotates and emits polarized radiation and show how a helical magnetic field can construct or destruct the Faraday rotation. This paper aims to resolve a source of confusion that has arisen between the plasma physics and radio astronomy communities and to help avoid common pitfalls when working with this unintuitive phenomenon.

TRAPPIST Habitable Atmosphere Intercomparison (THAI) Workshop Report

Abstract The era of atmospheric characterization of terrestrial exoplanets is just around the corner. Modeling prior to observations is crucial in order to predict the observational challenges and to prepare for the data interpretation. This paper presents the report of the TRAPPIST Habitable Atmosphere Intercomparison workshop (2020 September 14–16). A review of the climate models and parameterizations of the atmospheric processes on terrestrial exoplanets, model advancements, and limitations, as well as direction for future model development, was discussed. We hope that this report will be used as a roadmap for future numerical simulations of exoplanet atmospheres and maintaining strong connections to the astronomical community.

Deep learning Blazar classification based on multifrequency spectral energy distribution data

ABSTRACT Blazars are among the most studied sources in high-energy astrophysics as they form the largest fraction of extragalactic gamma-ray sources and are considered prime candidates for being the counterparts of high-energy astrophysical neutrinos. Their reliable identification amid the many faint radio sources is a crucial step for multimessenger counterpart associations. As the astronomical community prepares for the coming of a number of new facilities able to survey the non-thermal sky at unprecedented depths, from radio to gamma-rays, machine-learning techniques for fast and reliable source identification are ever more relevant. The purpose of this work was to develop a deep learning architecture to identify Blazar within a population of active galactic nucleus (AGN) based solely on non-contemporaneous spectral energy distribution information, collected from publicly available multifrequency catalogues. This study uses an unprecedented amount of data, with spectral energy distributions (SEDs) for ≈14 000 sources collected with the Open Universe VOU-Blazars tool. It uses a convolutional long short-term memory neural network purposefully built for the problem of SED classification, which we describe in detail and validate. The network was able to distinguish Blazars from other types of active galactic nuclei (AGNs) to a satisfying degree (achieving a receiver operating characteristic area under curve of 0.98), even when trained on a reduced subset of the whole sample. This initial study does not attempt to classify Blazars among their different sub-classes, or quantify the likelihood of any multifrequency or multimessenger association, but is presented as a step towards these more practically oriented applications.

Communicating astronomy with the public: perspectives of an international community of practice

Communities of practice in science communication can make important contributions to public engagement with science but are under-researched. In this article, we look at the perspectives of a community of practice in astronomy communication regarding (relations with) their public(s). Most participants in this study consider that public(s) have several deficits and vulnerabilities. Moreover, practitioners have little to no contact with (and therefore make no use of) academic research on science communication. We argue that collaboration between science communication researchers and practitioners could benefit the science-public relationship and that communities of practice may be critical to that purpose.

Jan Walery Jędrzejewicz (1835–1887) and his Observations of Comets

Jan Walery Jędrzejewicz was a medical doctor with active practice in Płońsk and an astronomer by passion. In fact, astronomy was a second profession for ‘Dr. Jedrzejewicz’, as he signed his astronomical publications. He built his own observatory in Płońsk, small village situated about 70 km from Warsaw, which he equipped with professional instruments. Thanks to that, he could perform precise astronomical observations. In the astronomical community, he was known and esteemed for his precise measurements of double stars. He also measured the position of many comets discovered at that times, including long-period ones. This study is devoted to the analysis of precision of Jędrzejewicz measurements on the examples of three long-period comets, today known as C/1885 X1 Fabry, C/1885 X2 Barnard and C/1886 T1 Barnard-Hartwig.

Hackathons catch on for creativity, education, and networking

Physics and astronomy communities take a page from data-science and tech worlds to hold events of feverish teamwork.

New books & media

New books & media

Contribution of statistical site learning to improve optical turbulence forecasting

ABSTRACT The forecast for atmospheric and turbulence conditions above astronomical observatories is of interest to the astronomical community because it allows observations to be planned with maximum efficiency, a process called flexible scheduling. It can also be used to simulate long-term site testing to provide local information useful for the conception of focal and post-focal instrumentation. We have presented our forecasting tool in previous publications, but in this paper we focus on the importance of using local measurements to improve the predictive turbulence model and to better consider the local specificities of a given site, a process we call site learning. For this study, we use a local data base provided by the Calern Atmospheric Turbulence Station, which has been operational since 2015 at Calern Observatory. In addition, we use a set of several months of predictions to feed the turbulence model, taking into account daytime and nighttime conditions. This upgrade improves the quality of our forecasting by reducing the absolute bias between measurements and predictions from 25 to 50 per cent for each layer of the $C_n^2$, by 25 per cent for the seeing, and by 70 per cent for the isoplanatic angle.

Painlevé–Gullstrand form of the Lense–Thirring Spacetime

The standard Lense–Thirring metric is a century-old slow-rotation large-distance approximation to the gravitational field outside a rotating massive body, depending only on the total mass and angular momentum of the source. Although it is not an exact solution to the vacuum Einstein equations, asymptotically the Lense–Thirring metric approaches the Kerr metric at large distances. Herein we shall discuss a specific variant of the standard Lense–Thirring metric, carefully chosen for simplicity, clarity, and various forms of improved mathematical and physical behaviour, (to be more carefully defined in the body of the article). We shall see that this Lense–Thirring variant can be viewed as arising from the linearization of a suitably chosen tetrad representing the Kerr spacetime. In particular, we shall construct an explicit unit-lapse Painlevé–Gullstrand variant of the Lense–Thirring spacetime, one that has flat spatial slices, a very simple and physically intuitive tetrad, and extremely simple curvature tensors. We shall verify that this variant of the Lense–Thirring spacetime is Petrov type I, (so it is not algebraically special), but nevertheless possesses some very straightforward timelike geodesics, (the “rain” geodesics). We shall also discuss on-axis and equatorial geodesics, ISCOs (innermost stable circular orbits) and circular photon orbits. Finally, we wrap up by discussing some astrophysically relevant estimates, and analyze what happens if we extrapolate down to small values of r; verifying that for sufficiently slow rotation we explicitly recover slowly rotating Schwarzschild geometry. This Lense–Thirring variant can be viewed, in its own right, as a “black hole mimic”, of direct interest to the observational astronomy community.

Identifying and Analyzing Astronomers' Preferences for the Next Decade of NASA

The aim of this research is to survey preferences in the astronomy and astrophysics community as they relate to the next decade of NASA. Preferences are key for understanding how decisions are made by individuals that could aid in projecting community preferences and likely outcomes. The study was performed using a survey methodology and evaluated preferences regarding the decadal survey by prioritizing space-based astrophysics missions and research activities. Thematic analysis was implemented to determine themes within participants' open survey responses. Our results show strong community preferences for observational astronomy and science versatility, capability, and scientific return for the upcoming decadal period. Moreover, our findings also show consensus among subgroups in the community. We elaborate on community preferences by presenting results on mission concepts, mission capabilities, and primary science that NASA should strategically invest in.

How not to obtain the redshift distribution from probabilistic redshift estimates: Under what conditions is it not inappropriate to estimate the redshift distribution N(z) by stacking photo- z PDFs?

The scientific impact of current and upcoming photometric galaxy surveys is contingent on our ability to obtain redshift estimates for large numbers of faint galaxies. In the absence of spectroscopically confirmed redshifts, broad-band photometric redshift point estimates (photo-$z$s) have been superseded by photo-$z$ probability density functions (PDFs) that encapsulate their nontrivial uncertainties. Initial applications of photo-$z$ PDFs in weak gravitational lensing studies of cosmology have obtained the redshift distribution function $\mathcal{N}(z)$ by employing computationally straightforward stacking methodologies that violate the laws of probability. In response, mathematically self-consistent models of varying complexity have been proposed in an effort to answer the question, "What is the right way to obtain the redshift distribution function $\mathcal{N}(z)$ from a catalog of photo-$z$ PDFs?" This letter aims to motivate adoption of such principled methods by addressing the contrapositive of the more common presentation of such models, answering the question, "Under what conditions do traditional stacking methods successfully recover the true redshift distribution function $\mathcal{N}(z)$?" By placing stacking in a rigorous mathematical environment, we identify two such conditions: those of perfectly informative data and perfectly informative prior information. Stacking has maintained its foothold in the astronomical community for so long because the conditions in question were only weakly violated in the past. These conditions, however, will be strongly violated by future galaxy surveys. We therefore conclude that stacking must be abandoned in favor of mathematically supported methods in order to advance observational cosmology.

Simulated Sky

For centuries, the rich nocturnal environment of the starry sky could be modelled only by analogue tools such as paper planispheres, atlases, globes and numerical tables. The immersive sky simulator of the twentieth century, the optomechanical planetarium, provided new ways for representing and teaching about the sky, but the high construction and running costs meant that they have not become common. However, in recent decades, “desktop planetarium programs” running on personal computers have gained wide attention. Modern incarnations are immensely versatile tools, mostly targeted towards the community of amateur astronomers and for knowledge transfer in transdisciplinary research. Cultural astronomers also value the possibilities they give of simulating the skies of past times or other cultures. With this paper, we provide an extended presentation of the open-source project Stellarium, which in the last few years has been enriched with capabilities for cultural astronomy research not found in similar, commercial alternatives.

(Un)conscious Bias in the Astronomical Profession: Universal Recommendations to improve Fairness, Inclusiveness, and Representation

(Un)conscious bias affects every aspect of the astronomical profession, from scientific activities (e.g., invitations to join collaborations, proposal selections, grant allocations, publication review processes, and invitations to attend and speak at conferences) to activities more strictly related to career advancement (e.g., reference letters, fellowships, hiring, promotion, and tenure). For many, (un)conscious bias is still the main hurdle to achieving excellence, as the most diverse talents encounter bigger challenges and difficulties to reach the same milestones than their more privileged colleagues. Over the past few years, the Space Telescope Science Institute (STScI) has constructed tools to raise awareness of (un)conscious bias and has designed guidelines and goals to increase diversity representation and outcome in its scientific activities, including career-related matters and STScI sponsored fellowships, conferences, workshops, and colloquia. STScI has also addressed (un)conscious bias in the peer-review process by anonymizing submission and evaluation of Hubble Space Telescope (and soon to be James Webb Space Telescope) observing proposals. In this white paper we present a plan to standardize these methods with the expectation that these universal recommendations will truly increase diversity, inclusiveness and fairness in Astronomy if applied consistently throughout all the scientific activities of the Astronomical community.

The Scientific Impact of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) for Solar System Science

Vera C. Rubin Observatory will be a key facility for small body science in planetary astronomy over the next decade. It will carry out the Legacy Survey of Space and Time (LSST), observing the sky repeatedly in u, g, r, i, z, and y over the course of ten years using a 6.5 m effective diameter telescope with a 9.6 square degree field of view, reaching approximately r = 24.5 mag (5-{\sigma} depth) per visit. The resulting dataset will provide extraordinary opportunities for both discovery and characterization of large numbers (10--100 times more than currently known) of small solar system bodies, furthering studies of planetary formation and evolution. This white paper summarizes some of the expected science from the ten years of LSST, and emphasizes that the planetary astronomy community should remain invested in the path of Rubin Observatory once the LSST is complete.

Origins Space Telescope science drivers to design traceability

The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K- and M-dwarfs to identify potentially habitable—and even inhabited—worlds. These science priorities are aligned with NASA’s three major astrophysics science goals: How does the Universe work? How did we get here? and Are we alone? We briefly describe the science case that arose from the astronomical community and the science traceability matrix for Origins. The science traceability matrix prescribes the design of Origins and demonstrates that it will address the key science questions motivated by the science case.

Jupyter-Enabled Astrophysical Analysis Using Data-Proximate Computing Platforms

The advent of increasingly large and complex datasets has fundamentally altered the way that scientists conduct astronomy research. The need to work closely to the data has motivated the creation of online science platforms, which include a suite of software tools and services, therefore going beyond data storage and data access. We present two example applications of Jupyter as a part of astrophysical science platforms for professional researchers and students. First, the Astro Data Lab is developed and operated by NOIRLab with a mission to serve the astronomy community with now over 1500 registered users. Second, the Dark Energy Spectroscopic Instrument science platform serves its geographically distributed team comprising about 900 collaborators from over 90 institutions. We describe the main uses of Jupyter and the interfaces that needed to be created to embed it within science platform ecosystems. We use these examples to illustrate the broader concept of empowering researchers and providing them with access to not only large datasets but also cutting-edge software, tools, and data services without requiring any local installation, which can be relevant for a wide range of disciplines. Future advances may involve science platform networks, and tools for simultaneously developing Jupyter notebooks to facilitate collaborations.