We present a new algorithm to solve the equations of radiation hydrodynamics (RHD) in a frequency-integrated, two-moment formulation. Novel features of the algorithm include i) the adoption of a non-local Variable Eddington Tensor (VET) closure for the radiation moment equations, computed with a ray-tracing method, ii) support for adaptive mesh refinement (AMR), iii) use of a time-implicit Godunov method for the hyperbolic transport of radiation, and iv) a fixed-point Picard iteration scheme to accurately handle the stiff nonlinear gas-radiation energy exchange. Tests demonstrate that our scheme works correctly, yields accurate rates of energy and momentum transfer between gas and radiation, and obtains the correct radiation field distribution even in situations where more commonly used – but less accurate – closure relations like the Flux-limited Diffusion and Moment-1 approximations fail. Our scheme presents an important step towards performing RHD simulations with increasing spatial and directional accuracy, effectively improving their predictive capabilities.

The LIGO-Virgo gravitational wave detectors have confidently observed 4 events involving neutron stars: two binary neutron star (BNS) mergers (GW170817 and GW190425), and two neutron star-black hole mergers (GW200105 and GW200115). However, our theoretical understanding of the remnant properties of such systems is incomplete due to the complexities related to the modeling of matter effects and the very high computational cost of corresponding numerical relativity simulations. An important such property is the recoil velocity, which is imparted onto the remnant due to the anisotropic emission of gravitational radiation and the dynamical ejection of matter in the kilonova. In this work, we combine gravitational radiation as well as dynamical ejecta distributions, computed by the Computational Relativity numerical simulations, to get accurate estimates for BNS remnant recoil velocities. We find that recoils due to ejection of matter dominate those caused by gravitational wave emission. Knowledge of BNS remnant recoil velocities is important in determining if the remnant is retained by its environment for future hierarchical mergers which, in turn, can form binaries with black holes in the so-called lower mass gap of ∼ 3 – 5M⊙.

Due to the rich phenomenology and extreme magnetic conditions, magnetars will be targets of great interest for the upcoming polarimetry space missions. In particular, the Imaging X-ray Polarimetry Explorer (IXPE), recently launched in December 2021, will operate in the 2–8 keV range. This will open a new window to study the polarized, persistent X-ray emission from magnetars. In this talk, I will present simulations of IXPE observations of magnetars using the IXPEObsSim package. I will discuss future prospect to discriminate between different magnetar’s emission mechanisms, as well as a potential detection of the signal of vacuum birefringence using IXPE.

The dense matter equation of state (EoS), describing the state of matter under the extreme conditions found in neutron stars, is not accurately known. However, significant process has been made in recent years through the emergence of new observational avenues of neutron stars. Firstly, the X-ray timing telescope NICER has delivered two joint mass-radius measurements, for pulsars PSR J0030+0451 and PSR J0740+6620, using pulse profile modeling. Secondly, gravitational wave detections of binary neutron star (BNS) mergers allow for a measurement of the EoS-dependent tidal deformability, as demonstrated in the first detected BNS merger GW170817. Additionally, electromagnetic radiation from the subsequent ultraviolet-optical-infrared transient (the kilonova) originating from the ejected material in GW170817 further probes the binary system and the EoS. We demonstrate how the joint analysis of these multi-messenger observations of neutron stars significantly constrains the dense matter EoS. We then describe, in more detail, a framework to jointly analyse a gravitational wave signal and the accompanying kilonova light curves, focusing on possible future black hole–neutron star (BHNS) mergers. We highlight the potential for multimessenger BHNS to constrain the tidal deformability of the neutron star, thereby increasing our understanding of the dense matter EoS.

The progress of cosmic reionization depends on the presence of over-dense regions that act as photon sinks. Such sinks may slow down ionization fronts as compared to a uniform intergalactic medium (IGM) by increasing the clumping factor. We present simulations of reionization in a clumpy IGM resolving even the smallest sinks. The simulations use a novel, spatially adaptive and efficient radiative transfer implementation in the SWIFT SPH code, based on the two-moment method. We find that photon sinks can increase the clumping factor by a factor of ∼10 during the first ∼100 Myrs after the passage of an ionization front. After this time, the clumping factor decreases as the smaller sinks photoevaporate. Altogether, photon sinks increase the number of photons required to reionize the Universe by a factor of η ∼2, as compared to the homogeneous case. The value of η also depends on the emissivity of the ionizing sources.

Vortices are patches of fluid revolving around a central axis. They are ubiquitous in fluid dynamics. To the human eye, detecting vortices is a trivial task thanks to our inherent ability to identify patterns. To solve this task automatically, we developed the Vortector pipeline which was used to identify and characterize vortices in around one million snapshots of planet-disk interaction simulations in the context of planet formation. From the emergence of two regimes of vortex lifetime, one of which shows very long-lived vortices, we conclude that future resolved disk observations will predominantly detect vortices in the outer parts of protoplanetary disks.

GW170817, the merger of two neutron stars witnessed through both its gravitational wave siren and its glow at all wavelengths of light, represents the first multi-messenger detection of a compact binary merger. The association of the GW in-spiral signal from GW170817 with a γ-ray burst, a kilonova, and a non-thermal afterglow spanning all bands of the electromagnetic spectrum, has provided rich constraints on the physics and astrophysics of neutron stars. Starting from the example of GW170817, I briefly summarize recent results on observations of electromagnetic afterglows from gravitational wave triggers. In the light of these results, I highlight some key questions that are yet to be answered after the GW170817 discovery. I conclude by commenting briefly on some opportunities that lie in front of us, as improvements in ground-based gravitational wave detectors’ sensitivities will transform a trickle of multi-messenger discoveries into a flood, bringing the field of gravitational wave astronomy from its infancy to its maturity.

In this article we describe the recent history of astronomy in South Africa from the perspective of development. We describe how all major astronomy initiatives have carried a component of development with them, be it capacity building or socio-economic development. We highlight some activities and conclude that South Africa’s coherent and ambitious strategy has led to substantial changes in the astronomy research community in South Africa and that the young astronomers now starting their careers are taking possession of a bright future.

History, Maths and Astronomy are all mixed up in an innovative educational project that is being carried out in the Faculty of Education of the Universidad de La Laguna, in Spain. Students learn how to teach (to primary school students) about the shape of the Earth, the distances to the Moon, the Sun and other planets, collecting their own data with simple instrumentation and, most important, to connect ideas and different disciplines. The structure and contents of this project are presented, as well as examples of the activities that are carried out.

Traditional visual aids used in astronomy outreach (such as 2D telescope images) can fail to effectively convey complex and abstract ideas to lay audiences. With the advent of impressive CGI images widely available in film and other media, these aids may also not meet their expectations or visually engage people. To address this, we have been employing 3D holograms in lieu of 2D images for astronomy-based outreach activities both in-person (pre-pandemic), and virtually since the start of the pandemic. Here we demonstrate how the reader can make and incorporate holograms in their own virtual talks (no budget required) and present the feedback we’ve received so far.

On the occasion of celebration of moon landing (2019) we designed a set of educational activities for the youngest, based on the moon. We wanted to talk, play and engage young people reflecting and enjoying different points of view and demystifying the idea of science and scientists in a personal and meaningful journey. After this year of experimentation we also engaged with public schools co-designing and tailoring those activities despite the current sanitarian crisis. We will describe a physical artifact called ‘Lunatario’ and its 3d printable version together with cross-disciplinary educational activities and our tentative documentation. We will also describe how, with the help of a very diverse team, we embedded other media in our moon exploration working in particular with picture books and animation. We believe this is a great way to deeply engage young people with STEAM in a democratic way.

We here present the general outline of the project “Open up, Sky!”, a pilot project of astronomy education in a Juvenile detention institution in Sardinia, Italy. The project is still in progress, and we report here the first preliminary results.

We present recommendations for teachers and educators of science, based on the results of a survey carried out among secondary-school students from Poland, Australia, and the USA.

Girls’ under-representation in science, technology, engineering and mathematics (STEM) education is deep rooted and puts a detrimental brake on progress towards sustainable development. Both education and gender equality are an integral part of the 2030 Agenda for Sustainable Development, adopted by the United Nations General Assembly in 2015, as distinct Sustainable Development Goals (SDGs). The UNESCO Report: Cracking the code: Girls’ and women’s education in STEM provides a global snapshot of this underrepresentation and the factors behind it. The fight against stereotypes to ‘crack the code’, or to decipher the factors that hinder or facilitate girls’ and women’s participation in STEM (and particularly in Astronomy) education must take into account the persisting dichotomy between the so called two cultures.

This paper provides a brief overview of the many facets of astronomy education and heritage, and how the IAU stimulates them. Activities range from training in astronomy through scientific meetings and schools for young astronomers, to using astronomy as a tool for development and for stimulating science education at school level. Communicating astronomy with the public and engaging in outreach activities with children to inspire curiosity is yet another way of how astronomy can help build a literate society and install a sense of global citizenship. The involvement of many people at all levels is key to success.

With this roundtable we wished to discuss about different topics related to research, innovation, scientific literacy and inclusion in Astronomy education, putting together the expertise of educators from all around the world. The present paper includes the introduction to the roundtable prepared by the chairs of the session as well as the contributions from several of the participants.

This contribution summarizes the reconstruction of historical constellations. It is based on studies of classics, philologies, history of science and history of art. In the given brevity, I can only sketch the strategic, scientific and educational reasons.

Interdisciplinary and egalitarian, the School Workshops on Astronomy have been being in their educational mission since 14 years. Here we present the concept, methods, and some example results of that educational technique.

Namibia is world-renowned for its incredibly dark skies by the astronomy community, and yet, the country is not well recognised as a dark sky destination by tourists and travellers. Forged by a collaboration between the Universities of Oxford and Namibia, together we are using astronomy as a means for capacity-building and sustainable socio-economic growth via educating tour guides and promoting dark sky tourism to relevant stakeholders.

When we talk about Astronomy, we normally do not take into account that we are using a cultural specific way of understanding the sky. Astronomers, either professional, amateur or just lovers of the sky nowadays tend to approach the sky from the point of view of modern science. There, we approach the sky as something that needs to be explored, understood and explained.

However, this vision was not always like that, or even in other cultures is/was completely different. For centuries, the human being has comprehended the sky, its changes and constancies, as part of their world, as part of the environment, as part of their everyday life.

In this paper, I review a few of these different ways of approaching the sky in several cultures, from the Near East to Rome or the Andes and how we can use them today for education, outreach and heritage management.