Water, an essential molecule for sustaining life on Earth, plays a crucial role in the physical and chemical processes governing the formation of stars and planets, serving as a primary coolant in the environments surrounding emerging stars. The journey of water from the earliest stages of star and planet formation to its eventual incorporation to exoplanetary atmospheres and its potential oceans is still a matter of debate. Very recent works using ALMA and JWST data reveals that water can be found in the inner astronomical units in protoplanetary disks, in the terrestrial planet-forming zone. Detecting water molecules from ground-based telescopes is challenging due to the water vapor content within Earth’s atmosphere, severely limiting atmospheric transmissivity. Nevertheless, water is one of the few compounds capable of generating bright maser emission within star-forming regions. Their exceptional brightness, narrow spectral profiles, and their origin in highly compact regions offer a unique set of characteristics that render them invaluable tools for investigating circumstellar structure and dynamics at sub-arcsecond spatial scales. In this work we present our efforts to search and characterize water maser emission at submillimeter frequencies in a sample of young stellar objects.

Until now, there has been no evidence of the existence of life forms other than on Earth. The philosophical, ethical and theological corpus that has been built up on this subject over several millennia is therefore based on a thought experiment or a posture of belief. Between dealing with a heresy and applying the precautionary principle, extraterrestrials represent a special opportunity to question the boundaries of our systems of thought, and sometimes to shake up dogmatism.

We consider the dynamic evolution of the compact four-planetary system K2-72. We considered a few scenarios for the evolution of the K2-72 system over 100 Myr using the Posidonius software, which considers tidal interactions. We showed that the compact planetary system K2-72 likely evolves beyond low-order resonances. A significant change in the large semi-major axes of the orbits of the K2-72 b and K2-72 d planets leads to the moving of the adjacent planets b-d and d-c out of the 7/5 and 8/5 resonance regions, respectively. The adjacent planets K2-72 d and K2-72 c are located far from the 2/1 resonance, which excludes the possibility of forming chains of mean motion resonances and, hence, 3-planet mean motion resonances. If the orbital eccentricities do not exceed 0.03, the evolution of the compact planetary system K2-72 over 100 Myr remains stable even in the presence of tidal perturbations.

Telkom-1 is a geosynchronous communications satellite owned by telecommunications company, PT Telkom Indonesia. This paper will discuss solar radiation pressure as one of the most significant perturbations in geostationary orbits. Solar radiation pressure models come in various types, each differing in complexity and accuracy. The simplest solar radiation pressure model is a spherical model, often used for educational or preliminary calculations. Based on our modelling, the results indicate that the semimajor axis values from the spherical model closely approximate the actual data. However, the eccentricity calculated from the spherical model is nearly ten times larger than that derived from the actual data. Additionally, the amplitude of the mean anomaly from the spherical model increases over time, and the spherical model of inclination also demonstrates an increasing trend with time.

The growing international public attention to astrobiology and SETI, combined with the immense costs of space exploration and the potential outcome, the discovery of extraterrestrial life, will likely increase the pressure for public justification and the need to address societal concerns about the risks of searching for, finding, or being found by extraterrestrial life. Understanding these perceptions and concerns warrants a more systematic inclusion of risk communication research in studying pre- and post-detection scenarios. In this chapter, we review the state of the art in risk perception/communication research related to astrobiology and detection. Based on three major challenges (social risk amplification/attenuation, misguided risk information seeking, ineffective risk message design), we explore the contribution of risk communication theory (SARF, RISP, EPPM, IDEA) to future research and institutional preparedness for potential detections of extraterrestrial life.

As part of the mission of the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU-CPS) Policy Hub to consider national and international regulations about the usage and sustainability in outer space, we also included discussion specific to the rights of Indigenous peoples with respect to outer space under the context of the United Nations Declaration for the Rights of Indigenous Peoples (UNDRIP). In this work, we review how some of the articles of UNDRIP require various actors in the use and exploitation of outer space including satellite companies, nation states, and professional/academic astronomy to consult and support Indigenous peoples/nations and respect Indigenous sovereignties. This work is concluded with recommendations for consulting and collaborating with Indigenous peoples and recommendations for moving from the traditional colonial exploitation of outer space and building an anti-colonial future in relationship with outer space.

We have searched for new members of the young Emilkowalski asteroid family. The number of family members reached 13. We determined proper synthetic orbital elements of family members using Orbit9 software. We investigated the dynamical evolution of the young Emilkowalski asteroid family over a 5 Myr with Orbit9 software. To estimate the ages of the pairs, we used the method of simultaneous convergence of the nodes and perihelion orbits. We considered all possible pairs between asteroids of the family. In the case of the zero-drift rate of the semi-major axis due to the influence of the Yarkovsky effect, the ages of the pairs do not exceed 2 Myr. The obtained estimates of the age of pairs allow us to limit the integration interval in the study of the probabilistic evolution of asteroid family orbits to the range of 2 Myr.

Our study addresses the challenges of direct exoplanet observation by introducing an innovative technique based on numerical simulations. We developed and evaluated a method combining Lyot coronagraphy with an Interferometric Apodization by Homothety (IAH) in segmented apertures, aimed at next-generation large telescopes. Simulations conducted using a wavelength range centered around 0.5 μm with a 20% bandwidth show significant improvements in contrast and reduced angular separations. The technique demonstrates low chromaticity, maintaining almost constant contrast across the wavelength range, an advantage over traditional methods. These findings represent a breakthrough in enhancing exoplanet imaging capabilities, enabling more precise detection even at low angular separations, and emphasize the critical role of numerical simulations in designing high dynamic range space imaging techniques.

We examine the phosphine on Venus debate using a multidimensional impact model covering scientific, social and psychological dimensions. We illustrate the results of the analysis with two spider diagrams.

This study analyzes the motion of bodies ejected from the Earth or the Moon. We studied the ejection of bodies from several points on the Earth’s surface, as well as from the most far point of the Moon from the Sun. Different velocities and angles of ejection of bodies were considered. The dynamical lifetimes of bodies reached a few hundred million years. Over the entire considered time interval, the values of the probability of a collision of a body ejected from the Earth with the Earth were approximately 0.3, 0.2, and 0.15–0.2 at an ejection velocity υej equaled to 11.5, 12, and 14 km/s, respectively. At υej≤11.3 km/s, most of the ejected bodies fell back onto the Earth. The total number of bodies delivered to the Earth and Venus probably did not differ much. The probabilities of collisions of bodies with Mercury and Mars usually did not exceed 0.1 and 0.02, respectively. At υej ≥11.5 km/s, the probability of a collision of a body ejected from the Earth with the Moon was about 15–35 times less than that with the Earth, and it was about 0.01. The probability of a collision with the Earth for a body ejected from the Moon moving in its present orbit was about 0.3–0.32, 0.2–0.22, and 0.1–0.14 at υej =2.5 km/s, υej =5 km/s, and at 12≤ υej ≤16.4 km/s, respectively.

Human civilization continues to experience rapid growth in energy consumption, while projections of population stabilization remain uncertain. A continued trajectory of exponential energy use would cause direct heating of the planet by ∼2300, which would also coincide with a transition to a Kardashev type-I civilization. If such patterns of energy consumption are typical for other technological civilizations, then the lack of evidence for extraterrestrial life suggests that Earth may be among the first. This implies that a “Great Filter” may exist in the near future, which would mark a critical juncture of whether civilization on Earth becomes spacefaring or extinct. Any extant technological civilizations are likely those that have achieved long-term equilibrium with energy consumption and population growth. The search for technosignatures by ongoing ground- and space-based observatories will provide a way to test the Great Filter hypothesis and examine the extent to which energy-intensive civilizations occur in the galaxy.

The Magellanic Stream (MS), a tail of diffuse gas formed from tidal and ram pressure interactions between the Small and Large Magellanic Clouds (SMC and LMC) and the Halo of the Milky Way, is primarily composed of neutral atomic hydrogen (HI). The deficiency of dust and the diffuse nature of the present gas make molecular formation rare and difficult, but if present, could lead to regions potentially suitable for star formation, thereby allowing us to probe conditions of star formation similar to those at high redshifts. We search for $\text{HCO}^{+}$, HCN, HNC, and C$_2$H using the highest sensitivity observations of molecular absorption data from the Atacama Large Millimeter Array (ALMA) to trace these regions, comparing with HI archival data from the Galactic Arecibo L-Band Feed Array (GALFA) HI Survey and the Galactic All Sky Survey (GASS) to compare these environments in the MS to the HI column density threshold for molecular formation in the Milky Way. We also compare the line of sight locations with confirmed locations of stars, molecular hydrogen, and OI detections, though at higher sensitivities than the observations presented here.

We find no detections to a 3$\sigma$ significance, despite four sightlines having column densities surpassing the threshold for molecular formation in the diffuse regions of the Milky Way. Here we present our calculations for the upper limits of the column densities of each of these molecular absorption lines, ranging from $3 \times 10^{10}$ to $1 \times 10^{13}$ cm$^{-2}$. The non-detection of $\text{HCO}^{+}$ suggests that at least one of the following is true: (i) $X_{\text{HCO}^{+}{}, \mathrm{MS}}$ is significantly lower than the Milky Way value; (ii) that the widespread diffuse molecular gas observed by Rybarczyk (2022b, ApJ, 928, 79) in the Milky Way’s diffuse interstellar medium (ISM) does not have a direct analogue in the MS; (iii) the HI-to-$\text{H}_{2}$ transition occurs in the MS at a higher surface density in the MS than in the LMC or SMC; or (iv) molecular gas exists in the MS, but only in small, dense clumps.

This paper presents the effects of radio frequency interference (RFI) mitigation on a radio telescope’s sensitivity and beam pattern. It specifically explores the impact of subspace-projection mitigation on the phased array feed (PAF) beams of the Australian SKA Pathfinder (ASKAP) telescope. The goal is to demonstrate ASKAP’s ability to make science observations during active RFI mitigation. The target interfering signal is a self-generated clock signal from the digital receivers of ASKAP’s PAF. This signal is stationary, so we apply the mitigation projection to the beamformer weights at the beginning of the observation and hold them fixed. We suppressed the unwanted narrowband signal by 31 dB, to the noise floor of an 880 s integration on one antenna, with a typical degradation in sensitivity of just 1.5%. Sensitivity degradation over the whole 36 antenna array of 3.1% was then measured via interferometric assessment of system equivalent flux density (SEFD). These measurements are in line with theoretical calculation of noise increase using the correlation of the beam weights and RFI spatial signature. Further, degradation to the main beam’s gain is $\pm$ 0.4% on average at the half-power point, with no significant change to the gain in the first sidelobe and no variation during extended observations; also consistent with our modelling. In summary, we present the first demonstration of mitigation via spatial nulling with PAFs on a large aperture synthesis array telescope and assess impact on sensitivity and beam shape via SEFD and holography measurements. The mitigation introduces smaller changes to sensitivity than intrinsic sensitivity differences between beams, does not preclude high dynamic range imaging and, in continuum 1 MHz mode, recovers an otherwise corrupted holography beam map and usable astronomical source correlations in the RFI-affected channel.

Trends in elemental enrichment with stellar age can give us a powerful avenue to identify thus far unexplained origin sites of the elements. We investigate stellar abundance trends using the GALAH DR3 high-resolution spectroscopic dataset of 6 234 solar-type stars. Our study explores the elemental abundance [X/Fe] of sodium (Na) with stellar age. We find a pronounced enrichment in [Na/Fe] at super solar metallicity (i.e. [Fe/H] $ \gt \,0$) in the old sequence of Milky Way disc stars, a trend demanding a deeper understanding of the underlying source(s) responsible for the nucleosynthesis. This progressive [Na/Fe] enrichment at the young end of the old sequence has essential implications for Galactic archaeology. In this work, we propose a novel selection technique for separating the Milky Way’s thick and thin disc stellar populations (i.e. old and young sequences) based on the observed [Na/Fe] rise of $\sim$0.1 dex for stars around 5–8 Gyr old. We also compare our selection method to the conventional [Mg/Fe] vs. [Fe/H] selection approach, and we find that our new Na-based selection method better disentangles the overlap between young- and old-sequence disc stars at these intermediate ages. This is especially true at super solar [Fe/H], where the [Mg/Fe] vs. [Fe/H] or [$\alpha$/Fe] vs. [Fe/H] separation approaches exhibit significant overlap. This new selection method should help us better understand the history of the formation of the Milky Way disc.

Results from some recent numerical works, including ours, lend credence to the thesis that the ambient environment, that is, the magnitude of external pressure, affects the star-forming ability of clouds and filaments. In continuation with our series of papers on this subject, we explore this thesis further by developing new hydrodynamic simulations of accreting filaments confined by external pressures in the range $10^{4 -7}$ K cm$^{-3}$. Our principal findings are – (i) irrespective of linemass, filament-fragmentation generally yields spheroidal cores. The initially sub-critical filaments in low to intermediate external pressure environments form broad cores suggesting that weakly self-gravitating filaments must fragment via the collect – and- collapse mode to form broad cores. Transcritical filaments, by contrast, become susceptible to the Jeans-type instability and form pinched cores; (ii) the ambient environment bears upon the physical properties of filaments including their FWHM$_{fil}$. Only the filaments initially suffused with subsonic turbulence in Solar-Neighbourhood-like environments, however, have FWHM$_{fil}$$\sim$ 0.1 pc. In high pressure environs such filaments not only have much smaller widths, but also become severely eviscerated. On the contrary, filaments suffused with initially supersonic turbulence are typically broader; (iii) the quasi-oscillatory nature of velocity gradients must be ubiquitous along filament lengths and its magnitude generally increases with increasing pressure. The periodicity of the velocity gradients approximately matches the fragmentation lengthscale of filaments; (iv) oscillatory features of the radial component of the velocity gradient are a unreliable proxy for detecting signatures of accretion onto filaments; and (v) filaments at either extreme of external pressure are inefficient at cycling gas into the dense phase which could reconcile the corresponding inefficiency of star-formation in such environments.

Fast radio bursts (FRBs) are millisecond-duration radio waves from the Universe. Even though more than 50 physical models have been proposed, the origin and physical mechanism of FRB emissions are still unknown. The classification of FRBs is one of the primary approaches to understanding their mechanisms, but previous studies classified conventionally using only a few observational parameters, such as fluence and duration, which might be incomplete. To overcome this problem, we use an unsupervised machine-learning model, the Uniform Manifold Approximation and Projection to handle seven parameters simultaneously, including amplitude, linear temporal drift, time duration, central frequency, bandwidth, scaled energy, and fluence. We test the method for homogeneous 977 sub-bursts of FRB 20121102A detected by the Arecibo telescope. Our machine-learning analysis identified five distinct clusters, suggesting the possible existence of multiple different physical mechanisms responsible for the observed FRBs from the FRB 20121102A source. The geometry of the emission region and the propagation effect of FRB signals could also make such distinct clusters. This research will be a benchmark for future FRB classifications when dedicated radio telescopes such as the square kilometer array or Bustling Universe Radio Survey Telescope in Taiwan discover more FRBs than before.

We present new Australia Telescope Compact Array (ATCA) radio observations towards N 49, one of the brightest extragalactic supernova remnants (SNRs) located in the Large Magellanic Cloud (LMC). Our new and archival ATCA radio observations were analysed along with Chandra X-ray data. These observations show a prominent ‘bullet’ shaped feature beyond the southwestern boundary of the SNR. Both X-ray morphology and radio polarisation analysis support a physical connection of this feature to the SNR. The ‘bullet’ feature’s apparent velocity is estimated at $\sim$1 300 km s$^{-1}$, based on its distance ($\sim$10 pc) from the remnant’s geometric centre and estimated age ($\sim$7 600 yr). we estimated the radio spectral index, $\alpha= -0.55 \pm 0.03$ which is typical of middle-age SNRs. Polarisation maps created for N 49 show low to moderate levels of mean fractional polarisation estimated at 7$\pm$1% and 10$\pm$1% for 5.5 and 9 GHz, respectively. These values are noticeably larger than found in previous studies. Moreover, the mean value for the Faraday rotation of SNR N 49 from combining CABB data is 212$\pm$65 rad m$^{-2}$ and the maximum value of RM is 591$\pm$103 rad m$^{-2}$.

We present the Pilot Survey Phase 2 data release for the Wide-field ASKAP L-band Legacy All-sky Blind surveY (WALLABY), carried-out using the Australian SKA Pathfinder (ASKAP). We present 1760 H i detections (with a default spatial resolution of 30′′) from three pilot fields including the NGC 5044 and NGC 4808 groups as well as the Vela field, covering a total of $\sim 180$ deg$^2$ of the sky and spanning a redshift up to $z \simeq 0.09$. This release also includes kinematic models for over 126 spatially resolved galaxies. The observed median rms noise in the image cubes is 1.7 mJy per 30′′ beam and 18.5 kHz channel. This corresponds to a 5$\sigma$ H i column density sensitivity of $\sim 9.1\times10^{19}(1 + z)^4$ cm$^{-2}$ per 30′′ beam and $\sim 20$ km s$^{-1}$ channel and a 5$\sigma$ H i mass sensitivity of $\sim 5.5\times10^8 (D/100$ Mpc)$^{2}$ M$_{\odot}$ for point sources. Furthermore, we also present for the first time 12′′ high-resolution images (“cut-outs”) and catalogues for a sub-sample of 80 sources from the Pilot Survey Phase 2 fields. While we are able to recover sources with lower signal-to-noise ratio compared to sources in the Public Data Release 1, we do note that some data quality issues still persist, notably, flux discrepancies that are linked to the impact of side lobes associated with the dirty beams due to inadequate deconvolution. However, in spite of these limitations, the WALLABY Pilot Survey Phase 2 has already produced roughly a third of the number of HIPASS sources, making this the largest spatially resolved H i sample from a single survey to date.