308 Results Found

Earth’s early history provides the only natural record for evaluating how planetary evolution can generate environments capable of initiating life. Here we review early Earth evolution through the lens of urability: the time-dependent capacity...

This paper considers the problem of constrained multi-objective non-linear optimization of planetary gearbox based on hybrid metaheuristic algorithm. Optimal design of planetary gear trains requires simultaneous minimization of multiple conflicting o...

We present a brief review of the formation and evolution of hydrogen-deficient central stars of planetary nebulae. We include a detailed description of the main observable features of both the central stars and their surrounding nebulae and review th...

The morphologies of planetary nebula have long been believed to be due to wind shaping processes in which a “fast wind” from the central star impacts a previously ejected envelope. It is assumed that asymmetries existing in the “slow wind” envelope w...

I argue that the high percentage of planetary nebulae (PNe) that are shaped by jets show that main sequence stars in binary systems can accrete mass at a high rate from an accretion disk and launch jets. Not only does this allow jets to shape PNe, bu...

The increase in discovered close binary central stars of planetary nebulae is leading to a sufficiently large sample to begin to make broader conclusions about the effect of close binary stars on common envelope evolution and planetary nebula formati...

We review the evolution of our understanding of the planetary nebulae phenomenon and their place in the scheme of stellar evolution. The historical steps leading to our current understanding of central star evolution and nebular formation are discuss...

The stellar winds of the central stars of planetary nebulae play an essential role in the shaping of planetary nebulae. In the interacting stellar winds model, the fast stellar wind injects energy and momentum, which are transferred to the nebular en...

Planetary nebulae (PNe) are the ejected gas and dust shells of evolved low- and intermediate-mass stars (LIMSs). We present an abundance comparison between PNe and their progenitors to reveal their similarities and differences since such a comparison...

We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with di...

Ongoing improvements in the sensitivity of sub-mm- and mm-range interferometers and single-dish radio telescopes allow for the increasingly detailed study of AGB and post-AGB objects in molecular species other than ${}^{12}\mathrm{CO}$ and ${}^{13}\mathrm{CO}$. With a new update in...

Mass wasting, as one of the most significant geomorphological processes, contributes immensely to planetary landscape evolution. The frequency and diversity of mass wasting features on any planetary body also put engineering constraints on its roboti...

The study of minor chemical species in terrestrial planets’ atmospheres can teach us about the chemistry, dynamics and evolution of the atmospheres through time. Phosphine or methane on terrestrial planets are potential biosignatures, such that...

V4334 Sgr (Sakurai’s object) is an enigmatic evolved star that underwent a very late thermal pulse a few years before its discovery in 1996. It ejected a new hydrogen-deficient nebula in the process. The source has been observed continuously si...

We present new high-dispersion optical spectra of the planetary nebula NGC 2371 obtained with the Manchester Echelle Spectrometer at the OAN-SPM 2.1 m telescope, complemented with 3D morpho-kinematic modelling using ShapeX. The data reveal that the p...

We present the first results from comprehensive, near-UV-to-near-IR Hubble Space Telescope Wide Field Camera 3 (WFC3) emission-line imaging studies of two young planetary nebulae (PNe), NGC 7027 and NGC 6302. These two objects represent key sources f...

We are living in the Anthropocene period, where human activity has become the dominant influence on climate and the environment. Addressing the question of how nature and societies will evolve in the Anthropocene is one of the grand challenges of our...

This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of WORKPLANS is to build up a network of planetary nebulae (PNe) experts to address the main open questions in the field of PNe research. The specific aims o...

Planetary Nebulae (PNe) that are physical members of Galactic open clusters are powerful probes that allow precise determination of their distance and crucially their initial mass on the main sequence. Here, we revisit the physical association of the...

Information transmission via communication between agents is ubiquitous on Earth, and is a vital facet of living systems. In this paper, we aim to quantify this rate of information transmission associated with Earth’s biosphere and technosphere...

Methanogens, or methanogenic archaea (MA), are among the most ancient and widely distributed microorganisms, characterized by a unique metabolism that generates methane (CH₄) as the terminal product of anaerobic respiration. Their ability to grow and...

Root systems, the hidden half of terrestrial plants, have been a fundamental geological agent since the late Early Paleozoic, with their evolution preserved in a rich but underutilized archive of soils and sediments. This review adopts a rhizolith-ce...

Martian meteorites are the only samples from Mars available for extensive studies in laboratories on Earth. Among the various unresolved science questions, the question of the Martian atmospheric composition, distribution, and evolution over geologic...

The Planetary Boundary Layer (PBL) remains a popular research topic, given its fundamental role in the exchange of energy between the surface and the atmosphere. Understanding the PBL’s mechanisms can improve weather forecasting, climate and ai...

Stellar evolution models serve as tools to derive stellar parameters from elemental and isotopic abundance ratios. For low-to-intermediate mass evolved stars, C/O, ¹²C/¹³C, and ¹⁷O/¹⁸O ratios are proxies of the initial mass, a largely unknown paramet...

We present a morphokinematic analysis based on high-resolution long-slit echelle spectroscopy of the [N ii]$\lambda 6583$ line and narrowband imaging. Position–velocity diagrams reveal asymmetric expansion and localized kinematic features. We der...

More luminous than classical novae, but less luminous than supernovae, lies the exotic stellar eruptions known as Intermediate luminosity optical transients (ILOTs). They are divided into a number of sub-groups depending on the erupting progenitor an...

Light, color, and radial velocity data (2007–2015) for HD 161796, V887 Her, and HD 331319, three oxygen-rich post-AGB stars, have thus far not provided direct support for the binary hypothesis to explain the shapes of planetary nebulae and severely c...

We present preliminary results of our study of a small sample of planetary nebulae in the Galactic Bulge for which high-angular resolution Hubble Space Telescope imaging is available. From this and from archival spectroscopy, we were able to calculat...

Planetary nebulae (PNe) were expected to be filled with hot pressurized gas driving their expansion. ROSAT hinted at the presence of diffuse X-ray emission from these hot bubbles and detected the first sources of hard X-ray emission from their centra...

The aim of this work is to examine distances to planetary nebulae (PNe) together with other properties that were derived from them, using the astrometry of Gaia Data Release 2 (DR2). We were able to identify 1571 objects classified as PNe, for which...

Here, we study three fundamental climatic phenomena: The seasonal lag, the diurnal lag, and the asymmetry of daily temperature variation. We write a nonlinear ODE based on an energy balance for surface temperature and humidity. The model focuses on s...

The search for life outside Earth has been a popular topic for a long time in the scientific literature, but it gained more possibilities with the discovery of planets around other stars besides our Sun. In this sense, similarly to what happens in ou...

We present some preliminary findings on the population of planetary nebula where central stars (CSPN) have been independently identified in the HASH catalogue. Many new discoveries and candidates have been found (416 at the time of this writing), add...

We investigate the question whether or not the orbitals of exoplanets follow the symmetry-governed sequence found by Barut from the dynamical group of the Kepler problem. In particular, we consider their star distances, periods, and velocities. Previ...

In the centers of some planetary nebulae are found close binary stars. The formation of those planetary nebulae was likely through a common envelope event, which transformed an initially-wide progenitor binary into the currently observed close binary...

High-quality X-ray observations of planetary nebulae (PNe) have demonstrated that the X-ray-emitting gas in their hot bubbles have temperatures in the small range $T_{\mathrm{X}}$ = (1 − 3) × 10${}^6$ K. However, according to theoretical expectations, adiabatically-sho...

The investigation of gaseous nebulae, emitting in forbidden lines, is often based extensively on diagnostic diagrams. The special physics of these lines often allows for disentangling with a few line ratios normally coupled thermodynamic parameters l...

Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observati...

Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previous...

The grand challenges of our time—climate change, biodiversity losses, and global non-communicable disease rates—underscore that humanity and the planet are in crisis. Planetary health provides a unifying concept wherein efforts toward rem...

Iron occupies a unique place across the history of matter, from its formation in stars to its roles in planets, living systems, and human technology. Its nuclear properties help explain the accumulation of iron-group nuclei during stellar nucleosynth...

It is now clear that a vast majority of intermediate-mass stars have stellar and/or sub-stellar companions, therefore it is no longer appropriate to consider planetary nebulae as a single-star phenomenon, although some single, isolated stars may well...

Close binary evolution is widely invoked to explain the formation of axisymmetric planetary nebulae after a brief common envelope phase. The evolution of the primary would be interrupted abruptly, its still quite massive envelope being fully ejected...

While there has been significant progress in our understanding of the origin and evolution of planetary nebulae in the last 50 years, there remain several unsolved problems. These include the true 3D morphological structure of the nebulae, origin of...

We present a mathematical model for the propagation of the shock waves that occur during planetary collisions. Such collisions are thought to occur during the formation of terrestrial planets, and they have the potential to erode the planet’s a...

The interplay between stellar multiplicity and protoplanetary discs represents a cornerstone of modern astrophysics, offering key insights into the processes behind planet formation. Protoplanetary discs act as cradles for planetary systems, yet thei...

We discuss the spectral distinctions between B[e] stars and compact planetary nebulae. The differentiation between proto-planetary nebulae, transition objects between the asymptotic giant branch and planetary nebulae, and reflection nebulae in binary...

Our understanding of the processes that are relevant to the formation and maintenance of habitable planetary systems is advancing at a rapid pace, both from observation and theory. The present review focuses on recent research that bears on this topi...

The tectonic evolution of the early Earth remains one of the most debated questions in Earth science. Geological observations and geodynamic modeling have greatly expanded the range of plausible tectonic regimes, including subduction-like processes,...