New Astronomy Reviews最新文献

Dark sector, constituting about 95% of the Universe, remains the subject of numerous studies. There are lots of models dealing with the cause of the effects assigned to “dark matter” and “dark energy”. This brief review is devoted to the very recent theoretical advances in these areas: only to the advances achieved in the last few years. For example, in section devoted to particle dark matter we overview recent publications on sterile neutrinos, self-interacting dark matter, dibarions (hexaquarks), dark matter from primordial “bubbles”, primordial black holes as dark matter, axions escaping from neutron stars, and dark and usual matter interacting via the fifth dimension. We also overview the second flavor of hydrogen atoms: their existence was proven by analyzing atomic experiments and is also evidenced by the latest astrophysical observations of the 21 cm spectral line from the early Universe. While discussing non-particle models of the cause of dark matter effects, we refer to modified Newtonian dynamics and modifications of the strong equivalence principles. We also consider exotic compact objects, primordial black holes, and retardation effects. Finally, we review recent studies on the cause of “dark energy effects”. Specifically, we cover two disputes that arose in 2019 and 2020 on whether the observations of supernovas, previously interpreted as the proof of the existence of dark energy, could have alternative explanations. Besides, we note a study of 2021, where dark energy is substituted by a new hypothetical type of dark matter having a magnetic-type interaction. We also refer to the recent model of a system of nonrelativistic neutral gravitating particles providing an alternative explanation of the entire dynamics of the Universe expansion – without introducing dark energy or new gravitational degrees of freedom.

The numerous compact sources associated with neutron stars and white dwarfs discovered in recent decades are analyzed in terms of the Gravimagnetic Rotator model (GMR paradigm–Lipunov, 1987a, 1992). We offer the instrument for understanding of various observed features and evolutionary relationships of neutron stars and white dwarfs. We depict in a single diagram all objects from radio pulsars and dwarf novae to ultra luminous X-ray sources and a radio pulsating white dwarf. This diagram directly demonstrates the genetic link between different types of compact sources thereby making it possible to confirm and illustrate clearly the established evolutionary connections–such as that between bulge X-ray sources and millisecond pulsars. This approach allows us to understand the evolutionary status of Ultra Luminous X-ray sources. In addition, we propose an additional evolutionary branch of the formation of Magnetars. When our work was completed, an article by Kirsten et al.2021, was published, which reports the localization of FRB 20,200,120 in one of the globular clusters of the galaxy M81. This shows that the accretion-induced collapse scenario of the white dwarf (Lipunov and Postnov, 1985), considered in detail in this work, is a possible genealogical branch of Magnetar production.

ESA’s INTEGRAL space mission has achieved unique results for solar and terrestrial physics, although spacecraft operations nominally excluded the possibility to point at the Sun or the Earth. The Earth avoidance was, however, exceptionally relaxed for special occultation observations of the Cosmic X-ray Background (CXB), which on some occasions allowed the detection of strong X-ray auroral emission. In addition, the most intense solar flares can be bright enough to be detectable from outside the field of view of the main instruments. This article presents for the first time the auroral observations by INTEGRAL and reviews earlier studies of the most intense solar flares. We end by briefly summarising the studies of the Earth’s radiation belts, which can be considered as another topic of serendipitous science with INTEGRAL.

When astrophysical jets were discovered one hundred years ago, the field of numerical simulations did not yet exit. Since the arrival of programmable computers though, numerical simulations have increasingly become an indispensable tool for dealing with “tough nut” problems which involve complex dynamic and non-linear phenomena. Astrophysical jets are an ideal example of such a tough nut, where multi-scale plasma physics, radiative and non-thermal processes, turbulence and relativity combine to present a formidable challenge to researchers.

Highlighting major achievements obtained through numerical simulations concerning the validity and nature of the Blandford–Znajek mechanism, the launching, collimation, acceleration and stability of jets, their interaction with the surrounding plasma, jet-galaxy feedback mechanisms etc., we trace how the field developed from its first tentative steps into the age of “maturity”. We also give a brief and personal outlook on how the field may evolve in the foreseeable future.

The major revolution in modern astronomy recognizing the universe as teeming with exoplanets, the discovery of liquid water in solar moons, and the continuing focus on Mars exploration, all accelerate the re-evaluation of potential biomarkers for extraterrestrial life. Based on life on planet Earth which relies heavily on chiral molecules and especially on homochiral families, the detection of molecules with these structural properties appears in all road-maps as prime indicators of extraterrestrial life. This review analyzes the strengths, bounds and potential weaknesses of relying on chirality and on homochirality as biomarkers, along with recommendations of how to practically use it. Some of the main issues presented, discussed and answered include: what is the extent to which chirality can be expected to be a universal feature of life; is detection of chirality enough or do we need also to detect homochirality; how justified is it to view life on Earth as purely homochiral; what are the weaknesses of the need to invent an arbitrary label of handedness (needed to define homochirality) and what are the pitfalls that emerge from these weaknesses; what stands behind a detected specific value of enantiomeric excess and what affects its values as we consider old, extinct life, just emerging embryonic life, or extant but rare life; how can one quantify the degree of homochirality; and, what are relevant experimental approached for detecting chirality on-ground and from distance? Finally, a summary with a concise list of recommendations is provided, along with a brief outlook.

Novae and supernovae play a key role in many fields of Astrophysics and Cosmology. Despite their importance, an accurate description of which objects explode and why and how they explode is still lacking. One of the main characteristics of such explosions is that they are the main suppliers of newly synthesized chemical elements in the Galaxy. Since some of these isotopes are radioactive, it is possible to use the corresponding gamma-rays as a diagnostic tool of the explosion thanks to their independence on the thermal state of the debris. The drawback is the poor sensitivity of detectors in the MeV energy domain. As a consequence, the radioactive lines have only been detected in one core collapse supernova (SN 1987A), one Type Ia supernova (SN 2014J), and one supernova remnant (Cas A). Nevertheless these observations have provided and are providing important information about the explosion mechanisms. Unfortunately, novae are still eluding detection. These results emphasize the necessity to place as soon as possible a new instrument in orbit with enough sensitivity to noticeably enlarge the sample of detected events.