Howell, SB

Marziani, P

McIntosh, SW

Puzzarini, C

English

Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna

Editorial: Horizons in Astronomy andAstrophysicsScott W. McIntosh1*, Paola Marziani 2, Cristina Puzzarini 3 and Steve B. Howell 41National Center for Atmospheric Research, Boulder, CO, United States, 2National Institute for Astrophysics, AstronomicalObservatory of Padua, Padua, Italy, 3Department of Chemistry “Giacomo Ciamician”, University of Bologna, Bologna, Italy,4NASA Ames Research Center, Moffett Field, CA, United StatesKeywords: astrobiology, astrochemistry, interstellar medium, solar physics, exoplanetsEditorial on the Research TopicHorizons in Astronomy and AstrophysicsWe are delighted to present the inaugural “Horizons in Astronomy and Astrophysics” articlecollection. This collection showcases high-impact, authoritative and reader-friendly review articlescovering important topics at the forefront of Astronomy and Astrophysics.The contributing authors were nominated by the Chief Editors of the Journal in recognition oftheir prominence and influence in their respective fields. The cutting-edge work presented in thisarticle collection highlights the diversity of research performed across the entire breadth ofAstronomy and Astrophysics, and reflects on the latest advances in the theory, experiment andmethodology with applications to compelling problems.The contribution of Luigi Foschini “Some Notes About the Current Researches on the Physics ofRelativistic Jets” (Foschini) provides an effective critical review about one of the most long-standingmysteries in extra-galactic astrophysics: the origin of relativistic radio ejections from the nuclei ofgalaxies. There are still fundamental issues lingering since the early days of radio astronomy, evenafter the many stunning images produced by the very large array and to long base-interferometry inthe most advanced expressions (such as space-based interferometry and the Event HorizonTelescope). Several basic issues are tackled: among them, the interpretation of the fundamentalscaling laws of black hole accretion, actually defined on biased sample and unfit to express afundamental accretion disk connection; the breaking-down of the blazar sequence jet power vs.electron cooling; the intermittent nature of the jet; the possibility of lepto-hadronic models to explainthe jet acceleration and some multimessenger phenomena associated with blazars; the jet energydissipation, and others. The paper poses many challenging questions that are still actual and that arereminescent of the ones posed to eminent workers 10 years ago (Marziani et al., 2012). The horizonhas been broadened but perhaps not as much as we had wished for.The contribution of Barone and Puzzarini “Toward accurate formation routes of complex organicmolecules in the interstellar medium: the paradigmatic cases of acrylonitrile and cyanomethanimine”(Barone and Puzzarini) highlights new information about important reactive channels operative indifferent regions of the interstellar medium (ISM) and in the atmospheres of exoplanets. The ISM ischaracterized by extreme physical conditions: temperatures that are usually very low (10–200 K),densities that are so low that can be considered as a high vacuum on Earth, and ionizing radiationsuch as cosmic and UV rays (Yamamoto, 2017). Despite such a harsh environment, its chemistry isvery rich. Owing to radioastronomy, about 270 molecules have been detected so far (Endres et al.,2016), with more than one third of them belonging to the so-called “complex organic molecules”[i.e., molecules with more than 5 atoms and containing at least 1 C atom; Herbst and van Dishoeck(2009)]. As addressed in the contribution Barone and Puzzarini, chemical reactions in the ISM canoccur on the surface of interstellar dust grains or in the gas phase. In both cases, reactivity has severeEdited and reviewed by:Didier Fraix-Burnet,UMR5274 Institut de Planétologie etd’Astrophysique de Grenoble (IPAG),France*Correspondence:Scott W. McIntoshmscott@ucar.eduSpecialty section:This article was submitted toExtragalactic Astronomy,a section of the journalFrontiers in Astronomy and SpaceSciencesReceived: 23 May 2022Accepted: 30 May 2022Published: 22 June 2022Citation:McIntosh SW, Marziani P, Puzzarini Cand Howell SB (2022) Editorial:Horizons in Astronomyand Astrophysics.Front. Astron. Space Sci. 9:951370.doi: 10.3389/fspas.2022.951370Frontiers in Astronomy and Space Sciences | www.frontiersin.org June 2022 | Volume 9 | Article 9513701EDITORIALpublished: 22 June 2022doi: 10.3389/fspas.2022.951370constraints: the reaction should be exothermic, should start with abarrierless approach of the reactants and must proceed withmechanisms only involving submerged reaction barriers. As aconsequence, one of the reactants should be a very reactivespecies like radicals and ions. This behavior is explained bythe fact that reactants can only count on their own energy,they do not get any “help” from the environment. In Baroneand Puzzarini, focusing on reactions taking place in the gas phase,it is demonstrated that quantum-chemical calculations at thestate of the art are able to derive reactions mechanisms able toexplain the reactivity of the ISM. Accurate computations of thethermochemistry and kinetics provide useful information for therationalization of chemistry of the ISM.The contribution of Antolin and Froment “Multi-scalevariability of coronal loops set by thermal non-equilibriumand instability as a probe for coronal heating” (Antolin andFroment) explores properties of solar coronal loops asfundamental building blocks of the Sun’s enigmatically hotcorona. These dynamic coronal structures are shaped by themagnetic field that expands into the solar atmosphere where theycan be observed in extreme ultraviolet (EUV) and X-raywavelengths—indicating the million plus Kelvin temperatureof the emitting plasma. While the dissipation of magneticenergy to heat the plasma to millions of degrees is the likelyculprit, the mechanisms setting the mass and energy circulationin the solar atmosphere is still a matter of debate and raised by theauthors. They discuss that multi-dimensional numerical modelsindicate that the very concept of a coronal loop as an individualentity is ill-defined due to the expected stochasticity of the solaratmosphere driven by magneto-convection. Highlighting therecent discovery of ubiquitous long-period EUV pulsations,the observed coronal rain properties and their common link inbetween represent not only major observational constraints forcoronal heating theories but also major theoretical puzzles. Themechanisms of thermal non-equilibrium (TNE) and thermalinstability (TI) appear in concert to explain these multi-scalephenomena as evaporation-condensation cycles. Recentnumerical efforts clearly illustrate the specific but largeparameter space involved in the heating and cooling aspects,and the geometry of the loop affecting the onset and properties ofsuch cycles. Their review presents and discusses this newapproach to inferring coronal heating properties andunderstanding the mass and energy cycle based on the multi-scale intensity variability and cooling properties set by the TNE-TI scenario.The contribution of Tennyson and Yurchenko “High accuracymolecular line lists for studies of exoplanets and other hotatmospheres” (Tennyson and Yurchenko) explores the desireto characterize the atmospheres of extrasolar planets that havebeen discovered over the last 3 decades. This goal is limited by thelack of spectroscopic data on the atmospheric molecules otherspecies that are readily available from laboratory studies. Theauthors review the currently available molecule spectra for studiesof exoplanet atmospheres, and the atmospheres of astronomicalobjects hotter than the Earth such as brown dwarfs, cool stars andeven sunspots. They discuss the dependency of exoplanet transitspectra and opacities analysis which often require huge datasetscomprising billions of individual spectroscopic transitions, whilethe new high resolution Doppler spectroscopy techniques rely onthe use of smaller, but very accurate line lists. They conclude theircontribution with a discussion on resolving the competingdemands of completeness versus accuracy for line lists neededtop explore and advance the Frontier field.The contribution of Herbst and Garrod “Synthetic approachesto complex organic molecules (COMs) in the cold interstellarmedium” (Herbst and Garrod) highlights the observation andsynthesis of organic molecules in interstellar space—one of themost exciting and rapidly growing topics in astrochemistry. Theyfocus on the diverse suggestions made to explain the formation ofCOMs in the low-temperature ISM where the dominantmechanisms at such low temperatures are still a matter ofdispute—where both gas-phase and granular processes areoccurring on and in ice mantles. They discuss the diffusiveand nondiffusive Granular mechanisms where a granularexplanation is strengthened by experiments at 10 K thatindicate that the synthesis of large molecules on granular icemantles under space-like conditions is exceedingly efficient.Similarly, the bombardment of carbon-containing ice mantlesin the laboratory by cosmic rays can lead to organic species evenat low temperatures. Further, for processes on dust grains to becompetitive at low temperatures non-thermal desorptionmechanisms must be invoked to explain why the organicmolecules are detected in the gas phase. Herbst and Garrodhighlight that while much remains to be learned, a betterunderstanding of low-temperature organic syntheses in spacewill add both to understanding of unusual chemical processes andthe role of molecules in stellar evolution.These articles provide a sample of the excellent Frontierresearch activities across solar, stellar and the broaderastrophysics discipline. In a year of community exercises to setstrategic priorities, the concepts emerging in this series will factorinto those conversations. We hope that you enjoy the collection.AUTHOR CONTRIBUTIONSAll authors listed have made a substantial, direct and intellectualcontribution to the work, and approved it for publication.ACKNOWLEDGMENTSThe Editors wish to thank all the authors and reviewers of thepapers submitted to this research topic for their time, their carefulwork, and their patience. We gratefully acknowledge theassistance of the staff in the Editorial Office of Frontiers.Frontiers in Astronomy and Space Sciences | www.frontiersin.org June 2022 | Volume 9 | Article 9513702McIntosh et al. Editorial: Horizons in Astronomy and AstrophysicsREFERENCESEndres, C. P., Schlemmer, S., Schilke, P., Stutzki, J., and Müller, H. S. P. (2016). TheCologne Database for Molecular Spectroscopy, Cdms, in the Virtual AtomicandMolecular Data Centre, Vamdc. J. Mol. Spectrosc. 327, 95–104. doi:10.1016/j.jms.2016.03.005Herbst, E., and van Dishoeck, E. F. (2009). Complex Organic Interstellar Molecules.Annu. Rev. Astron. Astrophys. 47, 427–480. doi:10.1146/annurev-astro-082708-101654Marziani, P., Sulentic, J. W., and D’Onofrio, M. (2012). An Introduction to 50 Yearsof Research on Quasars. Berlin, Heidelberg: Springer, 1–10. doi:10.1007/978-3-642-27564-7_1S Yamamoto (Editor) (2017). Introduction to Astrochemistry (ChemicalEvolution from Interstellar Clouds to Star and Planet Formation)(Tokyo, Japan: Springer).Conflict of Interest: The authors declare that the research was conducted in theabsence of any commercial or financial relationships that could be construed as apotential conflict of interest.Publisher’s Note: All claims expressed in this article are solely those of the authorsand do not necessarily represent those of their affiliated organizations, or those ofthe publisher, the editors and the reviewers. Any product that may be evaluated inthis article, or claim that may be made by its manufacturer, is not guaranteed orendorsed by the publisher.Copyright © 2022McIntosh, Marziani, Puzzarini and Howell. This is an open-accessarticle distributed under the terms of the Creative Commons Attribution License (CCBY).The use, distribution or reproduction in other forums is permitted, provided the originalauthor(s) and the copyright owner(s) are credited and that the original publication in thisjournal is cited, in accordance with accepted academic practice. No use, distribution orreproduction is permitted which does not comply with these terms.Frontiers in Astronomy and Space Sciences | www.frontiersin.org June 2022 | Volume 9 | Article 9513703McIntosh et al. Editorial: Horizons in Astronomy and Astrophysics

Editorial: Horizons in Astronomy and Astrophysics

https://cris.unibo.it/bitstream/11585/906014/1/Editorial_Horizon-fspas-09-951370.pdf

Editorial: Horizons in Astronomy and Astrophysics

Abstract

Similar works

Full text

Available Versions

Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna