Annual Review of Astronomy and Astrophysics最新文献_第10页

The Properties of the Solar Corona and Its Connection to the Solar Wind 日冕的性质及其与太阳风的关系

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-11-01 DOI: 10.1146/annurev-astro-091918-104416

S. Cranmer, A. Winebarger

{"title":"The Properties of the Solar Corona and Its Connection to the Solar Wind","authors":"S. Cranmer, A. Winebarger","doi":"10.1146/annurev-astro-091918-104416","DOIUrl":"https://doi.org/10.1146/annurev-astro-091918-104416","url":null,"abstract":"The corona is a layer of hot plasma that surrounds the Sun, traces out its complex magnetic field, and ultimately expands into interplanetary space as the supersonic solar wind. Although much has been learned in recent decades from advances in observations, theory, and computer simulations, we still have not identified definitively the physical processes that heat the corona and accelerate the solar wind. In this review, we summarize these recent advances and speculate about what else is required to finally understand the fundamental physics of this complex system. Specifically: ▪ We discuss recent subarcsecond observations of the corona, some of which appear to provide evidence for tangled and braided magnetic fields and some of which do not. ▪ We review results from three-dimensional numerical simulations that, despite limitations in dynamic range, reliably contain sufficient heating to produce and maintain the corona. ▪ We provide a new tabulation of scaling relations for a number of proposed coronal heating theories that involve waves, turbulence, braiding, nanoflares, and helicity conservation. An understanding of these processes is important not only for improving our ability to forecast hazardous space-weather events but also for establishing a baseline of knowledge about a well-resolved star that is relevant to other astrophysical systems.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":" ","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-091918-104416","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45592192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 70

Angular Momentum Transport in Stellar Interiors 恒星内部的角动量传输

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-20 DOI: 10.1146/annurev-astro-091918-104359

C. Aerts, S. Mathis, T. Rogers

{"title":"Angular Momentum Transport in Stellar Interiors","authors":"C. Aerts, S. Mathis, T. Rogers","doi":"10.1146/annurev-astro-091918-104359","DOIUrl":"https://doi.org/10.1146/annurev-astro-091918-104359","url":null,"abstract":"Stars lose a significant amount of angular momentum between birth and death, implying that efficient processes transporting it from the core to the surface are active. Space asteroseismology delivered the interior rotation rates of more than a thousand low- and intermediate-mass stars, revealing the following: ▪ Single stars rotate nearly uniformly during the core-hydrogen and core-helium burning phases. ▪ Stellar cores spin up to a factor of 10 faster than the envelope during the red giant phase. ▪ The angular momentum of the helium-burning core of stars is in agreement with the angular momentum of white dwarfs. Observations reveal a strong decrease of core angular momentum when stars have a convective core. Current theory of angular momentum transport fails to explain this. We propose improving the theory with a data-driven approach, whereby angular momentum prescriptions derived frommultidimensional (magneto)hydrodynamical simulations and theoretical considerations are continuously tested against modern observations. The TESS and PLATO space missions have the potential to derive the interior rotation of large samples of stars, including high-mass and metal-poor stars in binaries and clusters. This will provide the powerful observational constraints needed to improve theory and simulations.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":" ","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-091918-104359","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49386413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 128

Related Articles for Volume 56 第56卷的相关文章

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/annurev-aa-56-related-articles

引用次数: 0

Atomic and Ionized Microstructures in the Diffuse Interstellar Medium 漫射星际介质中的原子和电离微观结构

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/annurev-astro-081817-051810

S. Stanimirović, E. Zweibel

{"title":"Atomic and Ionized Microstructures in the Diffuse Interstellar Medium","authors":"S. Stanimirović, E. Zweibel","doi":"10.1146/annurev-astro-081817-051810","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-051810","url":null,"abstract":"It has been known for half a century that the interstellar medium (ISM) of our Galaxy is structured on scales as small as a few hundred kilometers, more than 10 orders of magnitude smaller than typical ISM structures and energy input scales. In this review we focus on neutral and ionized structures on spatial scales of a few to ∼104 AU, which appear to be highly overpressured, as these have the most important role in the dynamics and energy balance of interstellar gas: the tiny scale atomic structures (TSASs) and extreme scattering events (ESEs) as the most overpressured example of the tiny scale ionized structures (TSISs). We review observational results and highlight key physical processes at AU scales. We present evidence for and against microstructures as part of a universal turbulent cascade and as discrete structures, and we review their association with supernova remnants, the Local Bubble, and bright stars. We suggest a number of observational and theoretical programs that could clarify the nature of AU structures. TSAS and TSIS probe spatial scales in the range of what is expected for turbulent dissipation scales and are therefore of key importance for constraining exotic and not-well-understood physical processes that have implications for many areas of astrophysics. The emerging picture is one in which a magnetized, turbulent cascade, driven hard by a local energy source and acting jointly with phenomena such as thermal instability, is the source of these microstructures.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":" ","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-051810","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41929711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 19

Introduction 介绍

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/annurev-aa-56-071318-100001

S. Faber, E. V. van Dishoeck

引用次数: 0

Extreme Adaptive Optics 极端自适应光学

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/ANNUREV-ASTRO-081817-052000

O. Guyon

{"title":"Extreme Adaptive Optics","authors":"O. Guyon","doi":"10.1146/ANNUREV-ASTRO-081817-052000","DOIUrl":"https://doi.org/10.1146/ANNUREV-ASTRO-081817-052000","url":null,"abstract":"Over the last two decades, several thousand exoplanets have been identified, and their study has become a high scientific priority. Direct imaging of nearby exoplanets and the circumstellar disks in which they form and evolve is challenging due to the high contrast ratio and small angular separation relative to the central star. Exoplanets are typically within 1 arcsec of, and between 4 and 10 orders of magnitude fainter than, the stars they orbit. To meet these challenges, ground-based telescopes must be equipped with extreme adaptive optics (ExAO) systems optimized to acquire high-contrast images of the immediate surrounding of nearby bright stars. Current ExAO systems have the sensitivity to image thermal emission from young massive planets in near-IR, while future systems deployed on Giant Segmented Mirror Telescopes will image starlight reflected by lower-mass rocky planets. Thanks to rapid progress in optical coronagraphy, wavefront control, and data analysis techniques, direct imaging and spectroscopic characterization of habitable exoplanets will be within reach of the next generation of large ground-based telescopes.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/ANNUREV-ASTRO-081817-052000","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41390503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 72

Multiconjugate Adaptive Optics for Astronomy 用于天文学的多共轭自适应光学

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/ANNUREV-ASTRO-091916-055320

F. Rigaut, B. Neichel

{"title":"Multiconjugate Adaptive Optics for Astronomy","authors":"F. Rigaut, B. Neichel","doi":"10.1146/ANNUREV-ASTRO-091916-055320","DOIUrl":"https://doi.org/10.1146/ANNUREV-ASTRO-091916-055320","url":null,"abstract":"Since the year 2000, adaptive optics (AO) has seen the emergence of a variety of new concepts addressing particular science needs; multiconjugate adaptive optics (MCAO) is one of them. By correcting the atmospheric turbulence in 3D using several wavefront sensors and a tomographic phase reconstruction approach, MCAO aims to provide uniform diffraction limited images in the near-infrared over fields of view larger than 1 arcmin2, i.e., 10 to 20 times larger in area than classical single conjugated AO. In this review, we give a brief reminder of the AO principles and limitations, and then focus on aspects particular to MCAO, such as tomography and specific MCAO error sources. We present examples and results from past or current systems: MAD (Multiconjugate Adaptive Optics Demonstrator) and GeMS (Gemini MCAO System) for nighttime astronomy and the AO system, at Big Bear for solar astronomy. We examine MCAO performance (Strehl ratio up to 40% in H band and full width at half maximum down to 52 mas in the case of MCAO), with a particular focus on photometric and astrometric accuracy, and conclude with considerations on the future of MCAO in the Extremely Large Telescope and post–HST era.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":" ","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/ANNUREV-ASTRO-091916-055320","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45068330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 42

Rubble Pile Asteroids 碎石堆小行星

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/annurev-astro-081817-052013

K. Walsh

引用次数: 99

Cosmology Paradigm Changes 宇宙学范式的改变

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-09-14 DOI: 10.1146/ANNUREV-ASTRO-081817-051748

J. Einasto

引用次数: 0

Dynamical Evolution of the Early Solar System 早期太阳系的动力演化

IF 33.3 1区物理与天体物理

Annual Review of Astronomy and Astrophysics Pub Date : 2018-07-17 DOI: 10.1146/annurev-astro-081817-052028

D. Nesvorný

{"title":"Dynamical Evolution of the Early Solar System","authors":"D. Nesvorný","doi":"10.1146/annurev-astro-081817-052028","DOIUrl":"https://doi.org/10.1146/annurev-astro-081817-052028","url":null,"abstract":"Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an astronomical unit, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instability can be constrained from its present architecture. Specifically, we review arguments suggesting that the Solar System may have originally contained a third ice giant on a resonant orbit between Saturn and Uranus. This hypothesized planet was presumably ejected into interstellar space during the instability. The Kuiper belt kernel and other dynamical structures in the trans-Neptunian region may provide evidence for the ejected planet. We favor the early version of the instability where Neptune migrated into the outer planetesimal disk within a few tens of millions of years after the dispersal of the protosolar nebula. If so, the planetary migration/instability was not the cause of the Late Heavy Bombardment. Mercury's orbit may have been excited during the instability.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":" ","pages":""},"PeriodicalIF":33.3,"publicationDate":"2018-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1146/annurev-astro-081817-052028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42542366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 156