Pub Date : 2025-08-22DOI: 10.1146/annurev-astro-121024-051405
Louis E. Strigari
The classic model of the Local Group (LG) is that of two dominant constituents, the Milky Way and M31, first separating and then detaching from the Hubble flow, leading to a nearly radial-approaching orbit. This simple model has been confronted by new measurements of the three-dimensional M31 kinematics, by cosmological simulations, and by theoretical understanding of the impact of massive substructures, such as the Large Magellanic Cloud. This article explores the consequences of new observations and theory on the determination of the mass and dynamics of the LG. ▪ The M31 tangential velocity measurement and contribution from the cosmological constant both increase the implied timing mass of the LG to be ∼5 × 1012 M⊙. ▪ Timing mass estimates for the LG tend to be greater than the sum of the Milky Way and M31 halo masses, and greater than independent LG mass estimators. ▪ Precision future kinematics have the potential to explore the origin of this difference and shed light on dark matter in the LG, the origin of its angular momentum, and possibly even local values of cosmological parameters.
{"title":"Timing Mass of the Local Group","authors":"Louis E. Strigari","doi":"10.1146/annurev-astro-121024-051405","DOIUrl":"https://doi.org/10.1146/annurev-astro-121024-051405","url":null,"abstract":"The classic model of the Local Group (LG) is that of two dominant constituents, the Milky Way and M31, first separating and then detaching from the Hubble flow, leading to a nearly radial-approaching orbit. This simple model has been confronted by new measurements of the three-dimensional M31 kinematics, by cosmological simulations, and by theoretical understanding of the impact of massive substructures, such as the Large Magellanic Cloud. This article explores the consequences of new observations and theory on the determination of the mass and dynamics of the LG. <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> The M31 tangential velocity measurement and contribution from the cosmological constant both increase the implied timing mass of the LG to be ∼5 × 10<jats:sup>12</jats:sup> M<jats:sub>⊙</jats:sub>. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Timing mass estimates for the LG tend to be greater than the sum of the Milky Way and M31 halo masses, and greater than independent LG mass estimators. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Precision future kinematics have the potential to explore the origin of this difference and shed light on dark matter in the LG, the origin of its angular momentum, and possibly even local values of cosmological parameters. </jats:list-item> </jats:list>","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"51 1","pages":"431-466"},"PeriodicalIF":33.3,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144900288","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}
Pub Date : 2025-06-23DOI: 10.1146/annurev-astro-071221-052844
Erin Kara, Javier García
X-rays are a critical wavelength for understanding supermassive black holes (SMBHs). X-rays probe the inner accretion flow, closest to the event horizon, where gas inspirals, releasing energy and driving black hole growth. This region also governs the launching of outflows and jets that regulate galaxy evolution and link SMBH growth to their host galaxies. This review focuses on X-ray observations of SMBHs, through “standard accretion” in persistent active galactic nuclei (AGN) and in extreme transient events, such as tidal disruption events (TDEs), changing-look AGN, and quasi-periodic eruptions (QPEs). We describe the X-ray spectral and variability properties of AGN and the observational techniques that probe the inner accretion flow. By understanding the phenomenology and accretion physics in standard, individual AGN, we can better probe more exotic phenomena, including binary SMBH mergers or extreme mass ratio inspirals (EMRIs). In this review, the reader will discover the following:▪ X-ray variability on timescales from minutes to hours traces accretion near the event horizon. ▪ X-ray can measure the black hole mass, spin, and accretion flow geometry and dynamics. ▪ In transients like TDEs, X-rays probe the newly formed accretion disk that feeds the black hole. ▪ QPEs are posited to be EMRIs orbiting accreting SMBHs that would emit low-frequency gravitational waves. ▪ Future X-ray, time-domain, and multimessenger surveys will revolutionize our understanding of SMBH growth.
{"title":"Supermassive Black Holes in X-Rays: From Standard Accretion to Extreme Transients","authors":"Erin Kara, Javier García","doi":"10.1146/annurev-astro-071221-052844","DOIUrl":"https://doi.org/10.1146/annurev-astro-071221-052844","url":null,"abstract":"X-rays are a critical wavelength for understanding supermassive black holes (SMBHs). X-rays probe the inner accretion flow, closest to the event horizon, where gas inspirals, releasing energy and driving black hole growth. This region also governs the launching of outflows and jets that regulate galaxy evolution and link SMBH growth to their host galaxies. This review focuses on X-ray observations of SMBHs, through “standard accretion” in persistent active galactic nuclei (AGN) and in extreme transient events, such as tidal disruption events (TDEs), changing-look AGN, and quasi-periodic eruptions (QPEs). We describe the X-ray spectral and variability properties of AGN and the observational techniques that probe the inner accretion flow. By understanding the phenomenology and accretion physics in standard, individual AGN, we can better probe more exotic phenomena, including binary SMBH mergers or extreme mass ratio inspirals (EMRIs). In this review, the reader will discover the following:<jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> X-ray variability on timescales from minutes to hours traces accretion near the event horizon. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> X-ray can measure the black hole mass, spin, and accretion flow geometry and dynamics. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> In transients like TDEs, X-rays probe the newly formed accretion disk that feeds the black hole. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> QPEs are posited to be EMRIs orbiting accreting SMBHs that would emit low-frequency gravitational waves. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Future X-ray, time-domain, and multimessenger surveys will revolutionize our understanding of SMBH growth. </jats:list-item> </jats:list>","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"19 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144370696","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}
Pub Date : 2025-05-30DOI: 10.1146/annurev-astro-021225-030604
A.A. Vidotto
There are several physical processes that mediate the interaction between an exoplanet and its host star, with the four main ones being due to magnetic, particle (stellar outflow), radiative, and tidal interactions. These interactions can be observed at different wavelengths, from X-ray to radio. Their strengths depend on the architecture of planetary systems, as well as the age and activity level of the host stars. In particular, exoplanets in close-in orbits and/or orbiting active host stars can experience strong physical interactions, some of which are negligible or absent in the present-day Solar System planets. Here, I present an overview of star–planet interactions (SPIs) through the lens of three-dimensional (3D) numerical models. The main conclusions are as follows: ▪ Models are fundamental to interpret and guide observations. The powerful combination of observations and models allows us to extract important physical parameters of the system, such as planetary magnetic fields, stellar wind properties, etc. ▪ The nonaxisymmetric forces of the interactions generate spatially asymmetric features (e.g., planetary material trailing the orbit, shock formation), thus requiring the use of 3D models. ▪ SPIs vary in different timescales (from hours to gigayears) that are related to both planetary (orbital motion, rotation) and stellar (flares, cycles, and long-term evolution) properties. Understanding these variations requires time-dependent models. I advocate that future 3D models should be informed by multiwavelength, (near-)simultaneous observations. The use of observations is twofold: some generate inputs for models (e.g., stellar magnetic field maps), whereas others are fitted by models (e.g., spectroscopic transits). This combination of observations and models provides a powerful tool to derive physical properties of the system that would otherwise remain unknown.
{"title":"Star–Planet Interactions: A Computational View","authors":"A.A. Vidotto","doi":"10.1146/annurev-astro-021225-030604","DOIUrl":"https://doi.org/10.1146/annurev-astro-021225-030604","url":null,"abstract":"There are several physical processes that mediate the interaction between an exoplanet and its host star, with the four main ones being due to magnetic, particle (stellar outflow), radiative, and tidal interactions. These interactions can be observed at different wavelengths, from X-ray to radio. Their strengths depend on the architecture of planetary systems, as well as the age and activity level of the host stars. In particular, exoplanets in close-in orbits and/or orbiting active host stars can experience strong physical interactions, some of which are negligible or absent in the present-day Solar System planets. Here, I present an overview of star–planet interactions (SPIs) through the lens of three-dimensional (3D) numerical models. The main conclusions are as follows: <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> Models are fundamental to interpret and guide observations. The powerful combination of observations and models allows us to extract important physical parameters of the system, such as planetary magnetic fields, stellar wind properties, etc. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> The nonaxisymmetric forces of the interactions generate spatially asymmetric features (e.g., planetary material trailing the orbit, shock formation), thus requiring the use of 3D models. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> SPIs vary in different timescales (from hours to gigayears) that are related to both planetary (orbital motion, rotation) and stellar (flares, cycles, and long-term evolution) properties. Understanding these variations requires time-dependent models. </jats:list-item> </jats:list> I advocate that future 3D models should be informed by multiwavelength, (near-)simultaneous observations. The use of observations is twofold: some generate inputs for models (e.g., stellar magnetic field maps), whereas others are fitted by models (e.g., spectroscopic transits). This combination of observations and models provides a powerful tool to derive physical properties of the system that would otherwise remain unknown.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144184116","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}
Pub Date : 2025-05-29DOI: 10.1146/annurev-astro-052622-025659
Glenn van de Ven, Jesús Falcón-Barroso, Mariya Lyubenova
In this review, we show how combining dynamical and stellar population models with integral field spectroscopic data of nearby galaxies enable uncovering their assembly history. ▪ We discuss the advantages and limitations of various dynamical modelling approaches, focusing on measuring the mass distributions of nearby galaxies, including central black holes and dark matter halos. ▪ We highlight the use of Schwarzschild's orbit-superposition method to robustly decompose galaxies into dynamically distinct components and derive their intrinsic properties. ▪ We cover the application of single stellar population models to interpret observations of unresolved stars in nearby galaxies. ▪ We outline how combining dynamical and stellar population models can reveal the fossil records of galaxy assembly, from the origin of inner galaxy structures, to the buildup of disks, to the recovery of past galaxy mergers. We close by demonstrating how these models of nearby galaxies provide a bridge between studies of resolved stars in the local Universe and high-redshift galaxy observations. Together with direct coupling to state-of-the-art cosmological simulations, extragalactic archaeology promises key insights into galaxy formation and evolution.
{"title":"Extragalactic Archaeology: The Assembly History of Galaxies from Dynamical and Stellar Population Models","authors":"Glenn van de Ven, Jesús Falcón-Barroso, Mariya Lyubenova","doi":"10.1146/annurev-astro-052622-025659","DOIUrl":"https://doi.org/10.1146/annurev-astro-052622-025659","url":null,"abstract":"In this review, we show how combining dynamical and stellar population models with integral field spectroscopic data of nearby galaxies enable uncovering their assembly history. <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> We discuss the advantages and limitations of various dynamical modelling approaches, focusing on measuring the mass distributions of nearby galaxies, including central black holes and dark matter halos. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> We highlight the use of Schwarzschild's orbit-superposition method to robustly decompose galaxies into dynamically distinct components and derive their intrinsic properties. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> We cover the application of single stellar population models to interpret observations of unresolved stars in nearby galaxies. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> We outline how combining dynamical and stellar population models can reveal the fossil records of galaxy assembly, from the origin of inner galaxy structures, to the buildup of disks, to the recovery of past galaxy mergers. </jats:list-item> </jats:list> We close by demonstrating how these models of nearby galaxies provide a bridge between studies of resolved stars in the local Universe and high-redshift galaxy observations. Together with direct coupling to state-of-the-art cosmological simulations, extragalactic archaeology promises key insights into galaxy formation and evolution.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"147 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144176516","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}
Pub Date : 2025-05-28DOI: 10.1146/annurev-astro-052722-094843
Masahiro Ikoma, Hiroshi Kobayashi
Gas giant planets, if present, are the most massive objects in a planetary system and play a pivotal role in shaping its overall architecture. The formation of these planets has constantly been a central issue in planetary science. Increasing evidence from spacecraft explorations of Jupiter and Saturn, as well as telescope observations of exoplanets, has provided new constraints on the formation process of gas giant planets. The classic challenge of explaining formation timescales remains a significant issue, while new constraints on planetary interiors have introduced additional complexities. Recent shifts away from the single-size planetesimal hypothesis, nevertheless, show promise in resolving these problems. Additionally, various discoveries regarding exoplanets have led to theoretical improvements, while the discovery of numerous super-Earths and sub-Neptunes has posed new challenges in understanding gas accretion. This review synthesizes the latest theoretical advancements, discussing resolved issues and emerging challenges in giant planet formation.
{"title":"Formation of Giant Planets","authors":"Masahiro Ikoma, Hiroshi Kobayashi","doi":"10.1146/annurev-astro-052722-094843","DOIUrl":"https://doi.org/10.1146/annurev-astro-052722-094843","url":null,"abstract":"Gas giant planets, if present, are the most massive objects in a planetary system and play a pivotal role in shaping its overall architecture. The formation of these planets has constantly been a central issue in planetary science. Increasing evidence from spacecraft explorations of Jupiter and Saturn, as well as telescope observations of exoplanets, has provided new constraints on the formation process of gas giant planets. The classic challenge of explaining formation timescales remains a significant issue, while new constraints on planetary interiors have introduced additional complexities. Recent shifts away from the single-size planetesimal hypothesis, nevertheless, show promise in resolving these problems. Additionally, various discoveries regarding exoplanets have led to theoretical improvements, while the discovery of numerous super-Earths and sub-Neptunes has posed new challenges in understanding gas accretion. This review synthesizes the latest theoretical advancements, discussing resolved issues and emerging challenges in giant planet formation.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144165272","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}
Pub Date : 2025-05-22DOI: 10.1146/annurev-astro-020325-115713
Lorenzo Sironi, Dmitri A. Uzdensky, Dimitrios Giannios
Magnetic reconnection—a fundamental plasma physics process, where magnetic field lines of opposite polarity annihilate—is invoked in astrophysical plasmas as a powerful mechanism of nonthermal particle acceleration, able to explain fast-evolving, bright high-energy flares. Near black holes and neutron stars, reconnection occurs in the relativistic regime, in which the mean magnetic energy per particle exceeds the rest mass energy. This review reports recent advances in our understanding of the kinetic physics of relativistic reconnection: ▪ Kinetic simulations have elucidated the physics of plasma heating and nonthermal particle acceleration in relativistic reconnection (RR). ▪ The physics of radiative RR, with its self-consistent interplay between photons and reconnection-accelerated particles—a peculiarity of luminous, high-energy astrophysical sources—is the new frontier of research. ▪ RR plays a key role in global models of high-energy sources, in terms of both global-scale layers as well as reconnection sites generated as a by-product of local magnetohydrodynamic instabilities. We summarize themes of active investigation and future directions, emphasizing the role of upcoming observational capabilities, laboratory experiments, and new computational tools.
{"title":"Relativistic Magnetic Reconnection in Astrophysical Plasmas: A Powerful Mechanism of Nonthermal Emission","authors":"Lorenzo Sironi, Dmitri A. Uzdensky, Dimitrios Giannios","doi":"10.1146/annurev-astro-020325-115713","DOIUrl":"https://doi.org/10.1146/annurev-astro-020325-115713","url":null,"abstract":"Magnetic reconnection—a fundamental plasma physics process, where magnetic field lines of opposite polarity annihilate—is invoked in astrophysical plasmas as a powerful mechanism of nonthermal particle acceleration, able to explain fast-evolving, bright high-energy flares. Near black holes and neutron stars, reconnection occurs in the relativistic regime, in which the mean magnetic energy per particle exceeds the rest mass energy. This review reports recent advances in our understanding of the kinetic physics of relativistic reconnection: <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> Kinetic simulations have elucidated the physics of plasma heating and nonthermal particle acceleration in relativistic reconnection (RR). </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> The physics of radiative RR, with its self-consistent interplay between photons and reconnection-accelerated particles—a peculiarity of luminous, high-energy astrophysical sources—is the new frontier of research. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> RR plays a key role in global models of high-energy sources, in terms of both global-scale layers as well as reconnection sites generated as a by-product of local magnetohydrodynamic instabilities. </jats:list-item> </jats:list> We summarize themes of active investigation and future directions, emphasizing the role of upcoming observational capabilities, laboratory experiments, and new computational tools.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144113678","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}
Pub Date : 2025-05-19DOI: 10.1146/annurev-astro-021225-022840
Matthew A. Kenworthy, Sebastiaan Y. Haffert
Imaging terrestrial exoplanets around nearby stars is a formidable technical challenge, requiring the development of coronagraphs to suppress the stellar halo of diffracted light at the location of the planet. In this review, we discuss the science requirements for high-contrast imaging, present an overview of diffraction theory and the Lyot coronagraph, and define the parameters used in our optimization. We discuss the working principles of coronagraphs both in the laboratory and on-sky with current high-contrast instruments, and we describe the required algorithms and processes necessary for terrestrial planet imaging with extremely large telescopes and proposed space telescope missions: ▪ Imaging terrestrial planets around nearby stars is possible with a combination of coronagraphs and active wavefront control using feedback from wavefront sensors. ▪ Ground-based 8–40 m class telescopes can target the habitable zone around nearby M-dwarf stars with contrasts of 10−7, and space telescopes can search around solar-type stars with contrasts of 10−10. ▪ Focal plane wavefront sensing, hybrid coronagraph designs, and multiple closed loops providing active correction are required to reach the highest sensitivities. ▪ Polarization effects need to be mitigated in order to reach 10−10 contrasts while keeping exoplanet yields as high as possible. ▪ Recent technological developments, including photonics and microwave kinetic inductance detectors, will be folded into high-contrast instruments.
{"title":"High-Contrast Coronagraphy","authors":"Matthew A. Kenworthy, Sebastiaan Y. Haffert","doi":"10.1146/annurev-astro-021225-022840","DOIUrl":"https://doi.org/10.1146/annurev-astro-021225-022840","url":null,"abstract":"Imaging terrestrial exoplanets around nearby stars is a formidable technical challenge, requiring the development of coronagraphs to suppress the stellar halo of diffracted light at the location of the planet. In this review, we discuss the science requirements for high-contrast imaging, present an overview of diffraction theory and the Lyot coronagraph, and define the parameters used in our optimization. We discuss the working principles of coronagraphs both in the laboratory and on-sky with current high-contrast instruments, and we describe the required algorithms and processes necessary for terrestrial planet imaging with extremely large telescopes and proposed space telescope missions: <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> Imaging terrestrial planets around nearby stars is possible with a combination of coronagraphs and active wavefront control using feedback from wavefront sensors. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Ground-based 8–40 m class telescopes can target the habitable zone around nearby M-dwarf stars with contrasts of 10<jats:sup>−7</jats:sup>, and space telescopes can search around solar-type stars with contrasts of 10<jats:sup>−10</jats:sup>. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Focal plane wavefront sensing, hybrid coronagraph designs, and multiple closed loops providing active correction are required to reach the highest sensitivities. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Polarization effects need to be mitigated in order to reach 10<jats:sup>−10</jats:sup> contrasts while keeping exoplanet yields as high as possible. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Recent technological developments, including photonics and microwave kinetic inductance detectors, will be folded into high-contrast instruments. </jats:list-item> </jats:list>","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"73 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144097300","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}
Pub Date : 2025-05-14DOI: 10.1146/annurev-astro-052622-031342
Ignas A.G. Snellen
High-resolution spectroscopy (HRS) has grown into one of the main techniques for characterizing the atmospheres of extrasolar planets. High spectral resolving power allows for the efficient removal of telluric and host-star contamination. Combined with the large collecting area of ground-based telescopes, it enables detailed studies of atmospheric species, temperature structure, atmospheric loss, and global winds and circulation patterns. In this review, the wide range of HRS observation and data analysis techniques are described and literature results discussed. Key findings include the following: ▪ The highest irradiated planets show a rich spectrum of atomic and ionic species, just like stars. ▪ Retrieval analyses of hot Jupiters and directly imaged super-Jupiters point to solar metallicities and chemistry, but observed samples are still heterogeneous and incomplete. ▪ There appears to be a clear dichotomy between hot Jupiters with and without atmospheric inversions, depending on their equilibrium temperature. ▪ Some highly irradiated planets exhibit enormous leading and/or trailing tails of helium gas, providing unique insights into planet evolution and atmospheric escape processes. ▪ Minor isotopes of carbon and oxygen are now being detected in gas giant planets and brown dwarfs with the interesting potential to shed light on formation pathways. A list of potential pitfalls is provided for those new to the field, and synergies with the James Webb Space Telescope are discussed. HRS has a great future ahead with the advent of the extremely large telescopes, promising to bring temperate rocky exoplanets into view with their increase in HRS detection speed of up to three orders of magnitude.
{"title":"Exoplanet Atmospheres at High Spectral Resolution","authors":"Ignas A.G. Snellen","doi":"10.1146/annurev-astro-052622-031342","DOIUrl":"https://doi.org/10.1146/annurev-astro-052622-031342","url":null,"abstract":"High-resolution spectroscopy (HRS) has grown into one of the main techniques for characterizing the atmospheres of extrasolar planets. High spectral resolving power allows for the efficient removal of telluric and host-star contamination. Combined with the large collecting area of ground-based telescopes, it enables detailed studies of atmospheric species, temperature structure, atmospheric loss, and global winds and circulation patterns. In this review, the wide range of HRS observation and data analysis techniques are described and literature results discussed. Key findings include the following: <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> The highest irradiated planets show a rich spectrum of atomic and ionic species, just like stars. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Retrieval analyses of hot Jupiters and directly imaged super-Jupiters point to solar metallicities and chemistry, but observed samples are still heterogeneous and incomplete. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> There appears to be a clear dichotomy between hot Jupiters with and without atmospheric inversions, depending on their equilibrium temperature. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Some highly irradiated planets exhibit enormous leading and/or trailing tails of helium gas, providing unique insights into planet evolution and atmospheric escape processes. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Minor isotopes of carbon and oxygen are now being detected in gas giant planets and brown dwarfs with the interesting potential to shed light on formation pathways. </jats:list-item> </jats:list> A list of potential pitfalls is provided for those new to the field, and synergies with the <jats:italic>James Webb Space Telescope</jats:italic> are discussed. HRS has a great future ahead with the advent of the extremely large telescopes, promising to bring temperate rocky exoplanets into view with their increase in HRS detection speed of up to three orders of magnitude.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"42 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143979339","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}
Pub Date : 2025-04-01DOI: 10.1146/annurev-astro-013125-122023
H. Beuther, R. Kuiper, M. Tafalla
Star formation has often been studied by separating the low- and high-mass regimes with an approximate boundary at 8 M⊙. Although some of the outcomes of the star-formation process are different between the two regimes, it is less clear whether the physical processes leading to these outcomes are that different at all. Here, we systematically compare low- and high-mass star formation by reviewing the most important processes and quantities from an observational and theoretical point of view. We identify three regimes in which processes are either similar, quantitatively, or qualitatively different between low- and high-mass star formation. ▪ Similar characteristics can be identified for the turbulent gas properties and density structures of the star-forming regions. Many of the observational characteristics also do not depend that strongly on the environment. ▪ Quantitative differences can be found for outflow, infall, and accretion rates as well as mean column and volume densities. Also, the multiplicity significantly rises from low- to high-mass stars. The importance of the magnetic field for the formation processes appears still less well constrained. ▪ Qualitative differences between low- and high-mass star formation relate mainly to the radiative and ionizing feedback that occurs almost exclusively in regions forming high-mass stars. Nevertheless, accretion apparently can continue via disk structures in ionized accretion flows. Finally, we discuss to what extent a unified picture of star formation over all masses is possible and which issues need to be addressed in the future.
{"title":"Star Formation from Low to High Mass: A Comparative View","authors":"H. Beuther, R. Kuiper, M. Tafalla","doi":"10.1146/annurev-astro-013125-122023","DOIUrl":"https://doi.org/10.1146/annurev-astro-013125-122023","url":null,"abstract":"Star formation has often been studied by separating the low- and high-mass regimes with an approximate boundary at 8 M<jats:sub>⊙</jats:sub>. Although some of the outcomes of the star-formation process are different between the two regimes, it is less clear whether the physical processes leading to these outcomes are that different at all. Here, we systematically compare low- and high-mass star formation by reviewing the most important processes and quantities from an observational and theoretical point of view. We identify three regimes in which processes are either similar, quantitatively, or qualitatively different between low- and high-mass star formation. <jats:list list-type=\"bullet\"> <jats:list-item> <jats:label>▪</jats:label> Similar characteristics can be identified for the turbulent gas properties and density structures of the star-forming regions. Many of the observational characteristics also do not depend that strongly on the environment. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Quantitative differences can be found for outflow, infall, and accretion rates as well as mean column and volume densities. Also, the multiplicity significantly rises from low- to high-mass stars. The importance of the magnetic field for the formation processes appears still less well constrained. </jats:list-item> <jats:list-item> <jats:label>▪</jats:label> Qualitative differences between low- and high-mass star formation relate mainly to the radiative and ionizing feedback that occurs almost exclusively in regions forming high-mass stars. Nevertheless, accretion apparently can continue via disk structures in ionized accretion flows. </jats:list-item> </jats:list> Finally, we discuss to what extent a unified picture of star formation over all masses is possible and which issues need to be addressed in the future.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143775385","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}
Pub Date : 2024-09-13DOI: 10.1146/annurev-astro-071221-053007
Johanna K. Teske
The mantra “know thy star, know thy planet” has proven to be very important for many aspects of exoplanet science. Here I review how stellar abundances inform our understanding of planet composition and, thus, formation and evolution. In particular, I discuss how: ▪ The strongest star–planet connection is still the giant planet–metallicity correlation, the strength of which may indicate a break point between the formation of planets versus brown dwarfs. ▪ We do not have very good constraints on the lower metallicity limit for planet formation, although new statistics from TESS are helping, and it appears that, at low [Fe/H], α elements can substitute for iron as seeds for planet formation. ▪ The depletion of refractory versus volatile elements in stellar photospheres (particularly the Sun) was initially suggested as a sign of small planet formation but is challenging to interpret, and small differences in binary star compositions can be attributed mostly to processes other than planet formation. ▪ We can and should go beyond comparisons of the carbon-to-oxygen ratio in giant planets and their host stars, incorporating other volatile and refractory species to better constrain planet formation pathways. ▪ There appears to be a positive correlation between small planet bulk density and host star metallicity, but exactly how closely small planet refractory compositions match those of their host stars—and their true diversity—is still uncertain.
{"title":"The Star–Planet Composition Connection","authors":"Johanna K. Teske","doi":"10.1146/annurev-astro-071221-053007","DOIUrl":"https://doi.org/10.1146/annurev-astro-071221-053007","url":null,"abstract":"The mantra “know thy star, know thy planet” has proven to be very important for many aspects of exoplanet science. Here I review how stellar abundances inform our understanding of planet composition and, thus, formation and evolution. In particular, I discuss how: ▪ The strongest star–planet connection is still the giant planet–metallicity correlation, the strength of which may indicate a break point between the formation of planets versus brown dwarfs. ▪ We do not have very good constraints on the lower metallicity limit for planet formation, although new statistics from TESS are helping, and it appears that, at low [Fe/H], α elements can substitute for iron as seeds for planet formation. ▪ The depletion of refractory versus volatile elements in stellar photospheres (particularly the Sun) was initially suggested as a sign of small planet formation but is challenging to interpret, and small differences in binary star compositions can be attributed mostly to processes other than planet formation. ▪ We can and should go beyond comparisons of the carbon-to-oxygen ratio in giant planets and their host stars, incorporating other volatile and refractory species to better constrain planet formation pathways. ▪ There appears to be a positive correlation between small planet bulk density and host star metallicity, but exactly how closely small planet refractory compositions match those of their host stars—and their true diversity—is still uncertain.","PeriodicalId":8138,"journal":{"name":"Annual Review of Astronomy and Astrophysics","volume":"63 1","pages":""},"PeriodicalIF":33.3,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142231550","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}
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