Pub Date : 2025-01-22DOI: 10.1016/j.newar.2024.101721
Jason A.S. Hunt, Eugene Vasiliev
The Gaia mission has triggered major developments in the field of Galactic dynamics in recent years, which we discuss in this review. The structure and kinematics of all Galactic components – disc, bar/bulge and halo – are now mapped in great detail not only in the Solar neighbourhood, but across a large part of the Milky Way. The dramatic improvements in the coverage and precision of observations revealed various disequilibrium processes, such as perturbations in the Galactic disc and the deformations of the outer halo, which are partly attributed to the interaction with satellite galaxies. The knowledge of the gravitational potential at all scales has also advanced considerably, but we are still far from having a consistent view on the key properties of the Galaxy, such as the bar pattern speed or the mass profile and shape of the dark halo. The complexity and interplay of several dynamical processes makes the interpretation of observational data challenging, and it is fair to say that more theoretical effort is needed to fully reap the fruit of the Gaia revolution.
{"title":"Milky Way dynamics in light of Gaia","authors":"Jason A.S. Hunt, Eugene Vasiliev","doi":"10.1016/j.newar.2024.101721","DOIUrl":"10.1016/j.newar.2024.101721","url":null,"abstract":"<div><div>The <em>Gaia</em> mission has triggered major developments in the field of Galactic dynamics in recent years, which we discuss in this review. The structure and kinematics of all Galactic components – disc, bar/bulge and halo – are now mapped in great detail not only in the Solar neighbourhood, but across a large part of the Milky Way. The dramatic improvements in the coverage and precision of observations revealed various disequilibrium processes, such as perturbations in the Galactic disc and the deformations of the outer halo, which are partly attributed to the interaction with satellite galaxies. The knowledge of the gravitational potential at all scales has also advanced considerably, but we are still far from having a consistent view on the key properties of the Galaxy, such as the bar pattern speed or the mass profile and shape of the dark halo. The complexity and interplay of several dynamical processes makes the interpretation of observational data challenging, and it is fair to say that more theoretical effort is needed to fully reap the fruit of the <em>Gaia</em> revolution.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"100 ","pages":"Article 101721"},"PeriodicalIF":11.7,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-15DOI: 10.1016/j.newar.2025.101722
Aidan Meador-Woodruff , Dragan Huterer
Big Bang Nucleosynthesis (BBN), the process of creation of lightest elements in the early universe, is a highly robust, precise, and ultimately successful theory that forms one of the three pillars of the standard hot-Big-Bang cosmological model. Existing theoretical treatments of BBN and the associated computer codes are accurate and flexible, but are typically highly technical and opaque, and not suitable for pedagogical understanding of the BBN. Here we present BBN-simple – a from-scratch numerical calculation of the lightest element abundances pitched at an advanced undergraduate or beginning graduate level. We review the physics of the early universe relevant for BBN, provide information about the reaction rates, and discuss computational-mathematics background that is essential in setting up a BBN calculation. We calculate the abundances of the principal nuclear species in a standard cosmological model, and find a reasonably good agreement with public precision-level BBN codes. A condensed version of this paper and associated snippets of computer code are given at http://www-personal.umich.edu/~aidanmw/.
{"title":"BBN-simple: How to bake a universe-sized cake","authors":"Aidan Meador-Woodruff , Dragan Huterer","doi":"10.1016/j.newar.2025.101722","DOIUrl":"10.1016/j.newar.2025.101722","url":null,"abstract":"<div><div>Big Bang Nucleosynthesis (BBN), the process of creation of lightest elements in the early universe, is a highly robust, precise, and ultimately successful theory that forms one of the three pillars of the standard hot-Big-Bang cosmological model. Existing theoretical treatments of BBN and the associated computer codes are accurate and flexible, but are typically highly technical and opaque, and not suitable for pedagogical understanding of the BBN. Here we present <span>BBN-simple</span> – a from-scratch numerical calculation of the lightest element abundances pitched at an advanced undergraduate or beginning graduate level. We review the physics of the early universe relevant for BBN, provide information about the reaction rates, and discuss computational-mathematics background that is essential in setting up a BBN calculation. We calculate the abundances of the principal nuclear species in a standard cosmological model, and find a reasonably good agreement with public precision-level BBN codes. A condensed version of this paper and associated snippets of computer code are given at <span><span>http://www-personal.umich.edu/~aidanmw/</span><svg><path></path></svg></span>.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"100 ","pages":"Article 101722"},"PeriodicalIF":11.7,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-11-29DOI: 10.1016/j.newar.2024.101714
Brahma Gopalchetty
Understanding the status of water on Mars is crucial for evaluating its capacity to support life and to serve as a resource for future possible human exploration. Investigations have been carried out in the past to find signs of water in its past or present states. It is generally agreed that Mars had significant amounts of water early in its existence, but today, only remnants exist, mostly as ice or within hydrous minerals. Current evidence of water on Mars includes geological features, Martian meteorites, sporadic wet flows on slopes, surface moisture detected by missions like Curiosity and Phoenix, and features suggesting ancient lakes and rivers. A notable recent discovery was an old streambed in Gale Crater, indicating the presence of considerable water flow in the past, which might have supported microbial life. Nowadays, Mars' arid surface is not suitable for life as we know it, leading scientists to focus on underground environments for the exploration of life and its respective biosignatures. Recent efforts have unveiled substantial underground ice reserves discovered by NASA in 2016 and a hidden subglacial lake identified by Italian researchers in 2018. The question of life on Mars still remains unresolved to date. This overview compiles the findings from diverse studies on Mars' water history and attempts to address the ongoing discussions about the potential for life on the planet.
{"title":"Martian hydrosphere: A brief overview of water on Mars","authors":"Brahma Gopalchetty","doi":"10.1016/j.newar.2024.101714","DOIUrl":"10.1016/j.newar.2024.101714","url":null,"abstract":"<div><div>Understanding the status of water on Mars is crucial for evaluating its capacity to support life and to serve as a resource for future possible human exploration. Investigations have been carried out in the past to find signs of water in its past or present states. It is generally agreed that Mars had significant amounts of water early in its existence, but today, only remnants exist, mostly as ice or within hydrous minerals. Current evidence of water on Mars includes geological features, Martian meteorites, sporadic wet flows on slopes, surface moisture detected by missions like Curiosity and Phoenix, and features suggesting ancient lakes and rivers. A notable recent discovery was an old streambed in Gale Crater, indicating the presence of considerable water flow in the past, which might have supported microbial life. Nowadays, Mars' arid surface is not suitable for life as we know it, leading scientists to focus on underground environments for the exploration of life and its respective biosignatures. Recent efforts have unveiled substantial underground ice reserves discovered by NASA in 2016 and a hidden subglacial lake identified by Italian researchers in 2018. The question of life on Mars still remains unresolved to date. This overview compiles the findings from diverse studies on Mars' water history and attempts to address the ongoing discussions about the potential for life on the planet.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"100 ","pages":"Article 101714"},"PeriodicalIF":11.7,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143146396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-11-28DOI: 10.1016/j.newar.2024.101713
Ana Bonaca , Adrian M. Price-Whelan
The hierarchical model of galaxy formation predicts that the Milky Way halo is populated by tidal debris of dwarf galaxies and globular clusters. Due to long dynamical times, debris from the lowest mass objects remains coherent as thin and dynamically cold stellar streams for billions of years. The Gaia mission, providing astrometry and spectrophotometry for billions of stars, has brought three fundamental changes to our view of cold stellar streams in the Milky Way. First, more than a hundred stellar streams have been discovered and characterized using Gaia data. This is an order of magnitude increase in the number of well-measured streams, thanks to Gaia’s capacity for identifying comoving groups of stars among the field Milky Way population. Second, Gaia data have revealed that density variations both along and across stellar streams are common. Dark-matter subhalos, as well as baryonic structures were theoretically predicted to form such features, but observational evidence for density variations was uncertain before Gaia. Third, stream kinematics are now widely available and have constrained the streams’ orbits and origins. Gaia has not only provided proper motions directly, but also enabled efficient spectroscopic follow-up of the proper-motion selected targets. These discoveries have established stellar streams as a dense web of sensitive gravitational tracers in the Milky Way halo. We expect the coming decade to bring a full mapping of the Galactic population of stellar streams, as well as develop numerical models that accurately explain their evolution within the Milky Way for a variety of cosmological models. Perhaps most excitingly, the comparison between the two will be able to reveal the presence of dark-matter subhalos below the threshold for galaxy formation (), and provide the most stringent test of the cold dark matter paradigm on small scales.
{"title":"Stellar streams in the Gaia era","authors":"Ana Bonaca , Adrian M. Price-Whelan","doi":"10.1016/j.newar.2024.101713","DOIUrl":"10.1016/j.newar.2024.101713","url":null,"abstract":"<div><div>The hierarchical model of galaxy formation predicts that the Milky Way halo is populated by tidal debris of dwarf galaxies and globular clusters. Due to long dynamical times, debris from the lowest mass objects remains coherent as thin and dynamically cold stellar streams for billions of years. The <em>Gaia</em> mission, providing astrometry and spectrophotometry for billions of stars, has brought three fundamental changes to our view of cold stellar streams in the Milky Way. First, more than a hundred stellar streams have been discovered and characterized using <em>Gaia</em> data. This is an order of magnitude increase in the number of well-measured streams, thanks to <em>Gaia</em>’s capacity for identifying comoving groups of stars among the field Milky Way population. Second, <em>Gaia</em> data have revealed that density variations both along and across stellar streams are common. Dark-matter subhalos, as well as baryonic structures were theoretically predicted to form such features, but observational evidence for density variations was uncertain before <em>Gaia</em>. Third, stream kinematics are now widely available and have constrained the streams’ orbits and origins. <em>Gaia</em> has not only provided proper motions directly, but also enabled efficient spectroscopic follow-up of the proper-motion selected targets. These discoveries have established stellar streams as a dense web of sensitive gravitational tracers in the Milky Way halo. We expect the coming decade to bring a full mapping of the Galactic population of stellar streams, as well as develop numerical models that accurately explain their evolution within the Milky Way for a variety of cosmological models. Perhaps most excitingly, the comparison between the two will be able to reveal the presence of dark-matter subhalos below the threshold for galaxy formation (<span><math><mrow><mo>≲</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup><mspace></mspace><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></mrow></math></span>), and provide the most stringent test of the cold dark matter paradigm on small scales.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"100 ","pages":"Article 101713"},"PeriodicalIF":11.7,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143146395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.newar.2024.101712
Giada Bargiacchi , Maria Giovanna Dainotti , Salvatore Capozziello
Several correlations among Gamma-Ray Bursts (GRBs) quantities, both in the prompt and afterglow emissions, have been established during the last decades, thus enabling the standardization of GRBs as cosmological probes. Since GRBs are observed up to redshift , they represent a valuable tool to fill in the gap of information on the Universe evolution between the farthest type Ia supernovae and the Cosmic Microwave Background Radiation and to shed new light on the current challenging cosmological tensions. Without claiming for completeness, here we describe the state of the art of GRB correlations, their theoretical interpretations, and their cosmological applications both as standalone probes and in combination with other probes. In this framework, we pinpoint the importance of correcting the correlations for selection biases and redshift evolution to derive intrinsic relations, the assets of combining probes at different scales, and the need for the employment of the appropriate cosmological likelihood to precisely constrain cosmological parameters. Furthermore, we emphasize the benefits of the cosmographic approach to avoid any cosmological assumptions and the valuable applications of machine learning techniques to reconstruct GRB light curves and predict unknown GRB redshifts. Finally, we stress the relevance of all these factors, along with future observations, to definitely boost the power of GRBs in cosmology.
在过去的几十年里，伽马射线暴（GRBs）的数量（包括瞬时发射和余辉发射）之间已经建立了一些相关性，从而使伽马射线暴作为宇宙学探测器得以标准化。由于对 GRBs 的观测可以达到红移 z∼9，因此它们是填补最远的 Ia 型超新星和宇宙微波背景辐射之间宇宙演化信息空白的重要工具，也是揭示当前具有挑战性的宇宙学矛盾的新线索。在此，我们不求完整，只描述 GRB 相关技术的现状、其理论解释及其作为独立探测器或与其他探测器结合的宇宙学应用。在这一框架中，我们指出了校正相关性的选择偏差和红移演化以得出内在关系的重要性，在不同尺度上结合探测的好处，以及利用适当的宇宙学可能性来精确约束宇宙学参数的必要性。此外，我们还强调了宇宙学方法在避免任何宇宙学假设方面的优势，以及机器学习技术在重建 GRB 光变曲线和预测未知 GRB 红移方面的宝贵应用。最后，我们强调了所有这些因素与未来观测的相关性，它们必将提高 GRB 在宇宙学中的作用。
{"title":"High-redshift cosmology by Gamma-Ray Bursts: An overview","authors":"Giada Bargiacchi , Maria Giovanna Dainotti , Salvatore Capozziello","doi":"10.1016/j.newar.2024.101712","DOIUrl":"10.1016/j.newar.2024.101712","url":null,"abstract":"<div><div>Several correlations among Gamma-Ray Bursts (GRBs) quantities, both in the prompt and afterglow emissions, have been established during the last decades, thus enabling the standardization of GRBs as cosmological probes. Since GRBs are observed up to redshift <span><math><mrow><mi>z</mi><mo>∼</mo><mn>9</mn></mrow></math></span>, they represent a valuable tool to fill in the gap of information on the Universe evolution between the farthest type Ia supernovae and the Cosmic Microwave Background Radiation and to shed new light on the current challenging cosmological tensions. Without claiming for completeness, here we describe the state of the art of GRB correlations, their theoretical interpretations, and their cosmological applications both as standalone probes and in combination with other probes. In this framework, we pinpoint the importance of correcting the correlations for selection biases and redshift evolution to derive intrinsic relations, the assets of combining probes at different scales, and the need for the employment of the appropriate cosmological likelihood to precisely constrain cosmological parameters. Furthermore, we emphasize the benefits of the cosmographic approach to avoid any cosmological assumptions and the valuable applications of machine learning techniques to reconstruct GRB light curves and predict unknown GRB redshifts. Finally, we stress the relevance of all these factors, along with future observations, to definitely boost the power of GRBs in cosmology.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"100 ","pages":"Article 101712"},"PeriodicalIF":11.7,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-31DOI: 10.1016/j.newar.2024.101711
Aina Palau , Nuria Huélamo , David Barrado , Michael M. Dunham , Chang Won Lee
Brown Dwarfs (BDs) are crucial objects in our understanding of both star and planet formation, as well as in our understanding of what mechanisms shape the lower end of the Initial Mass Function (IMF). However, since the discovery of the first BD in 1995, there is still an unconcluded debate about which is the dominant formation mechanism of these objects. For this, it is mandatory to study BDs in their earliest evolutionary stages (what we call pre- and proto-BDs), comparable to the ‘pre-stellar’ and ‘Class 0/I’ stages well characterized for the formation of low-mass stars. In this review, the recent efforts aimed at searching, identifying and characterizing pre- and proto-BD candidates in nearby star-forming regions are presented, and revised requirements for an object to be a promising proto-BD or pre-BD candidate are provided, based on a new, unexplored so far, relation between the internal luminosity and the accreted mass. By applying these requirements, a list of 68 promising proto-BD candidates is presented, along with a compilation of possible pre-BDs from the literature. In addition, updated correlations of protostellar properties such as mass infall rate or outflow momentum rate with bolometric luminosity are provided down to the low-mass BD regime, where no significant deviations are apparent. Furthermore, the number proto-BD candidates in different clouds of the Solar Neighborhood seem to follow the known relations of number of protostars with cloud properties. In addition, proto(star-to-BD) ratios for the different clouds are also explored, unveiling a particular underproduction of low-mass proto-BD candidates in Ophiuchus compared to Lupus and Taurus. Possible explanations for this behavior are discussed, including heating of the Ophiuchus cloud by the nearby OB stars. The overall results of this work, along with the possibility that the planetary-mass regime of the IMF is subtly shaped by stellar feedback, tend to favor a Jeans-fragmentation process and therefore a star-like formation scenario down to the planetary boundary, of , below which other mechanisms might be at work. Future observational constraints, such as those provided by upcoming facilities like the next-generation Very Large Array, or the use of isotope ratios based on James Webb Space Telescope data, will provide definite clues to disentangle the origin of BDs in the planetary-mass regime.
{"title":"Observations of pre- and proto-brown dwarfs in nearby clouds: Paving the way to further constraining theories of brown dwarf formation","authors":"Aina Palau , Nuria Huélamo , David Barrado , Michael M. Dunham , Chang Won Lee","doi":"10.1016/j.newar.2024.101711","DOIUrl":"10.1016/j.newar.2024.101711","url":null,"abstract":"<div><div>Brown Dwarfs (BDs) are crucial objects in our understanding of both star and planet formation, as well as in our understanding of what mechanisms shape the lower end of the Initial Mass Function (IMF). However, since the discovery of the first BD in 1995, there is still an unconcluded debate about which is the dominant formation mechanism of these objects. For this, it is mandatory to study BDs in their earliest evolutionary stages (what we call pre- and proto-BDs), comparable to the ‘pre-stellar’ and ‘Class 0/I’ stages well characterized for the formation of low-mass stars. In this review, the recent efforts aimed at searching, identifying and characterizing pre- and proto-BD candidates in nearby star-forming regions are presented, and revised requirements for an object to be a promising proto-BD or pre-BD candidate are provided, based on a new, unexplored so far, relation between the internal luminosity and the accreted mass. By applying these requirements, a list of 68 promising proto-BD candidates is presented, along with a compilation of possible pre-BDs from the literature. In addition, updated correlations of protostellar properties such as mass infall rate or outflow momentum rate with bolometric luminosity are provided down to the low-mass BD regime, where no significant deviations are apparent. Furthermore, the number proto-BD candidates in different clouds of the Solar Neighborhood seem to follow the known relations of number of protostars with cloud properties. In addition, proto(star-to-BD) ratios for the different clouds are also explored, unveiling a particular underproduction of low-mass proto-BD candidates in Ophiuchus compared to Lupus and Taurus. Possible explanations for this behavior are discussed, including heating of the Ophiuchus cloud by the nearby OB stars. The overall results of this work, along with the possibility that the planetary-mass regime of the IMF is subtly shaped by stellar feedback, tend to favor a Jeans-fragmentation process and therefore a star-like formation scenario down to the planetary boundary, of <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>01</mn></mrow></math></span> <span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>, below which other mechanisms might be at work. Future observational constraints, such as those provided by upcoming facilities like the next-generation Very Large Array, or the use of isotope ratios based on James Webb Space Telescope data, will provide definite clues to disentangle the origin of BDs in the planetary-mass regime.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101711"},"PeriodicalIF":11.7,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-03DOI: 10.1016/j.newar.2024.101710
Peiying He , Chunyu Ding
Although the Ku-band Cassini RADAR was not primarily designed to probe Titan’s subsurface structure, it unexpectedly provided valuable data on penetration, notably measuring the depth and dielectric properties of several lakes or seas in altimetry mode. While the RADAR did not possess the same penetration capability as the radar instruments that are used to search for water on Mars, its detection results and potential still warrant comprehensive integration and summary. This paper reviews the latest research findings on Titan’s subsurface observations, encompassing liquid bodies and dunes, grounded on RADAR’s penetration performance and principles. In consideration of the Dragonfly mission and its scientific goals, the paper reviews the distribution of water ice on Titan. The upcoming observations hold promise for investigating relevant features at low latitudes, such as impact craters with exposed ice-rich material. Finally, suggestions and prospects for future subsurface radar exploration of Titan are presented. The exploration of subsurface structures on Titan remains a captivating field of study, bearing significant implications for planetary science and astrobiology.
虽然卡西尼号 Ku 波段雷达的主要设计目的不是探测土卫六的地表下结构，但它意外地提供了有价值的穿透数据，特别是在测高模式下测量了几个湖泊或海洋的深度和介电性质。虽然雷达不具备与用于在火星上寻找水的雷达仪器相同的穿透能力，但其探测结果和潜力仍然值得全面整合和总结。本文以雷达的穿透性能和原理为基础，回顾了土卫六地表下观测的最新研究成果，包括液态体和沙丘。考虑到 "蜻蜓 "任务及其科学目标，本文回顾了土卫六上水冰的分布情况。即将进行的观测有望调查低纬度地区的相关特征，如富含冰物质的撞击坑。最后，介绍了对未来土卫六地表下雷达探测的建议和展望。对土卫六地表下结构的探索仍然是一个引人入胜的研究领域，对行星科学和天体生物学具有重大意义。
{"title":"Exploring Titan’s subsurface: Insights from Cassini RADAR and prospects for future investigations","authors":"Peiying He , Chunyu Ding","doi":"10.1016/j.newar.2024.101710","DOIUrl":"10.1016/j.newar.2024.101710","url":null,"abstract":"<div><div>Although the Ku-band Cassini RADAR was not primarily designed to probe Titan’s subsurface structure, it unexpectedly provided valuable data on penetration, notably measuring the depth and dielectric properties of several lakes or seas in altimetry mode. While the RADAR did not possess the same penetration capability as the radar instruments that are used to search for water on Mars, its detection results and potential still warrant comprehensive integration and summary. This paper reviews the latest research findings on Titan’s subsurface observations, encompassing liquid bodies and dunes, grounded on RADAR’s penetration performance and principles. In consideration of the Dragonfly mission and its scientific goals, the paper reviews the distribution of water ice on Titan. The upcoming observations hold promise for investigating relevant features at low latitudes, such as impact craters with exposed ice-rich material. Finally, suggestions and prospects for future subsurface radar exploration of Titan are presented. The exploration of subsurface structures on Titan remains a captivating field of study, bearing significant implications for planetary science and astrobiology.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101710"},"PeriodicalIF":11.7,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-08-17DOI: 10.1016/j.newar.2024.101708
Vladimir Lipunov, Sergey Svertilov, Vladislav Topolev
In this review we show that the space experiment with gamma-ray detector with sensitivity 2 orders of magnitude higher than existing ones will make it possible to discover up to a thousand neutron star mergers, even at those moments when gravitational wave (GW) antennas are not working. At the same time, synchronous detection of neutron stars mergers by gamma-ray and GW detectors will make it possible not only to study in detail the physical processes occurring at the time of the catastrophe, but also to determine the full gamma ray beam pattern, including the average jet divergence angle and the real energy of the explosion. A gamma detector that has the required sensitivity at a relatively low flight weight is proposed. The latter, in turn, will make it possible to clarify our ideas about the genesis of double relativistic stars in the Universe.
{"title":"Gamma-ray bursts at extremely small fluence","authors":"Vladimir Lipunov, Sergey Svertilov, Vladislav Topolev","doi":"10.1016/j.newar.2024.101708","DOIUrl":"10.1016/j.newar.2024.101708","url":null,"abstract":"<div><p>In this review we show that the space experiment with gamma-ray detector with sensitivity 2 orders of magnitude higher than existing ones will make it possible to discover up to a thousand neutron star mergers, even at those moments when gravitational wave (GW) antennas are not working. At the same time, synchronous detection of neutron stars mergers by gamma-ray and GW detectors will make it possible not only to study in detail the physical processes occurring at the time of the catastrophe, but also to determine the full gamma ray beam pattern, including the average jet divergence angle and the real energy of the explosion. A gamma detector that has the required sensitivity at a relatively low flight weight is proposed. The latter, in turn, will make it possible to clarify our ideas about the genesis of double relativistic stars in the Universe.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101708"},"PeriodicalIF":11.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-08-07DOI: 10.1016/j.newar.2024.101709
Shad Ali, Tong Liu
This paper reviews the work done on black hole interior volume, entropy, and evaporation. An insight into the basics for understanding the interior volume is presented. A general analogy to investigate the interior volume of a black hole, the associated quantum mode’s entropy, and the evolution relation between the interior and exterior entropy is explained. Using this analogy, we predicted the future of information stored in a BH, its radiation, and evaporation. The results are noted in tables 1 and 2. To apply this analogy in BH space–time, we investigated the interior volume, entropy, and evaluation relation for different types of BHs. Finally, we also investigated the nature of BH radiation and the probability of particle emission during the evaporation process.
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Third generation and future upgrades of current gravitational-wave detectors will present exquisite sensitivities which will allow to detect a plethora of gravitational wave signals. Hence, a new problem to be solved arises: the detection and parameter estimation of overlapped signals. The problem of separating and identifying two signals that overlap in time, space or frequency is something well known in other fields (e.g. medicine and telecommunication). Blind source separation techniques are all those methods that aim at separating two or more unknown signals. This article provides a methodological review of the most common blind source separation techniques and it analyses whether they can be successfully applied to overlapped gravitational wave signals or not, while comparing the limits and advantages of each method.
{"title":"Blind source separation in 3rd generation gravitational-wave detectors","authors":"Francesca Badaracco , Biswajit Banerjee , Marica Branchesi , Andrea Chincarini","doi":"10.1016/j.newar.2024.101707","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101707","url":null,"abstract":"<div><p>Third generation and future upgrades of current gravitational-wave detectors will present exquisite sensitivities which will allow to detect a plethora of gravitational wave signals. Hence, a new problem to be solved arises: the detection and parameter estimation of overlapped signals. The problem of separating and identifying two signals that overlap in time, space or frequency is something well known in other fields (e.g. medicine and telecommunication). Blind source separation techniques are all those methods that aim at separating two or more unknown signals. This article provides a methodological review of the most common blind source separation techniques and it analyses whether they can be successfully applied to overlapped gravitational wave signals or not, while comparing the limits and advantages of each method.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101707"},"PeriodicalIF":11.7,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141540239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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