Pub Date : 2024-09-04DOI: 10.1038/s41550-024-02349-x
Susanne Pfalzner, Amith Govind, Simon Portegies Zwart
Unlike the Solar System planets, thousands of smaller bodies beyond Neptune orbit the Sun on eccentric (e > 0.1 and i > 3°) orbits. While migration of the giant planets during the early stages of Solar System evolution could have induced substantial scattering of trans-Neptunian objects (TNOs), this process cannot account for the small number of distant TNOs (rp > 60 au) outside the planets’ reach. The alternative scenario of the close flyby of another star can instead produce all these TNO features simultaneously, but the possible parameter space for such an encounter is vast. Here we compare observed TNO properties with thousands of flyby simulations to determine the specific properties of a flyby that reproduces all the different dynamical TNO populations, their locations and their relative abundances, and find that a $$0.{8}_{-0.1}^{+0.1},{M}_{odot }$$ star passing at a distance of rp = 110 ± 10 au, inclined by i = 70° $${,}_{-10}^{+5}$$ , gives a near-perfect match. This flyby also replicates the retrograde TNO population, which has proved difficult to explain. Such a flyby is reasonably frequent; at least 140 million solar-type stars in the Milky Way are likely to have experienced a similar one. In light of these results, we predict that the upcoming Vera Rubin telescope will reveal that distant and retrograde TNOs are relatively common. The rocky disk surrounding the young Sun may have experienced a close flyby of another star. Simulations show that a highly inclined flyby of a star slightly smaller than the Sun at 100 au almost perfectly reproduces the orbits of the numerous small objects beyond Neptune.
与太阳系行星不同，海王星以外的数千个较小天体以偏心（e > 0.1 和 i >3°）轨道绕太阳运行。虽然在太阳系演化的早期阶段，巨行星的迁移可能会引起大量的跨海王星天体（TNOs）的散落，但这一过程无法解释行星覆盖范围之外的少量遥远的 TNOs（rp > 60 au）。另一种情况是近距离飞越另一颗恒星，这种情况可以同时产生所有这些 TNO 特征，但是这种相遇的可能参数空间非常大。在这里，我们将观测到的 TNO 特性与数千次飞越模拟进行了比较，以确定能够再现所有不同动态 TNO 群体、它们的位置和相对丰度的飞越的具体特性，并发现一颗 (0.{8}_{-0.1}^{+0.1},{M}_{odot }) 恒星在 rp = 110 ± 10 au 的距离上通过，倾斜度为 i = 70°({,}_{-10}^{+5})，给出了一个近乎完美的匹配。这次飞越也复制了逆行的 TNO 星群，事实证明这很难解释。这种飞掠相当频繁；银河系中至少有 1.4 亿颗太阳型恒星可能经历过类似的飞掠。鉴于这些结果，我们预测即将到来的维拉-鲁宾望远镜将揭示遥远的逆行 TNOs 是相对常见的。
{"title":"Trajectory of the stellar flyby that shaped the outer Solar System","authors":"Susanne Pfalzner, Amith Govind, Simon Portegies Zwart","doi":"10.1038/s41550-024-02349-x","DOIUrl":"10.1038/s41550-024-02349-x","url":null,"abstract":"Unlike the Solar System planets, thousands of smaller bodies beyond Neptune orbit the Sun on eccentric (e > 0.1 and i > 3°) orbits. While migration of the giant planets during the early stages of Solar System evolution could have induced substantial scattering of trans-Neptunian objects (TNOs), this process cannot account for the small number of distant TNOs (rp > 60 au) outside the planets’ reach. The alternative scenario of the close flyby of another star can instead produce all these TNO features simultaneously, but the possible parameter space for such an encounter is vast. Here we compare observed TNO properties with thousands of flyby simulations to determine the specific properties of a flyby that reproduces all the different dynamical TNO populations, their locations and their relative abundances, and find that a $$0.{8}_{-0.1}^{+0.1},{M}_{odot }$$ star passing at a distance of rp = 110 ± 10 au, inclined by i = 70° $${,}_{-10}^{+5}$$ , gives a near-perfect match. This flyby also replicates the retrograde TNO population, which has proved difficult to explain. Such a flyby is reasonably frequent; at least 140 million solar-type stars in the Milky Way are likely to have experienced a similar one. In light of these results, we predict that the upcoming Vera Rubin telescope will reveal that distant and retrograde TNOs are relatively common. The rocky disk surrounding the young Sun may have experienced a close flyby of another star. Simulations show that a highly inclined flyby of a star slightly smaller than the Sun at 100 au almost perfectly reproduces the orbits of the numerous small objects beyond Neptune.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 11","pages":"1380-1386"},"PeriodicalIF":12.9,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41550-024-02349-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142130826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-09-02DOI: 10.1038/s41550-024-02321-9
Chuanpeng Hou, Jiansen He, Die Duan, Ziqi Wu, Yajie Chen, Daniel Verscharen, Alexis P. Rouillard, Huichao Li, Liping Yang, Stuart D. Bale
There is renewed interest in heliospheric physics following the recent exploration of the pristine solar wind by the Parker Solar Probe. Magnetic switchback structures are frequently observed in the inner heliosphere, but there are open questions about their origin. Many researchers are investigating the statistical properties of switchbacks and their relationships with wave modes, stream types and solar activity, but the sources of switchbacks remain elusive. Here we report that interplanetary switchbacks originate from magnetic reconnection on the Sun that occurs at chromospheric network boundaries and launch solar jet flows. We link in situ interplanetary measurements and remote-sensing solar observations to establish a connection between interplanetary switchbacks and their solar source region, featuring solar jets, chromospheric network boundaries and photospheric magnetic field evolution. Our findings suggest that joint observations of switchbacks and solar jets provide a better estimate of the contribution of magnetic reconnection to coronal heating and solar wind acceleration. Chuanpeng Hou and co-authors report their findings on the origin of interplanetary switchbacks in solar magnetic reconnection at chromospheric network boundaries. This link between in situ and remote-sensing solar observations is a major step towards understanding coronal heating and solar wind acceleration.
{"title":"The origin of interplanetary switchbacks in reconnection at chromospheric network boundaries","authors":"Chuanpeng Hou, Jiansen He, Die Duan, Ziqi Wu, Yajie Chen, Daniel Verscharen, Alexis P. Rouillard, Huichao Li, Liping Yang, Stuart D. Bale","doi":"10.1038/s41550-024-02321-9","DOIUrl":"10.1038/s41550-024-02321-9","url":null,"abstract":"There is renewed interest in heliospheric physics following the recent exploration of the pristine solar wind by the Parker Solar Probe. Magnetic switchback structures are frequently observed in the inner heliosphere, but there are open questions about their origin. Many researchers are investigating the statistical properties of switchbacks and their relationships with wave modes, stream types and solar activity, but the sources of switchbacks remain elusive. Here we report that interplanetary switchbacks originate from magnetic reconnection on the Sun that occurs at chromospheric network boundaries and launch solar jet flows. We link in situ interplanetary measurements and remote-sensing solar observations to establish a connection between interplanetary switchbacks and their solar source region, featuring solar jets, chromospheric network boundaries and photospheric magnetic field evolution. Our findings suggest that joint observations of switchbacks and solar jets provide a better estimate of the contribution of magnetic reconnection to coronal heating and solar wind acceleration. Chuanpeng Hou and co-authors report their findings on the origin of interplanetary switchbacks in solar magnetic reconnection at chromospheric network boundaries. This link between in situ and remote-sensing solar observations is a major step towards understanding coronal heating and solar wind acceleration.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 10","pages":"1246-1256"},"PeriodicalIF":12.9,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41550-024-02321-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142118099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-08-27DOI: 10.1038/s41550-024-02343-3
Le Wang, Jun Huang
Various landforms suggest the past presence of liquid water on the surface of Mars. The putative coastal landforms, outflow channels and the hemisphere-wide Vastitas Borealis Formation sediments indicate that the northern lowlands may have housed an ancient ocean. Challenges to this hypothesis are from topography analysis, mineral formation environment and climate modelling. Determining whether there was a northern ocean on Mars is crucial for understanding its climate history, geological processes and potential for ancient life, and for guiding future explorations. Recently, China’s Zhurong rover has identified marine sedimentary structures and multiple subsurface sedimentary layers. The unique in situ perspective of the Zhurong rover, along with previous orbital observations, provides strong support for an episodic northern ocean during the early Hesperian and early Amazonian (about 3.6–2.5 billion years ago). The ground truth from future sample-return missions, such as China’s Tianwen-3 or the Mars sample-return programmes by NASA, ESA and other agencies, will be required for a more unambiguous confirmation. This Perspective presents the evidence in favour of and against the existence of an ancient ocean covering the Martian northern plains (Vastitas Borealis), discussing in particular the contribution of the Chinese Zhurong rover observations in supporting the presence of an ocean and the key role of the upcoming sample return.
{"title":"Hypothesis of an ancient northern ocean on Mars and insights from the Zhurong rover","authors":"Le Wang, Jun Huang","doi":"10.1038/s41550-024-02343-3","DOIUrl":"10.1038/s41550-024-02343-3","url":null,"abstract":"Various landforms suggest the past presence of liquid water on the surface of Mars. The putative coastal landforms, outflow channels and the hemisphere-wide Vastitas Borealis Formation sediments indicate that the northern lowlands may have housed an ancient ocean. Challenges to this hypothesis are from topography analysis, mineral formation environment and climate modelling. Determining whether there was a northern ocean on Mars is crucial for understanding its climate history, geological processes and potential for ancient life, and for guiding future explorations. Recently, China’s Zhurong rover has identified marine sedimentary structures and multiple subsurface sedimentary layers. The unique in situ perspective of the Zhurong rover, along with previous orbital observations, provides strong support for an episodic northern ocean during the early Hesperian and early Amazonian (about 3.6–2.5 billion years ago). The ground truth from future sample-return missions, such as China’s Tianwen-3 or the Mars sample-return programmes by NASA, ESA and other agencies, will be required for a more unambiguous confirmation. This Perspective presents the evidence in favour of and against the existence of an ancient ocean covering the Martian northern plains (Vastitas Borealis), discussing in particular the contribution of the Chinese Zhurong rover observations in supporting the presence of an ocean and the key role of the upcoming sample return.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 10","pages":"1220-1229"},"PeriodicalIF":12.9,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084845","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 : 2024-08-26DOI: 10.1038/s41550-024-02346-0
Jürgen Knödlseder, Mickael Coriat, Philippe Garnier, Annie Hughes
Research infrastructures have been identified as an important source of greenhouse gas emissions of astronomical research. Based on a comprehensive inventory of 1,211 ground-based observatories and space missions, we assessed the evolution of the number of astronomical facilities and their carbon footprint from 1945 to 2022. We found that space missions dominate greenhouse gas emissions in astronomy, showing an important peak at the end of the 1960s, followed by a decrease that has turned again into a rise over the last decade. Extrapolating past trends, we predict that greenhouse gas emissions from astronomical facilities will experience no strong decline in the future, and may even rise substantially, unless research practices are changed. We demonstrate that a continuing growth in the number of operating astronomical facilities is not environmentally sustainable. These findings should motivate the astronomical community to reflect about the necessary evolutions that would put astronomical research on a sustainable path. A comprehensive inventory of the carbon footprints of 1,211 ground-based astronomical observatories and space missions over a period of 78 years is used to model the expected future annual carbon footprint from astronomical research infrastructures.
{"title":"Scenarios of future annual carbon footprints of astronomical research infrastructures","authors":"Jürgen Knödlseder, Mickael Coriat, Philippe Garnier, Annie Hughes","doi":"10.1038/s41550-024-02346-0","DOIUrl":"10.1038/s41550-024-02346-0","url":null,"abstract":"Research infrastructures have been identified as an important source of greenhouse gas emissions of astronomical research. Based on a comprehensive inventory of 1,211 ground-based observatories and space missions, we assessed the evolution of the number of astronomical facilities and their carbon footprint from 1945 to 2022. We found that space missions dominate greenhouse gas emissions in astronomy, showing an important peak at the end of the 1960s, followed by a decrease that has turned again into a rise over the last decade. Extrapolating past trends, we predict that greenhouse gas emissions from astronomical facilities will experience no strong decline in the future, and may even rise substantially, unless research practices are changed. We demonstrate that a continuing growth in the number of operating astronomical facilities is not environmentally sustainable. These findings should motivate the astronomical community to reflect about the necessary evolutions that would put astronomical research on a sustainable path. A comprehensive inventory of the carbon footprints of 1,211 ground-based astronomical observatories and space missions over a period of 78 years is used to model the expected future annual carbon footprint from astronomical research infrastructures.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 11","pages":"1478-1486"},"PeriodicalIF":12.9,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084892","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 : 2024-08-21DOI: 10.1038/s41550-024-02344-2
ChangHoon Hahn, Pablo Lemos, Liam Parker, Bruno Régaldo-Saint Blancard, Michael Eickenberg, Shirley Ho, Jiamin Hou, Elena Massara, Chirag Modi, Azadeh Moradinezhad Dizgah, David Spergel
The standard ΛCDM cosmological model predicts the presence of cold dark matter, with the current accelerated expansion of the Universe driven by dark energy. This model has recently come under scrutiny because of tensions in measurements of the expansion and growth histories of the Universe, parameterized using H0 and S8. The three-dimensional clustering of galaxies encodes key cosmological information that addresses these tensions. Here we present a set of cosmological constraints using simulation-based inference that exploits additional non-Gaussian information on nonlinear scales from galaxy clustering, inaccessible with current analyses. We analyse a subset of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxy survey using SimBIG, a new framework for cosmological inference that leverages high-fidelity simulations and deep generative models. We use two clustering statistics beyond the standard power spectrum: the bispectrum and a summary of the galaxy field based on a convolutional neural network. We constrain H0 and S8 1.5 and 1.9 times more tightly than power spectrum analyses. With this increased precision, our constraints are competitive with those of other cosmological probes, even with only 10% of the full BOSS volume. Future work extending SimBIG to upcoming spectroscopic galaxy surveys (DESI, PFS, Euclid) will produce improved cosmological constraints that will develop understanding of cosmic tensions. By extracting non-Gaussian cosmological information on galaxy clustering at nonlinear scales, a framework for cosmic inference (SimBIG) provides more precise constraints for testing cosmological models.
{"title":"Cosmological constraints from non-Gaussian and nonlinear galaxy clustering using the SimBIG inference framework","authors":"ChangHoon Hahn, Pablo Lemos, Liam Parker, Bruno Régaldo-Saint Blancard, Michael Eickenberg, Shirley Ho, Jiamin Hou, Elena Massara, Chirag Modi, Azadeh Moradinezhad Dizgah, David Spergel","doi":"10.1038/s41550-024-02344-2","DOIUrl":"10.1038/s41550-024-02344-2","url":null,"abstract":"The standard ΛCDM cosmological model predicts the presence of cold dark matter, with the current accelerated expansion of the Universe driven by dark energy. This model has recently come under scrutiny because of tensions in measurements of the expansion and growth histories of the Universe, parameterized using H0 and S8. The three-dimensional clustering of galaxies encodes key cosmological information that addresses these tensions. Here we present a set of cosmological constraints using simulation-based inference that exploits additional non-Gaussian information on nonlinear scales from galaxy clustering, inaccessible with current analyses. We analyse a subset of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxy survey using SimBIG, a new framework for cosmological inference that leverages high-fidelity simulations and deep generative models. We use two clustering statistics beyond the standard power spectrum: the bispectrum and a summary of the galaxy field based on a convolutional neural network. We constrain H0 and S8 1.5 and 1.9 times more tightly than power spectrum analyses. With this increased precision, our constraints are competitive with those of other cosmological probes, even with only 10% of the full BOSS volume. Future work extending SimBIG to upcoming spectroscopic galaxy surveys (DESI, PFS, Euclid) will produce improved cosmological constraints that will develop understanding of cosmic tensions. By extracting non-Gaussian cosmological information on galaxy clustering at nonlinear scales, a framework for cosmic inference (SimBIG) provides more precise constraints for testing cosmological models.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 11","pages":"1457-1467"},"PeriodicalIF":12.9,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142013853","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 : 2024-08-20DOI: 10.1038/s41550-024-02342-4
Gabriele Pichierri, Alessandro Morbidelli, Konstantin Batygin, Ramon Brasser
TRAPPIST-1 hosts seven planets. The period ratios of neighbouring pairs are close to the 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2 ratios in increasing distance from the star. The Laplace angles associated with neighbouring triplets are observed to be librating, proving the resonant nature of the system. This compact, resonant configuration is a manifest sign of disk-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. Here, we explain the observed orbital configuration with a model that is largely independent of the specific disk migration and orbital circularization efficiencies. Together with migration, the two key elements of our model are that the inner border of the protoplanetary disk receded with time and that the system was initially separated into two subsystems. Specifically, the inner b, c, d and e planets were initially placed in a 3:2 resonance chain and then evolved to the 8:5–5:3 commensurability between planets b, c and d due to the recession of the inner edge of the disk, whereas the outer planets migrated to the inner edge at a later time and established the remaining resonances. Our results pivot on the dynamical role of the presently unobservable recession of the inner edge of protoplanetary disks. They also reveal the role of recurring phases of convergent migration followed by resonant repulsion with associated orbital circularization when resonant chains interact with migration barriers. The dynamical history of the seven-planet TRAPPIST-1 system, which is marked by delicate orbital resonances, is meticulously reconstructed. This study unveils the key physical processes that shaped its formation during and beyond the circumstellar disk phase.
{"title":"The formation of the TRAPPIST-1 system in two steps during the recession of the disk inner edge","authors":"Gabriele Pichierri, Alessandro Morbidelli, Konstantin Batygin, Ramon Brasser","doi":"10.1038/s41550-024-02342-4","DOIUrl":"10.1038/s41550-024-02342-4","url":null,"abstract":"TRAPPIST-1 hosts seven planets. The period ratios of neighbouring pairs are close to the 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2 ratios in increasing distance from the star. The Laplace angles associated with neighbouring triplets are observed to be librating, proving the resonant nature of the system. This compact, resonant configuration is a manifest sign of disk-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. Here, we explain the observed orbital configuration with a model that is largely independent of the specific disk migration and orbital circularization efficiencies. Together with migration, the two key elements of our model are that the inner border of the protoplanetary disk receded with time and that the system was initially separated into two subsystems. Specifically, the inner b, c, d and e planets were initially placed in a 3:2 resonance chain and then evolved to the 8:5–5:3 commensurability between planets b, c and d due to the recession of the inner edge of the disk, whereas the outer planets migrated to the inner edge at a later time and established the remaining resonances. Our results pivot on the dynamical role of the presently unobservable recession of the inner edge of protoplanetary disks. They also reveal the role of recurring phases of convergent migration followed by resonant repulsion with associated orbital circularization when resonant chains interact with migration barriers. The dynamical history of the seven-planet TRAPPIST-1 system, which is marked by delicate orbital resonances, is meticulously reconstructed. This study unveils the key physical processes that shaped its formation during and beyond the circumstellar disk phase.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 11","pages":"1408-1415"},"PeriodicalIF":12.9,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142007480","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 : 2024-08-20DOI: 10.1038/s41550-024-02356-y
While the early 2020s are seeing a resurgence in new space-based X-ray missions — including the NASA-led Imaging X-ray Polarimetry Explorer — a stalwart of the field, Chandra, faces an uncertain future.
虽然在 2020 年代初，新的天基 X 射线任务（包括美国国家航空航天局领导的成像 X 射线极化探测器）正在重新崛起，但该领域的中坚力量钱德拉却面临着不确定的未来。
{"title":"High hopes for high energy","authors":"","doi":"10.1038/s41550-024-02356-y","DOIUrl":"10.1038/s41550-024-02356-y","url":null,"abstract":"While the early 2020s are seeing a resurgence in new space-based X-ray missions — including the NASA-led Imaging X-ray Polarimetry Explorer — a stalwart of the field, Chandra, faces an uncertain future.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 8","pages":"939-939"},"PeriodicalIF":12.9,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41550-024-02356-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142013698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2024-08-20DOI: 10.1038/s41550-024-02347-z
Haiyang Luo, Caroline Dorn, Jie Deng
Water is an important component of exoplanets, with its distribution, that is, whether at the surface or deep inside, fundamentally influencing the planetary properties. The distribution of water in most exoplanets is determined by yet-unknown partition coefficients at extreme conditions. Here we first conduct ab initio molecular dynamics simulations to investigate the metal–silicate partition coefficients of water up to 1,000 GPa and then model planet interiors by considering the effects of water content on density, melting temperature and water partitioning. Our calculations reveal that water strongly partitions into iron over silicate at high pressures and, thus, would preferentially stay in a planet’s core. The results of our planet interior model challenge the notion of water worlds as imagined before: the majority of the bulk water budget (even more than 95%) can be stored deep within the core and the mantle, and not at the surface. For planets more massive than ~6 M⨁ and Earth-size planets (of lower mass and small water budgets), the majority of water resides deep in the cores of planets. Whether water is assumed to be at the surface or at depth can affect the radius up to 15–25% for a given mass. The exoplanets previously believed to be water-poor on the basis of mass–radius data may actually be rich in water. If water exists in super-Earth and sub-Neptune exoplanets, it is expected to be hidden deep in their cores and mantles, rather than at their surfaces. Exoplanets considered to be relatively dry might actually have abundant water sequestered in their interiors.
{"title":"The interior as the dominant water reservoir in super-Earths and sub-Neptunes","authors":"Haiyang Luo, Caroline Dorn, Jie Deng","doi":"10.1038/s41550-024-02347-z","DOIUrl":"10.1038/s41550-024-02347-z","url":null,"abstract":"Water is an important component of exoplanets, with its distribution, that is, whether at the surface or deep inside, fundamentally influencing the planetary properties. The distribution of water in most exoplanets is determined by yet-unknown partition coefficients at extreme conditions. Here we first conduct ab initio molecular dynamics simulations to investigate the metal–silicate partition coefficients of water up to 1,000 GPa and then model planet interiors by considering the effects of water content on density, melting temperature and water partitioning. Our calculations reveal that water strongly partitions into iron over silicate at high pressures and, thus, would preferentially stay in a planet’s core. The results of our planet interior model challenge the notion of water worlds as imagined before: the majority of the bulk water budget (even more than 95%) can be stored deep within the core and the mantle, and not at the surface. For planets more massive than ~6 M⨁ and Earth-size planets (of lower mass and small water budgets), the majority of water resides deep in the cores of planets. Whether water is assumed to be at the surface or at depth can affect the radius up to 15–25% for a given mass. The exoplanets previously believed to be water-poor on the basis of mass–radius data may actually be rich in water. If water exists in super-Earth and sub-Neptune exoplanets, it is expected to be hidden deep in their cores and mantles, rather than at their surfaces. Exoplanets considered to be relatively dry might actually have abundant water sequestered in their interiors.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 11","pages":"1399-1407"},"PeriodicalIF":12.9,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142007481","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 : 2024-08-16DOI: 10.1038/s41550-024-02335-3
A probabilistic machine learning method trained on cosmological simulations is used to determine whether stars in 10,000 nearby galaxies formed internally or were accreted from other galaxies during merging events. The model predicts that only 20% of the stellar mass in present day galaxies is the result of past mergers.
{"title":"Machine learning reveals the merging history of nearby galaxies","authors":"","doi":"10.1038/s41550-024-02335-3","DOIUrl":"10.1038/s41550-024-02335-3","url":null,"abstract":"A probabilistic machine learning method trained on cosmological simulations is used to determine whether stars in 10,000 nearby galaxies formed internally or were accreted from other galaxies during merging events. The model predicts that only 20% of the stellar mass in present day galaxies is the result of past mergers.","PeriodicalId":18778,"journal":{"name":"Nature Astronomy","volume":"8 10","pages":"1218-1219"},"PeriodicalIF":12.9,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141991821","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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