The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantiall...The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantially improved.In this review,we first summarize the cutting-edge states of the exoplanet and disk observations.We further present a comprehensive panoptic view of modern core accretion planet formation scenarios,including dust growth and radial drift,planetesimal formation by the streaming instability,core growth by planetesimal accretion and pebble accretion.We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations.Finally,we point out the critical questions and future directions of planet formation studies.展开更多
With unique orbital and physical characteristics,Triton is a very important target because it may contain information of the origin and evolution of the solar system.Besides space explorations,ground-based observation...With unique orbital and physical characteristics,Triton is a very important target because it may contain information of the origin and evolution of the solar system.Besides space explorations,ground-based observations over long time also play a key role on research of Triton.High-precision positions of Triton obtained from ground telescopes are of great significance for studying its orbital evolution and the physical properties of Neptune.As a long-term observational target,Triton has been observed by the 1.56 m telescope of Shanghai Astronomical Observatory since 1996.In this paper,based on our AAPPDI software and with Gaia DR2 as the reference catalog,604 positions of Triton during 2010–2014 are calculated,with standard errors of 19–88 mas.A comparison between our results and the ephemeris(DE431+nep096)is also given.展开更多
Two-way Doppler measurement is a typical Earth-based radiometric technique for interplanetary spacecraft navigation and gravity science investigation.The most widely used model for the computation of two-way Doppler o...Two-way Doppler measurement is a typical Earth-based radiometric technique for interplanetary spacecraft navigation and gravity science investigation.The most widely used model for the computation of two-way Doppler observables is Moyer’s differenced-range Doppler(DRD) formula,which is based on a Schwarzschild approximation of the Solar-System space-time.However,the computation of range difference in DRD formula is sensitive to round-off errors due to approximate numbers defined by the norm IEEE754 in all PCs.This paper presented two updated models and their corresponding detailed instructions for the computation of the two-way Doppler observables so as to impair the effects of this type of numerical error.These two models were validated by two case studies related to the Rosetta mission—asteroid Lutetia flyby and comet 67 P/Churyumov-Gerasimenko orbiting case.In these two cases,the numerical noise from the updated models can be reduced by two orders-of-magnitude in the computed two-way Doppler observables.The results showed an accuracy from better than 6 × 10^(-3) mm s^(-1) at 1 s counting time interval to better than 3 × 10^(-5) mm s^(-1) at 60 s counting time interval.展开更多
We consider the geometric Titius-Bode rule for the semimajor axes of planetary orbits. We derive an equivalent rule for the midpoints of the segments between consecutive orbits along the radial direction and we interp...We consider the geometric Titius-Bode rule for the semimajor axes of planetary orbits. We derive an equivalent rule for the midpoints of the segments between consecutive orbits along the radial direction and we interpret it physically in terms of the work done in the gravitational field of the Sun by particles whose orbits are perturbed around each planetary orbit. On such energetic grounds, it is not surprising that some exoplanets in multiple-planet extrasolar systems obey the same relation. However,it is surprising that this simple interpretation of the Titius-Bode rule also reveals new properties of the bound closed orbits predicted by Bertrand’s theorem, which has been known since 1873.展开更多
Mars exploration has become a hot spot in recent years and is still advancing rapidly. However, Mars has massive dust storms that may cover many areas of the planet and last for weeks or even months. The local/global ...Mars exploration has become a hot spot in recent years and is still advancing rapidly. However, Mars has massive dust storms that may cover many areas of the planet and last for weeks or even months. The local/global dust storms are so influential that they can significantly reduce visibility, and thereby the images captured by the cameras on the Mars rover are degraded severely. This work presents an unsupervised Martian dust storm removal network via disentangled representation learning(DRL). The core idea of the DRL framework is to use the content encoder and dust storm encoder to disentangle the degraded images into content features(on domain-invariant space) and dust storm features(on domain-specific space). The dust storm features carry the full dust storm-relevant prior knowledge from the dust storm images. The “cleaned” content features can be effectively decoded to generate more natural, faithful, clear images.The primary advantages of this framework are twofold. First, it is among the first to perform unsupervised training in Martian dust storm removal with a single image, avoiding the synthetic data requirements. Second, the model can implicitly learn the dust storm-relevant prior knowledge from the real-world dust storm data sets, avoiding the design of the complicated handcrafted priors. Extensive experiments demonstrate the DRL framework’s effectiveness and show the promising performance of our network for Martian dust storm removal.展开更多
Possible bulk compositions of the super-Earth exoplanets CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate model and a non-standard carbon model. Their internal structures are d...Possible bulk compositions of the super-Earth exoplanets CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate model and a non-standard carbon model. Their internal structures are deduced using a suitable equation of state for the materials. The degeneracy problems of their compo- sitions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) the iron core of CoRoT-7b is not more than 27% of its total mass within lc~ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be com- patible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely to have a Mercury-like composition, with its old age implying that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only super-Earth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.展开更多
Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as t...Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as the beauty of classical dynamics and celestial mechanics attracted me very much, I decided to take celestial mechanics as my research subject and entered university, where a very famous professor of celestial mechanics was a member of the faculty. Then as artificial satellites were launched starting from October 1958, new topics were investigated in the field of celestial mechanics. Moreover, planetary rings, asteroids with moderate values of eccentricity, inclination and so on have become new fields of celestial mechanics. In fact I have tried to solve such problems in an analytical way. Finally, to understand what gravitation is I joined the TAMA300 gravitational wave detector group.展开更多
The technique of X-ray fluorescence remote sensing plays a significant role in research related to the chemical compositions of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectro...The technique of X-ray fluorescence remote sensing plays a significant role in research related to the chemical compositions of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectrometer in detail and present the preliminary results about the first global Mg/Si and Al/Si maps of the lunar surface. Our results show that the distributions of Mg/Si and Al/Si correlate well with terrains on the Moon. The higher Mg/Si ratio corresponds to the mare regions while the lower value corresponds to the highland terrains. The map of the Al/Si ratio shows a reversed distribution compared with the map of the Mg/Si ratio.展开更多
基金supported by the European Research Council(ERC Consolidator Grant 724687-PLANETESYS)the Swedish Walter Gyllenberg Foundation+3 种基金start-up grant of Bairen program from Zhejiang Universitysupported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the National Natural Science Foundation of China(Grant Nos.12033010 and 11773081)CAS Interdisciplinary Innovation Team and Foundation of Minor Planets of the Purple Mountain Observatory。
文摘The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade.Benefitting from that,our global understanding of the planet formation processes has been substantially improved.In this review,we first summarize the cutting-edge states of the exoplanet and disk observations.We further present a comprehensive panoptic view of modern core accretion planet formation scenarios,including dust growth and radial drift,planetesimal formation by the streaming instability,core growth by planetesimal accretion and pebble accretion.We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations.Finally,we point out the critical questions and future directions of planet formation studies.
基金the financial support of the National Natural Science Foundation of China(Grant Nos.11803019,12073062 and 11703007)the Hubei Provincial Department of Education(Grant No.B2020162)。
文摘With unique orbital and physical characteristics,Triton is a very important target because it may contain information of the origin and evolution of the solar system.Besides space explorations,ground-based observations over long time also play a key role on research of Triton.High-precision positions of Triton obtained from ground telescopes are of great significance for studying its orbital evolution and the physical properties of Neptune.As a long-term observational target,Triton has been observed by the 1.56 m telescope of Shanghai Astronomical Observatory since 1996.In this paper,based on our AAPPDI software and with Gaia DR2 as the reference catalog,604 positions of Triton during 2010–2014 are calculated,with standard errors of 19–88 mas.A comparison between our results and the ephemeris(DE431+nep096)is also given.
基金supported by the National Natural Science Foundation of China (Grant Nos.42030110,41874010 and U1831132)Hubei Province Foundation innovation group project (2018CFA087)+1 种基金funded by a DAR grant in planetology from the French Space Agency (CNES)funded by Deutsches Zentrum für Luft-und Raumfahrt,Bonn-Oberkassel (Grant Nos.50QM1704 and 50QM1901)。
文摘Two-way Doppler measurement is a typical Earth-based radiometric technique for interplanetary spacecraft navigation and gravity science investigation.The most widely used model for the computation of two-way Doppler observables is Moyer’s differenced-range Doppler(DRD) formula,which is based on a Schwarzschild approximation of the Solar-System space-time.However,the computation of range difference in DRD formula is sensitive to round-off errors due to approximate numbers defined by the norm IEEE754 in all PCs.This paper presented two updated models and their corresponding detailed instructions for the computation of the two-way Doppler observables so as to impair the effects of this type of numerical error.These two models were validated by two case studies related to the Rosetta mission—asteroid Lutetia flyby and comet 67 P/Churyumov-Gerasimenko orbiting case.In these two cases,the numerical noise from the updated models can be reduced by two orders-of-magnitude in the computed two-way Doppler observables.The results showed an accuracy from better than 6 × 10^(-3) mm s^(-1) at 1 s counting time interval to better than 3 × 10^(-5) mm s^(-1) at 60 s counting time interval.
文摘We consider the geometric Titius-Bode rule for the semimajor axes of planetary orbits. We derive an equivalent rule for the midpoints of the segments between consecutive orbits along the radial direction and we interpret it physically in terms of the work done in the gravitational field of the Sun by particles whose orbits are perturbed around each planetary orbit. On such energetic grounds, it is not surprising that some exoplanets in multiple-planet extrasolar systems obey the same relation. However,it is surprising that this simple interpretation of the Titius-Bode rule also reveals new properties of the bound closed orbits predicted by Bertrand’s theorem, which has been known since 1873.
基金supported by the National Key R&D Program of China (No. 2021YFA1600504)the National Natural Science Foundation of China (NSFC)(Nos. 11790305,62132002 and 61922006)。
文摘Mars exploration has become a hot spot in recent years and is still advancing rapidly. However, Mars has massive dust storms that may cover many areas of the planet and last for weeks or even months. The local/global dust storms are so influential that they can significantly reduce visibility, and thereby the images captured by the cameras on the Mars rover are degraded severely. This work presents an unsupervised Martian dust storm removal network via disentangled representation learning(DRL). The core idea of the DRL framework is to use the content encoder and dust storm encoder to disentangle the degraded images into content features(on domain-invariant space) and dust storm features(on domain-specific space). The dust storm features carry the full dust storm-relevant prior knowledge from the dust storm images. The “cleaned” content features can be effectively decoded to generate more natural, faithful, clear images.The primary advantages of this framework are twofold. First, it is among the first to perform unsupervised training in Martian dust storm removal with a single image, avoiding the synthetic data requirements. Second, the model can implicitly learn the dust storm-relevant prior knowledge from the real-world dust storm data sets, avoiding the design of the complicated handcrafted priors. Extensive experiments demonstrate the DRL framework’s effectiveness and show the promising performance of our network for Martian dust storm removal.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10833001 and 10925313)Ph.D traininggrant of China (20090091110002)+1 种基金Fundamental Research Funds for the Central Universities(No. 1112020102)support from the Shandong Provincial Natural Science Foundation,China (ZR2010AQ023)
文摘Possible bulk compositions of the super-Earth exoplanets CoRoT-7b, Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate model and a non-standard carbon model. Their internal structures are deduced using a suitable equation of state for the materials. The degeneracy problems of their compo- sitions can be partly overcome, based on the fact that all three planets are extremely close to their host stars. By analyzing the numerical results, we conclude: 1) the iron core of CoRoT-7b is not more than 27% of its total mass within lc~ mass-radius error bars, so an Earth-like composition is less likely, but its carbon rich model can be com- patible with an Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely to have a Mercury-like composition, with its old age implying that its high iron content may be a result of strong solar wind or giant impact; 3) the transiting-only super-Earth Kepler-9d is also discussed. Combining its possible composition with the formation theory, we can place some constraints on its mass and bulk composition.
文摘Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as the beauty of classical dynamics and celestial mechanics attracted me very much, I decided to take celestial mechanics as my research subject and entered university, where a very famous professor of celestial mechanics was a member of the faculty. Then as artificial satellites were launched starting from October 1958, new topics were investigated in the field of celestial mechanics. Moreover, planetary rings, asteroids with moderate values of eccentricity, inclination and so on have become new fields of celestial mechanics. In fact I have tried to solve such problems in an analytical way. Finally, to understand what gravitation is I joined the TAMA300 gravitational wave detector group.
基金supported by the Science and Technology Development Fund of Macao (Grant Nos.068/2011/A,048/2012/A2,039/2013/A2,091/2013/A3 and 020/2014/A1)by the Key Research Program of the Chinese Academy of Sciences (Grant No.KGZD-EW603)
文摘The technique of X-ray fluorescence remote sensing plays a significant role in research related to the chemical compositions of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectrometer in detail and present the preliminary results about the first global Mg/Si and Al/Si maps of the lunar surface. Our results show that the distributions of Mg/Si and Al/Si correlate well with terrains on the Moon. The higher Mg/Si ratio corresponds to the mare regions while the lower value corresponds to the highland terrains. The map of the Al/Si ratio shows a reversed distribution compared with the map of the Mg/Si ratio.