In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We ex...In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We extracted morphological features through image enhancement techniques and calculated the dust activity parameter,Afρ,along with dust mass loss rates and coma color indices using broadband photometric data.Our morphological analysis uncovered a spectrum of dust characteristics among the observed comets,ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/Swift-Gehrels.The Afρvalues varied between 148.8±0.3 cm for 64P/Swift-Gehrels and1118.5±6.2 cm for C/2017 M4(ATLAS)(measured within a reference aperture radius ofρ=6″),indicating a range from moderate to high activity levels.Dust mass loss rates were estimated from 328.1 kg s^(-1)for comet 64P/Swift-Gehrels to 1395.5 kg s^(-1)for comet C/2017 M4(ATLAS).The color indices of comets 38P/Stephan-Oterma and C/2017 M4(ATLAS)closely resemble the average colors of active short-period comets and active longperiod comets,respectively.In contrast,64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.展开更多
We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leona...We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leonard),and 67P/Churyumov-Gerasimenko during or after their perihelion passages.Thousands of molecular transition lines fall in this low-frequency range,many attributed to complex organic or prebiotic molecules.We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data.Although several molecules have been detected at high frequencies of greater than100 GHz in comets,our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges.The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines,which could be caused by the masers or non-LTE effects.Although the line strengths are predicted to be weak,for FAST,using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.展开更多
Objective A new technique of transthoracic lung ultrasonography(TLS) has emerged and demonstrated promising results in acute heart failure diagnosis at an early stage. However, the diagnostic value of ultrasound lung ...Objective A new technique of transthoracic lung ultrasonography(TLS) has emerged and demonstrated promising results in acute heart failure diagnosis at an early stage. However, the diagnostic value of ultrasound lung comets(ULCs) for acute heart failure(AHF) performed in busy emergency department(ED) is uncertain. The present meta-analysis aimed to assess the diagnostic efficiency of ULCs in AHF. Methods We conducted a search on online journal databases to collect the data on TLS performed for diagnosing AHF published up to the end of July 2017. The sensitivity, specificity, positive likelihood ratio(PLR), negative likelihood ratio(NLR), and summary receiver operating characteristic(SROC) curve were calculated. The post-test probability of AHF was calculated by using Bayes analysis. Results We enrolled a total of 15 studies involving 3,309 patients. The value of sensitivity, specificity, PLR, NLR, DOR, area under the SROC curve, and Q* index was 85%, 91%, 8.94, 0.14, 67.24, 0.9587, and 0.9026, respectively. We detected significant heterogeneity among included studies, and therefore, all these results were analyzed under the random-effect model. We also explored possible sources of heterogeneity among the studies by using meta-regression analysis. Results suggest that the time interval between patient’s admission to bedside TLS examination was closely related to TLS accuracy. Conclusion This meta-analysis demonstrated that detecting ULCs is a convenient bedside tool and has high accuracy for early AHF diagnosis in ED. TLS could be recommended to be applied for early diagnosis of AHF in ED.展开更多
We present simulation results on evolution development of orbital motion of short-period comets with the revolution period not exceeding 6-7 years, namely comets 21P/Giacobini-Zinner, 26P/Grigg- Skjellerup and 7P/Pons...We present simulation results on evolution development of orbital motion of short-period comets with the revolution period not exceeding 6-7 years, namely comets 21P/Giacobini-Zinner, 26P/Grigg- Skjellerup and 7P/Pons-Winnecke. The calculations cover the range from the date of the object＇s discovery to 2100. Variations in the objects＇ orbital elements under the action of gravity disturbances, taking Earth＇s gravitational potential into account when the small body approaches, are analyzed. Corrected dates of peri- helion passages can be used for scheduling observations.展开更多
SUISEI is a suite of computational tools that has been developed over the past three decades and successfully applied to comets;including ComChem, a global, multi-fluid gas dynamics simulation with detailed chemical k...SUISEI is a suite of computational tools that has been developed over the past three decades and successfully applied to comets;including ComChem, a global, multi-fluid gas dynamics simulation with detailed chemical kinetics of the cometary coma;ComDust, a model of comet dust evolution and interaction with gas;and ComNuc, a 3-D simulation of gas and heat flow within the comet nucleus porous subsurface layers. The combination of these tools have resulted in an improved knowledge of chemical species in the comet’s coma and their relationship to native molecules in the nucleus ices by analyzing space- and ground-based observations and in situ measurements from spacecraft missions. A review of SUISEI is presented and applications are made to two cases: chemical recycling of HCN in comets and the physical conditions of the near-Sun object, 3200 Phaethon.展开更多
Since the concept of Nongravitational Force (hereafter NF) was first proposed a century and a half ago, different models of it have been suggested and being modified. Its effect on the orbital motions of comets has be...Since the concept of Nongravitational Force (hereafter NF) was first proposed a century and a half ago, different models of it have been suggested and being modified. Its effect on the orbital motions of comets has been studied. Especially, some researchers have attempted to draw some inclues of the physical nature of the cometary nucleus from the NF parameters. In this paper, we try to give a concise review about the different models of NF and their effects on orbit computation. And then, we will try to detect whether there is nongravitational effect on Comet Hale-Bopp’s orbital motion using Style II NF model.展开更多
Although people have studied comets for a long time and used spacecraft to detect comets in a short distance,the formation time and causes of comets are still unresolved.Therefore,according to the formation and evolut...Although people have studied comets for a long time and used spacecraft to detect comets in a short distance,the formation time and causes of comets are still unresolved.Therefore,according to the formation and evolution law of planets and the dynamic mechanism,the author thoroughly revealed the formation and evolution of comets:A powerful storm cyclone on Neptune,such as the Great Dark Spot,can involve a large number of clouds.These clouds are gradually cooled and compressed in the process of rapidly sinking along the spiral path,and then condense into huge water ice crystals at the bottom of the cyclone;When such a crystal falls into a deep hole filled with liquid hydrogen,it is easy to collide violently with the boulders in the hole,and instantly ignite the liquid hydrogen in the hole.Under the strong push of high-pressure gas,some fragments of the ice crystal can quickly reach a very high initial speed.Especially when the jet direction of the Great Dark Spot is consistent with the direction of Neptune’s revolution speed,such fragments can quickly reach Neptune’s escape speed of 23.56 km/s.Therefore,the fragments can break away from Neptune and enter an elliptical orbit around the sun,becoming a comet.Similarly,when the metal hydrogen at the bottom of a Great Red Spot on Jupiter explodes in a series,the fragments ejected from the Great Red Spot can reach the escape speed of Jupiter of 60 km/s,therefore,such fragments can break away from Jupiter and enter the elliptical orbit around the sun to become comets.Many of these comets can become asteroids in the asteroid belt,which is the formation principle of the asteroid belt.展开更多
The historical records of astronomical phenomena may play a significant role in comet identification.Getting an accurate result is based on many factors,of which the calculation of orbital elements is the most importa...The historical records of astronomical phenomena may play a significant role in comet identification.Getting an accurate result is based on many factors,of which the calculation of orbital elements is the most important.This paper presents a "Cross Reference" method in which the perturbation of Jupiter is the only considered factor used to attempt an efficient way of comet identification with ancient Chinese historical records.In this method,the records before and after the calculated result from orbital determination within the error range are compared with the historical records to find the correlated perihelion time,and then,with five other orbital elements at the perihelion time,the ephemeris is calculated.If the calculated ephemeris matches the historical records,it is concluded that the comet determined by orbital calculation is the same as the one recorded in history.With this method,three comets with four historical records have already been found.展开更多
One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific object...One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific objectives,measurement targets,and measurement requirements for the proposed Gas and Ion Analyzer(GIA).The GIA is designed for in-situ mass spectrometry of neutral gases and low-energy ions,such as hydrogen,carbon,and oxygen,in the vicinity of 311P.Ion sampling techniques are essential for the GIA's Time-of-Flight(TOF)mass analysis capabilities.In this paper,we present an enhanced ion sampling technique through the development of an ion attraction model and an ion source model.The ion attraction model demonstrates that adjusting attraction grid voltage can enhance the detection efficiency of low-energy ions and mitigate the repulsive force of ions during sampling,which is influenced by the satellite's surface positive charging.The ion source model simulates the processes of gas ionization and ion multiplication.Simulation results indicate that the GIA can achieve a lower pressure limit below 10-13Pa and possess a dynamic range exceeding 10~9.These performances ensure the generation of ions with stable and consistent current,which is crucial for high-resolution and broad dynamic range mass spectrometer analysis.Preliminary testing experiments have verified GIA's capability to detect gas compositions such as H2O and N2.In-situ measurements near 311P using GIA are expected to significantly contribute to our understanding of asteroid activity mechanisms,the evolution of the atmospheric and ionized environments of main-belt comets,the interactions with solar wind,and the origin of Earth's water.展开更多
Sent out at 1:31am GMT+8 on May 29 by a Long March-3B carrier rocket from the Xichang Satellite Launch Center in Sichuan province,China,Tianwen-2,the second mission of China’s Planetary Exploration Program,correctly ...Sent out at 1:31am GMT+8 on May 29 by a Long March-3B carrier rocket from the Xichang Satellite Launch Center in Sichuan province,China,Tianwen-2,the second mission of China’s Planetary Exploration Program,correctly entered the transfer trajectory toward an asteroid named 2016HO3 after flying for 18 minutes.Its solar wings unfolded properly,signaling a successful start,and primed for the next stage of its mission.展开更多
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China(grant No.2021D01B112)Tianshan Talent Training Program through the grant 2023TSYCCX0101。
文摘In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We extracted morphological features through image enhancement techniques and calculated the dust activity parameter,Afρ,along with dust mass loss rates and coma color indices using broadband photometric data.Our morphological analysis uncovered a spectrum of dust characteristics among the observed comets,ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/Swift-Gehrels.The Afρvalues varied between 148.8±0.3 cm for 64P/Swift-Gehrels and1118.5±6.2 cm for C/2017 M4(ATLAS)(measured within a reference aperture radius ofρ=6″),indicating a range from moderate to high activity levels.Dust mass loss rates were estimated from 328.1 kg s^(-1)for comet 64P/Swift-Gehrels to 1395.5 kg s^(-1)for comet C/2017 M4(ATLAS).The color indices of comets 38P/Stephan-Oterma and C/2017 M4(ATLAS)closely resemble the average colors of active short-period comets and active longperiod comets,respectively.In contrast,64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.
基金supported by a grant from the National Natural Science Foundation of China(NSFC)No.11988101by the NSFC grant Nos.11703047,11773041,U2031119,12173052,12173053,12373032,and 11963002+6 种基金support from the China Postdoctoral Science Foundation grant No.2023M733271the Foundation of Education Bureau of Guizhou Province,China(grant No.KY(2020)003)supported by the International Partnership Program of the Chinese Academy of Sciences,program No.114A11KYSB20210010the Youth Innovation Promotion Association of the Chinese Academy of Sciences(ID Nos.2023064,2018075,and Y2022027)the support from the National Key R&D Program of China grant Nos.2022YFC2205202 and 2020SKA0120100supported by the CAS“Light of West China”Programthe support by the NSFC grant No.12373026。
文摘We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leonard),and 67P/Churyumov-Gerasimenko during or after their perihelion passages.Thousands of molecular transition lines fall in this low-frequency range,many attributed to complex organic or prebiotic molecules.We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data.Although several molecules have been detected at high frequencies of greater than100 GHz in comets,our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges.The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines,which could be caused by the masers or non-LTE effects.Although the line strengths are predicted to be weak,for FAST,using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.
基金supported by the capital characteristic clinic project of China [Z151100004015071]National Natural Science Foundation of China [51573211]ruiyi emergency medical research fund of China [R2017013]
文摘Objective A new technique of transthoracic lung ultrasonography(TLS) has emerged and demonstrated promising results in acute heart failure diagnosis at an early stage. However, the diagnostic value of ultrasound lung comets(ULCs) for acute heart failure(AHF) performed in busy emergency department(ED) is uncertain. The present meta-analysis aimed to assess the diagnostic efficiency of ULCs in AHF. Methods We conducted a search on online journal databases to collect the data on TLS performed for diagnosing AHF published up to the end of July 2017. The sensitivity, specificity, positive likelihood ratio(PLR), negative likelihood ratio(NLR), and summary receiver operating characteristic(SROC) curve were calculated. The post-test probability of AHF was calculated by using Bayes analysis. Results We enrolled a total of 15 studies involving 3,309 patients. The value of sensitivity, specificity, PLR, NLR, DOR, area under the SROC curve, and Q* index was 85%, 91%, 8.94, 0.14, 67.24, 0.9587, and 0.9026, respectively. We detected significant heterogeneity among included studies, and therefore, all these results were analyzed under the random-effect model. We also explored possible sources of heterogeneity among the studies by using meta-regression analysis. Results suggest that the time interval between patient’s admission to bedside TLS examination was closely related to TLS accuracy. Conclusion This meta-analysis demonstrated that detecting ULCs is a convenient bedside tool and has high accuracy for early AHF diagnosis in ED. TLS could be recommended to be applied for early diagnosis of AHF in ED.
文摘We present simulation results on evolution development of orbital motion of short-period comets with the revolution period not exceeding 6-7 years, namely comets 21P/Giacobini-Zinner, 26P/Grigg- Skjellerup and 7P/Pons-Winnecke. The calculations cover the range from the date of the object＇s discovery to 2100. Variations in the objects＇ orbital elements under the action of gravity disturbances, taking Earth＇s gravitational potential into account when the small body approaches, are analyzed. Corrected dates of peri- helion passages can be used for scheduling observations.
文摘SUISEI is a suite of computational tools that has been developed over the past three decades and successfully applied to comets;including ComChem, a global, multi-fluid gas dynamics simulation with detailed chemical kinetics of the cometary coma;ComDust, a model of comet dust evolution and interaction with gas;and ComNuc, a 3-D simulation of gas and heat flow within the comet nucleus porous subsurface layers. The combination of these tools have resulted in an improved knowledge of chemical species in the comet’s coma and their relationship to native molecules in the nucleus ices by analyzing space- and ground-based observations and in situ measurements from spacecraft missions. A review of SUISEI is presented and applications are made to two cases: chemical recycling of HCN in comets and the physical conditions of the near-Sun object, 3200 Phaethon.
文摘Since the concept of Nongravitational Force (hereafter NF) was first proposed a century and a half ago, different models of it have been suggested and being modified. Its effect on the orbital motions of comets has been studied. Especially, some researchers have attempted to draw some inclues of the physical nature of the cometary nucleus from the NF parameters. In this paper, we try to give a concise review about the different models of NF and their effects on orbit computation. And then, we will try to detect whether there is nongravitational effect on Comet Hale-Bopp’s orbital motion using Style II NF model.
文摘Although people have studied comets for a long time and used spacecraft to detect comets in a short distance,the formation time and causes of comets are still unresolved.Therefore,according to the formation and evolution law of planets and the dynamic mechanism,the author thoroughly revealed the formation and evolution of comets:A powerful storm cyclone on Neptune,such as the Great Dark Spot,can involve a large number of clouds.These clouds are gradually cooled and compressed in the process of rapidly sinking along the spiral path,and then condense into huge water ice crystals at the bottom of the cyclone;When such a crystal falls into a deep hole filled with liquid hydrogen,it is easy to collide violently with the boulders in the hole,and instantly ignite the liquid hydrogen in the hole.Under the strong push of high-pressure gas,some fragments of the ice crystal can quickly reach a very high initial speed.Especially when the jet direction of the Great Dark Spot is consistent with the direction of Neptune’s revolution speed,such fragments can quickly reach Neptune’s escape speed of 23.56 km/s.Therefore,the fragments can break away from Neptune and enter an elliptical orbit around the sun,becoming a comet.Similarly,when the metal hydrogen at the bottom of a Great Red Spot on Jupiter explodes in a series,the fragments ejected from the Great Red Spot can reach the escape speed of Jupiter of 60 km/s,therefore,such fragments can break away from Jupiter and enter the elliptical orbit around the sun to become comets.Many of these comets can become asteroids in the asteroid belt,which is the formation principle of the asteroid belt.
基金supported by theNational Natural Science Foundation of China (Grant No.10821061)the National Basic Research Program of China (Grant No.2007CB815103)
文摘The historical records of astronomical phenomena may play a significant role in comet identification.Getting an accurate result is based on many factors,of which the calculation of orbital elements is the most important.This paper presents a "Cross Reference" method in which the perturbation of Jupiter is the only considered factor used to attempt an efficient way of comet identification with ancient Chinese historical records.In this method,the records before and after the calculated result from orbital determination within the error range are compared with the historical records to find the correlated perihelion time,and then,with five other orbital elements at the perihelion time,the ephemeris is calculated.If the calculated ephemeris matches the historical records,it is concluded that the comet determined by orbital calculation is the same as the one recorded in history.With this method,three comets with four historical records have already been found.
基金Supported by the National Natural Science Foundation of China(42474239,41204128)China National Space Administration(Pre-research project on Civil Aerospace Technologies No.D010301)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA17010303)。
文摘One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific objectives,measurement targets,and measurement requirements for the proposed Gas and Ion Analyzer(GIA).The GIA is designed for in-situ mass spectrometry of neutral gases and low-energy ions,such as hydrogen,carbon,and oxygen,in the vicinity of 311P.Ion sampling techniques are essential for the GIA's Time-of-Flight(TOF)mass analysis capabilities.In this paper,we present an enhanced ion sampling technique through the development of an ion attraction model and an ion source model.The ion attraction model demonstrates that adjusting attraction grid voltage can enhance the detection efficiency of low-energy ions and mitigate the repulsive force of ions during sampling,which is influenced by the satellite's surface positive charging.The ion source model simulates the processes of gas ionization and ion multiplication.Simulation results indicate that the GIA can achieve a lower pressure limit below 10-13Pa and possess a dynamic range exceeding 10~9.These performances ensure the generation of ions with stable and consistent current,which is crucial for high-resolution and broad dynamic range mass spectrometer analysis.Preliminary testing experiments have verified GIA's capability to detect gas compositions such as H2O and N2.In-situ measurements near 311P using GIA are expected to significantly contribute to our understanding of asteroid activity mechanisms,the evolution of the atmospheric and ionized environments of main-belt comets,the interactions with solar wind,and the origin of Earth's water.
文摘Sent out at 1:31am GMT+8 on May 29 by a Long March-3B carrier rocket from the Xichang Satellite Launch Center in Sichuan province,China,Tianwen-2,the second mission of China’s Planetary Exploration Program,correctly entered the transfer trajectory toward an asteroid named 2016HO3 after flying for 18 minutes.Its solar wings unfolded properly,signaling a successful start,and primed for the next stage of its mission.
