A first-order question in the studies of the Solar System is how its outer zone known as the Kuiper belt was created and evolved.Two end-member models, involving coagulation vs. streaming instability, make different p...A first-order question in the studies of the Solar System is how its outer zone known as the Kuiper belt was created and evolved.Two end-member models, involving coagulation vs. streaming instability, make different predictions-testable by the cratering history of Kuiper Belt Objects(KBOs)-about the cumulative size-frequency distribution(SFD) of the KBOs. Among all of the imaged KBOs, Pluto’s largest icy moon, Charon, appears to preserve the largest size range of seemingly undisturbed craters, their diameters(D) on Charon ranging from < 1 km to > 220 km. Current work shows that Charon’s craters with D < 10-20 km are fewer than those expected by the coagulation mechanism, but whether this is an artifact of post-cratering modification of smaller craters is unknown. We address this issue by conducting systematic photogeological mapping and performing detailed landform analysis using the highest resolution images obtained by the New Horizons spacecraft, which reveal a range of differentiable terrains on Charon. The most important findings of our work include(1) truncation and obliteration of large craters(diameters > 30-40 km) and their crater rim ridges along the eastern edges of several north-trending, eastward-convex, arcuate ranges in Oz Terra of the northern encountered hemisphere,(2) lobate ridges, lobate knob trains, and lobate aprons resembling glacial moraine landforms on Earth,(3) dendritic channel systems containing hanging valleys,and(4) locally striated surfaces defined by parallel ridges, knob trains, and grooves that are > 40-50 km in length. The above observations and the topographic dichotomy of Charon’s encountered hemisphere can be explained by a landscape-evolution model that involves(i)a giant impact that created the Vulcan Planitia basin and the extensional fault zone along its northern rim,(ii) a transient atmosphere capable of driving N2-ice glacial erosion of the water-ice bedrock and transporting water-ice debris to sedimentary basins,(iii) regional glacial erosion and transport of earlier emplaced impact ejecta deposits from the highlands of Oz Terra into the lowland basin of Vulcan Planitia,(iv) syn-glaciation north-trending thrusting, interpreted to have been induced by Charon’s despinning, and(v) the development of a water-ice debris cover layer over subsurface N2 ice below Vulcan Planitia during global deglaciation. The infilling of the Vulcan Planitia could have been accompanied by cryovolcanism. The extensive modification of impact craters means that the size-frequency distributions of Charon’s craters should serve only as a lower bound when used to test formation mechanisms proposed for Kuiper belt objects.展开更多
The orbital migration of Jovian planets is believed to have played an important role in shaping the Kuiper Belt. We investigate the effects of the long time-scale （2 ×107 yr） migration of Jovian planets on the ...The orbital migration of Jovian planets is believed to have played an important role in shaping the Kuiper Belt. We investigate the effects of the long time-scale （2 ×107 yr） migration of Jovian planets on the orbital evolution of massless test particles that are initially located beyond 28 AU. Because of the slowness of the migration, Neptune＇s mean motion resonances capture test particles very efficiently. Taking into account the stochastic behavior during the planetary migration and for proper parameter values, the resulting concentration of objects in the 3：2 resonance is prominent, while very few objects enter the 2：1 resonance, thus matching the observed Kuiper Belt objects very well. We also find that such a long time-scale migration is favorable for exciting the inclinations of the test particles, because it makes the secular resonance possible to operate during the migration. Our analyses show that the us secular resonance excites the eccentricities of some test particles, so decreasing their perihelion distances, leading to close encounters with Neptune, which can then pump the inclinations up to 20°.展开更多
Despite Pluto’s demotion to dwarf planet status,people are still attached to it.Scientists combined observations of Pluto from NASA’s New Horizons probe with observations of comet Churyumov-Gerasimenko from the Euro...Despite Pluto’s demotion to dwarf planet status,people are still attached to it.Scientists combined observations of Pluto from NASA’s New Horizons probe with observations of comet Churyumov-Gerasimenko from the European Space Agency’s Rosetta probe and found that Pluto’s nitrogen abundance matched the pattern of about a billion comets,which led to the theory that Pluto is made of about a billion comets.Yet they don’t know exactly when or where these comets originated.By studying the origin and orbit of comets,the author of this paper found that the material that condensed Pluto was mainly comets and dust ejected by Neptune,and the Kuiper Belt objects were condensed by material ejected by Neptune toward the outer side of its orbit.展开更多
太阳星云气体的耗散可以引起长期共振迁移（secular resonance sweeping，SRS），当长期共振的位置扫过经典Kuiper带小天体（Kuiper Belt objects，KBOs），就会激发其轨道倾角．详细研究了在太阳系紧致构形中（指四个大行星轨道彼此相...太阳星云气体的耗散可以引起长期共振迁移（secular resonance sweeping，SRS），当长期共振的位置扫过经典Kuiper带小天体（Kuiper Belt objects，KBOs），就会激发其轨道倾角．详细研究了在太阳系紧致构形中（指四个大行星轨道彼此相距较小的状态）SRS对经典KBOs轨道倾角的激发过程，发现KBOs轨道倾角受激发的程度敏感地依赖于星云气体中面与太阳系不变平面^1 的夹角δ：当星云气体中面与不变平面重合，即δ=0时，经典KBOs倾角受到的激发很小；而当星云气体中面与黄道面重合，即δ≈1．6^。时，在合理的初始条件下，经典KBOs的倾角最高可以被激发到30^。以上,另外，通过模拟木星具有较大轨道倾角的情形以及SRS和大行星轨道迁移同时发生的情形，发现对于经典KBOs倾角的受激发程度而言，它们两者的影响都远弱于6．展开更多
受地球大气影响,使用地基光学望远镜观测角距离较小的双星系统或主卫星系统时往往会出现星象不可分辨的情况.因此,系统光心位置与系统质心位置可能存在一定的偏差.准确地测量太阳系天体系统质心位置可以改进其轨道参数,有助于揭示太阳...受地球大气影响,使用地基光学望远镜观测角距离较小的双星系统或主卫星系统时往往会出现星象不可分辨的情况.因此,系统光心位置与系统质心位置可能存在一定的偏差.准确地测量太阳系天体系统质心位置可以改进其轨道参数,有助于揭示太阳系的形成与演化.以矮行星Haumea及其亮卫星Hi’iaka的运动为例,仿真系统光心围绕质心扰动的过程,探究视宁度(用星象的半高全宽表示)变化对准确测量光心位置的影响.仿真结果表明,使用二维高斯定心算法测定的系统光心位置随视宁度变化,而修正矩定心算法的定心结果不受视宁度的影响.根据仿真结果,研究能够有效减少视宁度变化对光心位置准确测量影响的定心算法十分必要;同时,新的定心算法还需考虑主星光度变化的影响.使用云南天文台2.4 m望远镜, 1 m望远镜以及紫金山天文台姚安观测站0.8 m望远镜从2022年2月7日至2022年5月25日观测矮行星Haumea系统,得到29晚共463幅CCD图像.新定心算法确定的光心位置与使用二维高斯定心算法的结果相比具有更好的位置拟合效果.此外,还发现亮卫星Hi’iaka在Jet Propulsion Laboratory (JPL)历表与Institut de Mécanique Céleste et de Calcul des éphémérides (IMCCE)历表中的位置存在较大偏差.展开更多
The population of Neptune Trojans is believed to be bigger than that of Jupiter Trojans and that of asteroids in the main belt, although only eight members of this distant asteroid swarm have been observed up to now. ...The population of Neptune Trojans is believed to be bigger than that of Jupiter Trojans and that of asteroids in the main belt, although only eight members of this distant asteroid swarm have been observed up to now. Six leading Neptune Trojans around the Lagrange point L4 discovered earlier have been studied in detail, but two trailing ones found recently around the L5 point, 2004 KV18 and 2008 LC18, have not yet been investigated. We report our investigations on the dynamical behaviors of these two new Neptune Trojans. Our calculations show that the asteroid 2004 KV18 is a temporary Neptune Trojan. Most probably, it was captured into the trailing Trojan cloud no earlier than 2.03 ×105 yr ago, and it will not maintain this position later than 1.65 × 105 yr in the future. Based on the statistics from our orbital simulations, we ar- gue that this object is more like a scattered Kuiper belt object. By contrast, the orbit of 2008 LC18 is much more stable. Among the clone orbits spreading within the orbital uncertainties, a considerable portion of clones may survive on the L5 tadpole orbits for 4 Gyr. The strong dependence of the stability on the semimajor axis and resonant angle suggests that further observations are badly required to constrain the orbit in the stable region. We also discuss the implications of the existence and dynamics of these two trailing Trojans over the history of the solar system.展开更多
We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radia...We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified CRTBP.We have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun–Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun–Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter μ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of μ for achieving stability. We remark that the stability range of μ in non-collinear equilibrium points depends on the perturbing parameters. In the context of the Sun–Haumea system, we have found that the non-collinear equilibrium points are stable.展开更多
文摘A first-order question in the studies of the Solar System is how its outer zone known as the Kuiper belt was created and evolved.Two end-member models, involving coagulation vs. streaming instability, make different predictions-testable by the cratering history of Kuiper Belt Objects(KBOs)-about the cumulative size-frequency distribution(SFD) of the KBOs. Among all of the imaged KBOs, Pluto’s largest icy moon, Charon, appears to preserve the largest size range of seemingly undisturbed craters, their diameters(D) on Charon ranging from < 1 km to > 220 km. Current work shows that Charon’s craters with D < 10-20 km are fewer than those expected by the coagulation mechanism, but whether this is an artifact of post-cratering modification of smaller craters is unknown. We address this issue by conducting systematic photogeological mapping and performing detailed landform analysis using the highest resolution images obtained by the New Horizons spacecraft, which reveal a range of differentiable terrains on Charon. The most important findings of our work include(1) truncation and obliteration of large craters(diameters > 30-40 km) and their crater rim ridges along the eastern edges of several north-trending, eastward-convex, arcuate ranges in Oz Terra of the northern encountered hemisphere,(2) lobate ridges, lobate knob trains, and lobate aprons resembling glacial moraine landforms on Earth,(3) dendritic channel systems containing hanging valleys,and(4) locally striated surfaces defined by parallel ridges, knob trains, and grooves that are > 40-50 km in length. The above observations and the topographic dichotomy of Charon’s encountered hemisphere can be explained by a landscape-evolution model that involves(i)a giant impact that created the Vulcan Planitia basin and the extensional fault zone along its northern rim,(ii) a transient atmosphere capable of driving N2-ice glacial erosion of the water-ice bedrock and transporting water-ice debris to sedimentary basins,(iii) regional glacial erosion and transport of earlier emplaced impact ejecta deposits from the highlands of Oz Terra into the lowland basin of Vulcan Planitia,(iv) syn-glaciation north-trending thrusting, interpreted to have been induced by Charon’s despinning, and(v) the development of a water-ice debris cover layer over subsurface N2 ice below Vulcan Planitia during global deglaciation. The infilling of the Vulcan Planitia could have been accompanied by cryovolcanism. The extensive modification of impact craters means that the size-frequency distributions of Charon’s craters should serve only as a lower bound when used to test formation mechanisms proposed for Kuiper belt objects.
基金Supported by the National Natural Science Foundation of China.
文摘The orbital migration of Jovian planets is believed to have played an important role in shaping the Kuiper Belt. We investigate the effects of the long time-scale （2 ×107 yr） migration of Jovian planets on the orbital evolution of massless test particles that are initially located beyond 28 AU. Because of the slowness of the migration, Neptune＇s mean motion resonances capture test particles very efficiently. Taking into account the stochastic behavior during the planetary migration and for proper parameter values, the resulting concentration of objects in the 3：2 resonance is prominent, while very few objects enter the 2：1 resonance, thus matching the observed Kuiper Belt objects very well. We also find that such a long time-scale migration is favorable for exciting the inclinations of the test particles, because it makes the secular resonance possible to operate during the migration. Our analyses show that the us secular resonance excites the eccentricities of some test particles, so decreasing their perihelion distances, leading to close encounters with Neptune, which can then pump the inclinations up to 20°.
文摘Despite Pluto’s demotion to dwarf planet status,people are still attached to it.Scientists combined observations of Pluto from NASA’s New Horizons probe with observations of comet Churyumov-Gerasimenko from the European Space Agency’s Rosetta probe and found that Pluto’s nitrogen abundance matched the pattern of about a billion comets,which led to the theory that Pluto is made of about a billion comets.Yet they don’t know exactly when or where these comets originated.By studying the origin and orbit of comets,the author of this paper found that the material that condensed Pluto was mainly comets and dust ejected by Neptune,and the Kuiper Belt objects were condensed by material ejected by Neptune toward the outer side of its orbit.
文摘受地球大气影响,使用地基光学望远镜观测角距离较小的双星系统或主卫星系统时往往会出现星象不可分辨的情况.因此,系统光心位置与系统质心位置可能存在一定的偏差.准确地测量太阳系天体系统质心位置可以改进其轨道参数,有助于揭示太阳系的形成与演化.以矮行星Haumea及其亮卫星Hi’iaka的运动为例,仿真系统光心围绕质心扰动的过程,探究视宁度(用星象的半高全宽表示)变化对准确测量光心位置的影响.仿真结果表明,使用二维高斯定心算法测定的系统光心位置随视宁度变化,而修正矩定心算法的定心结果不受视宁度的影响.根据仿真结果,研究能够有效减少视宁度变化对光心位置准确测量影响的定心算法十分必要;同时,新的定心算法还需考虑主星光度变化的影响.使用云南天文台2.4 m望远镜, 1 m望远镜以及紫金山天文台姚安观测站0.8 m望远镜从2022年2月7日至2022年5月25日观测矮行星Haumea系统,得到29晚共463幅CCD图像.新定心算法确定的光心位置与使用二维高斯定心算法的结果相比具有更好的位置拟合效果.此外,还发现亮卫星Hi’iaka在Jet Propulsion Laboratory (JPL)历表与Institut de Mécanique Céleste et de Calcul des éphémérides (IMCCE)历表中的位置存在较大偏差.
基金Supported by the National Natural Science Foundation of Chinasupported by the Natural Science Foundation of China (NSFC+2 种基金Grant Nos. 10833001 and 11073012)the Qing Lan Project (Jiangsu Province)J. Li is also supported by the NSFC (Grant Nos. 1103008 and 11078001)
文摘The population of Neptune Trojans is believed to be bigger than that of Jupiter Trojans and that of asteroids in the main belt, although only eight members of this distant asteroid swarm have been observed up to now. Six leading Neptune Trojans around the Lagrange point L4 discovered earlier have been studied in detail, but two trailing ones found recently around the L5 point, 2004 KV18 and 2008 LC18, have not yet been investigated. We report our investigations on the dynamical behaviors of these two new Neptune Trojans. Our calculations show that the asteroid 2004 KV18 is a temporary Neptune Trojan. Most probably, it was captured into the trailing Trojan cloud no earlier than 2.03 ×105 yr ago, and it will not maintain this position later than 1.65 × 105 yr in the future. Based on the statistics from our orbital simulations, we ar- gue that this object is more like a scattered Kuiper belt object. By contrast, the orbit of 2008 LC18 is much more stable. Among the clone orbits spreading within the orbital uncertainties, a considerable portion of clones may survive on the L5 tadpole orbits for 4 Gyr. The strong dependence of the stability on the semimajor axis and resonant angle suggests that further observations are badly required to constrain the orbit in the stable region. We also discuss the implications of the existence and dynamics of these two trailing Trojans over the history of the solar system.
基金funded partially by BRIN’s research grant Rumah Program AIBDTK 2023。
文摘We intend to study a modified version of the planar Circular Restricted Three-Body Problem(CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified CRTBP.We have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun–Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun–Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter μ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of μ for achieving stability. We remark that the stability range of μ in non-collinear equilibrium points depends on the perturbing parameters. In the context of the Sun–Haumea system, we have found that the non-collinear equilibrium points are stable.
