Context: Potentially hazardous asteroids (PHA) in Earth-crossing orbits pose a constant threat to life on Earth. Several mitigation methods have been proposed, and the most feasible technique appears to be the disintegration of the impactor and the generation of a fragment cloud by explosive penetrators at interception. However, mitigation analyses tend to neglect the effect of orbital dynamics on the trajectory of fragments.
Aims: We aim to study the effect of orbital dynamics of the impactor's cloud on the number of fragments that hit the Earth, assuming different interception dates. We investigate the effect of self-gravitational cohesion and the axial rotation of the impactor.
Methods: We computed the orbits of 10^5 fragments with a high-precision direct N-body integrator of the eighth order, running on GPUs. We considered orbital perturbations from all large bodies in the Solar System and the self-gravity of the cloud fragments.
Results: Using a series of numerical experiments, we show that orbital shear causes the fragment cloud to adopt the shape of a triaxial ellipsoid. The shape and alignment of the triaxial ellipsoid are strongly modulated by the cloud's orbital trajectory and, hence, the impact cross-section of the cloud with respect to the Earth. Therefore, the number of fragments hitting the Earth is strongly influenced by the orbit of the impactor and the time of interception. A minimum number of impacts occur for a well-defined orientation of the impactor rotational axis, depending on the date of interception.
Conclusions: To minimise the lethal consequences of an PHA's impact, a well-constrained interception timing is necessary. A too-early interception may not be ideal for PHAs in the Apollo or Aten groups. Thus, we find that the best time to intercept PHA is when it is at the pericentre of its orbit.
The dynamically hazardous asteroid 2025 TV$_{10}$. A new co-orbital asteroid of Venus
São Paulo State University (UNESP)（圣保罗州立大学）；Laboratório Interinstitucional de e-Astronomia（跨机构电子天文学实验室）；LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（LIRA，巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，CY塞尔吉巴黎大学，法国国家科学研究中心）
Asteroid impacts pose a major threat to all life on Earth. The age of the dinosaurs was abruptly ended by a 10-km-diameter asteroid. Currently, a nuclear device is the only means of deflecting large Potentially Hazardous Asteroids (PHAs) away from an Earth-impacting trajectory. The Enhanced Kinetic Impactor (EKI) concept is proposed to deflect large PHAs via maneuvering space rocks. First, an unmanned spacecraft is launched to rendezvous with an intermediate Near-Earth Asteroid (NEA). Then, more than one hundred tons of rocks are collected from the NEA as the EKI. The NEA can also be captured …
Composition of Potentially Hazardous Asteroid (214869) 2007 PA8: An H Chondrite from the Outer Asteroid Belt
有潜在危险的小行星是在其接近地球期间进行物理特性鉴定的一个独特机会。这些小行星的距离很近，使它们能够进行采样返回和载人飞行任务，但如果发生碰撞，也可能对地球上的生命构成风险。因此，详细的矿物学分析是规划未来勘探任务和制定适当缓解战略的关键组成部分。在这项研究中，我们提出了近红外光谱（0.7-2.55微米）的PHA（214869）2007 PA 8获得与美国宇航局红外望远镜设施在其接近地球的2012年11月。对这颗小行星的矿物学分析显示，其表面成分与普通的H型陨石一致。特别地，我们发现2007 PA 8的橄榄石和辉石化学分别是Fa 18（Fo 82）和Fs 16。橄榄石-辉石丰度比估计为47%。这一低橄榄石丰度和测量的带参数，接近H4和H5方解石，表明2007年PA 8的母体经历了热变质，然后才被灾难性地破坏。根据组成的亲和力，接近J5：2共振，估计通量的共振对象，我们确定的Koronis家庭是最有可能的源区2007年PA 8。
Large potentially hazardous asteroids (PHAs) are capable of causing a global catastrophe in the event of a planetary collision. Thus, rapid assessment of such an object's physical characteristics is crucial for determining its potential risk scale. We treated the near-Earth asteroid (99942) Apophis as a newly discovered object during its 2020-2021 close-approach as part of a mock planetary defense exercise. The object was detected by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), and data collected by the two active bands (3.4 $μ$m and 4.6 $μ$m) were analyzed using therma…
The asteroid 2014 JO25, considered to be "potentially hazardous" by the Minor Planet Center, was spectroscopically followed during its close-Earth encounter on 19th and 20th of April 2017. The spectra of the asteroid were taken with the low resolution spectrograph (LISA), mounted on the 1.2-m telescope at the Mount Abu Infrared Observatory, India. Coming from a region close to the Hungaria population of asteroids, this asteroid follows a comet-like orbit with a relatively high inclination and large eccentricity. Hence, we carried out optical spectroscopic observations of the asteroid to look f…
We present a fireball detected in the night sky over Kyoto, Japan on UT 2017 April 28 at ${\rm 15^{h}\,58^{m}\,19^{s}}$ by the SonotaCo Network. The absolute visual magnitude is $M_{\rm v}$=$-$4.10$\pm$0.42mag. Luminous light curves obtain a meteoroid mass $m$=29$\pm$1g, corresponding to the size $a_{\rm s}$=2.7$\pm$0.1cm. Orbital similarity assessed by D-criterions (cf. $D_{\rm SH}$=0.0079) has identified a likely parent, the binary near-Earth asteroid (164121) 2003 YT$_1$. The suggested binary formation process is a YORP-driven rotational disintegration (Pravec & Harris 2007). The asynchrono…
By means of a fully connected artificial neural network, we identified asteroids with the potential to impact Earth. The resulting instrument, named the Hazardous Object Identifier (HOI), was trained on the basis of an artificial set of known impactors which were generated by launching objects from Earth's surface and integrating them backward in time. HOI was able to identify 95.25% of the known impactors simulated that were present in the test set as potential impactors. In addition, HOI was able to identify 90.99% of the potentially hazardous objects identified by NASA, without being traine…
Rotation, spectral type, and albedo of the potentially hazardous asteroid (153814) 2001 WN$_{\text 5}$ Prior to the 2028 June close approach
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心，拉格朗日实验室）；Department of Earth and Planetary Science, The University of Tokyo（东京大学地球行星科学系）；Institute of Astronomy, V.N. Karazin Kharkiv National University（哈尔科夫国立大学瓦·尼·卡拉津天体物理研究所）；Astronomical Institute ASCR（捷克科学院天文研究所）
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency（宇宙科学研究所）；Rowan University（罗文大学）；Lunar and Planetary Laboratory, University of Arizona（亚利桑那大学）；Department of Earth and Planetary Sciences, American Museum of Natural History（美国自然历史博物馆）；The University of Tokyo（东京大学）
Astrometric and Photometric Investigations of 2009 WZ104 Near Earth Asteroid
2009年11月25日，美国亚利桑那州莱蒙山天文台的68厘米施密特卡特琳娜巡天望远镜发现了WZ 104小行星。新物体的观测结果得到了Schiaparelli天文台（意大利）60厘米反射镜和Alter Saltzberg天文台（奥地利维也纳）35厘米施密特-卡塞格伦望远镜的证实。这颗小行星被认为是潜在的危险近地小行星。最小轨道相交距离为0.0304 a.e.。自2009年底以来，普尔科沃天文台（俄罗斯）的MTM-500 M 50厘米弯月望远镜和ZA-320 M 32厘米镜面天体照相机继续对2009 WZ 104小行星进行观测。这些观测是在近地天体调查方案的框架内进行的。为调查确定了以下任务：获得天体测量和测光（BVRI波段）系列观测，根据观测数据改进小行星轨道，确定其分类类别和绝对星等，调查其旋转动力学，估计其物理参数。这颗小行星属于小行星群中的Aten。
Fifteen orbital clusters (associations) were identified among ~20000 near Earth asteroids (NEAs). All associations were found with a high statistical reliability using a single linkage cluster analysis algorithm and three orbital similarity functions. The identified groups constitute a small fraction (4.74 %) of the entire sample. Nonetheless they may be hazardous to the Earth and its inhabitants. As it happens with meteoroid streams, every year the Earth comes very close to the orbits of each association. In two cases (2008TC3 and 2017FU102) the distance between the asteroid's and the Earth's…
Spin Parameters and Shape Models of Near-Earth Asteroids (4660) Nereus, (21088) Chelyabinsk, (66146) 1998 TU3, and (297418) 2000 SP43
Instituto Universitario de Ciencias y Tecnologías Espaciales de Asturias (ICTEA), University of Oviedo（阿斯图里亚斯太空科学与技术大学研究所，奥维耶多大学）；Departamento de Matemáticas, Facultad de Ciencias, Universidad de Oviedo（奥维耶多大学理学院数学系）；Departamento de Informática, Facultad de Ciencias, Universidad de Oviedo（奥维耶多大学理学院计算机系）；Instituto de Astrofísica de Canarias (IAC)（加那利群岛天体物理研究所）；Departamento de Astrofísica, Universidad de La Laguna（拉帕尔马大学天体物理学系）；Light Bridges S. L., Observatorio Astronómico del Teide（光桥有限公司，泰德天文台）；Observatorio Isaac Aznar-MPC Z95（艾萨克·阿兹纳尔小行星中心观测站 Z95）；Departamento de Explotación y Prospección de Minas, Universidad de Oviedo（奥维耶多大学矿产开发与勘探系）
Composition of Near-Earth Asteroid 2008 EV5: Potential target for Robotic and Human Exploration
我们在可见光（0.30-0.92微米）和近红外（0.75-2.5微米）波长下观察了潜在危险的小行星（PHA）2008 EV 5，以确定其表面成分。这颗小行星特别令人感兴趣，因为它是两个样本返回任务提案（马可波罗-R和隼鸟-2）和人类探索的潜在目标，因为它的低delta-v交会。2008 EV 5的光谱除了一个0.48微米的弱自旋禁戒Fe 3+吸收带外，基本上没有什么特征。光谱也有一个整体的蓝色斜率。2008年EV 5的最大值仍然不确定，根据热模型，下限为0.05，上限为0.20。Busch等人（2011年）估计的0.12与我们的热建模结果一致。2008年EV 5的基因组和组成也与C型分类学分类一致（Somers等人，2008年）。最佳光谱匹配是与类似于Orgueil的Cl碳质方解石，其也具有弱的0.48微米特征和整体蓝色斜率。这个0.48微米的特征也可以在磁铁矿的光谱中看到。CI卫星的最大值是我们对2008年EV 5最大值的估计范围的下限。
Near-Earth asteroid (410777) 2009 FD is a potentially hazardous asteroid with potential impacts on Earth at the end of the 22nd century. The astrometry collected during the 2019 apparition provides information on the trajectory of (410777) by constraining the Yarkovsky effect, which is the main source of uncertainty for future predictions, and informing the impact hazard assessment. We included the Yarkovsky effect in the force model and estimated its magnitude from the fit to the (410777) optical and radar astrometric data. We performed the (410777) hazard assessment over 200 years by using t…
The surfaces of airless bodies such as asteroids are exposed to many phenomena that can alter their physical properties. Bennu, the target of the OSIRIS-REx mission, has demonstrated how complex the surface of a small body can be. In 2019 November, the potentially hazardous asteroid 2015 JD1 experienced a close approach of 0.0331 au from the Earth. We present results of the physical characterization of 2015 JD1 based on ground-based radar, spectroscopy, and photometric observations acquired during 2019 November. Radar polarimetry measurements from the Arecibo Observatory indicate a morphologic…
Thermophysical characterization of the potentially hazardous near-Earth object 2024 YR4
Max-Planck-Institut für extraterrestrische Physik (MPE)（德国马克斯·普朗克地外物理学研究所）；University of Helsinki（赫尔辛基大学）；Massachusetts Institute of Technology（麻省理工学院）；Space Telescope Science Institute（太空望远镜科学研究所）；Johns Hopkins University Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；Astronomical Institute, Academy of Sciences of the Czech Republic（捷克科学院天文研究所）；ESA NEO Coordination Centre（欧洲空间局近地天体协调中心）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
Thermal Infrared Observations of Asteroid (99942) Apophis with Herschel
小行星阿波菲斯（99942）是一颗具有潜在危险的小行星。我们用赫歇尔空间天文台的PACS仪器在70、100和160微米处对这颗小行星进行了远红外观测。这些照片是在2013年1月和3月的两个时间点，在一次近距离接触地球时拍摄的。这些第一次对阿波菲斯的热测量是在反对派之前和之后以类似的相位角进行的。我们进行了详细的热物理模型分析，通过使用自旋和形状模型最近来自应用2周期傅立叶级数方法，以及校准光度观测的大样本。我们发现，翻滚的小行星阿波菲斯有一个细长的形状，平均直径为375 $^{+14}_{-10}$米（等体积球体）和几何V带的半径为0.30 $^{+0.05}_{-0.06}$。我们发现热惯性在250-800 Jm $^{-2}$ s $^{-0.5}$ K $^{-1}$范围内（最佳解为600 Jm $^{-2}$ s $^{-0.5}$ K $^{-1}$），这可以用低传导性细风化层与表面高热惯性的较大岩石和巨石的混合物来解释。热惯性和其他与（25143）丝川的相似之处表明阿波菲斯可能也有一个碎石堆结构。如果我们结合新的尺寸值与丝川式的密度和孔隙度的假设，我们估计的质量在4.4和6.2 10 $^{10}$公斤，这是超过2-3倍比以前的估计。我们预计，新得出的属性将影响情景研究和影响阿波菲斯的长期轨道预测。
This work presents a new parametrisation suitable for parameter-space studies of heliocentric Earth-impacting orbits. Originally motivated by the issue of potentially hazardous asteroids (PHAs) and the mitigation of such a risk, we show that the simultaneous analysis of all the conceivable impacting elliptical orbits is greatly facilitated by the use of a parametrisation that involves only the true anomaly at impact, the eccentricity and the inclination. While the new parametrisation is presented from an explicit planetary-defence perspective, it is general enough to be useful in analogous stu…
We are conducting a survey using twilight time on the Dark Energy Camera with the Blanco 4m telescope in Chile to look for objects interior to Earth's and Venus' orbits. To date we have discovered two rare Atira/Apohele asteroids, 2021 LJ4 and 2021 PH27, which have orbits completely interior to Earth's orbit. We also discovered one new Apollo type Near Earth Object (NEO) that crosses Earth's orbit, 2022 AP7. Two of the discoveries likely have diameters greater than 1 km. 2022 AP7 is likely the largest Potentially Hazardous Asteroid (PHA) discovered in about eight years. To date we have covered…
The population of near-Earth asteroids (NEAs) shows a large variety of objects in terms of physical and dynamical properties. They are subject to planetary encounters and to strong solar wind and radiation effects. Their study is also motivated by practical reasons regarding space exploration and long-term probability of impact with the Earth. We aim to spectrally characterize a significant sample of NEAs with sizes in the range of $\sim$0.25 - 5.5 km (categorized as large), and search for connections between their spectral types and the orbital parameters. Optical spectra of NEAs were obtaine…
We present an approach to estimate an upper bound for the impact probability of a potentially hazardous asteroid when part of the force model depends on unknown parameters whose statistical distribution needs to be assumed. As case study we consider Apophis' risk assessment for the 2036 and 2068 keyholes based on information available as of 2013. Within the framework of epistemic uncertainties, under the independence and non-correlation assumption, we assign parametric families of distributions to the physical properties of Apophis that define the Yarkovsky perturbation and in turn the future …
In the framework of the planar and circular restricted three-body problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a non zero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term "qua…
Overview of Hayabusa2 extended mission's flyby of Near-Earth Asteroid (98943) Torifune
Georgia Institute of Technology（佐治亚理工学院）；Japanese Aerospace Exploration Agency（日本宇宙航空研究开发机构）；University of Aizu（会津大学）；Hokkaido University（北海道大学）；National Institute of Advanced Industrial Science and Technology（产业技术综合研究所）；LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris-Cité, CY Cergy Paris Université, CNRS（巴黎天文台LIRA实验室，PSL大学，索邦大学，巴黎西岱大学，CY塞尔吉巴黎大学，法国国家科学研究中心）；Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；University of La Laguna（拉古纳大学）；University of Tokyo（东京大学）
Context. The discovery and tracking of 2018 LA marks only the third instance in history that the parent body of a fireball has been identified before its eventual disintegration in our atmosphere. The subsequent recovery of meteorites from 2018 LA was only the second time materials from outer space that reached the ground could be linked with certitude to a particular minor body. However, meteoroids like 2018 LA and its forerunners, 2008 TC3 and 2014 AA, are perhaps fragments of larger members of the near-Earth object (NEO) population. As the processes leading to the production of such fragmen…
