共查询到19条相似文献，搜索用时 140 毫秒
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1992年以来，在海王星外的太阳系发现了近千个小天体，称为Kuiper带天体(KBO)或Edgeworth—Kuiper带天体，其中有一部分偏心率和倾角较大的小天体与海王星之间存在3：2平运动共振，轨道特征类似冥王星，命名为类冥王星，自KBO发现以来，天文学家们进行了多次小天区的搜索，发现了几个质量较大的KBO，通过数值计算，在轨道参数空间发现了两个和冥王星一样同时具有3种共振的区域，在这两个区域里的小天体既避免了海王星的强摄动又不会与冥王星密切交会，轨道非常稳定，因此有可能在其中发现质量较大的类冥王星。 相似文献
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Kuiper带是指太阳系内位于离太阳30－50AU一个区域。1992年该区域陆续发现了一群半径在几十到几百公里的小天体。这些小天体在Kuiper带的分布是极其不均匀的。Kuiper带小天体的发现对人们认识太阳系的形成与演化有重要的意义。本文回顾了近年来国际上在Kuiper带小天体动力演化方面的研究，着重分析了目前国际上几种用以解释其非均匀分布的动力学机制，并提出目前该领域的一些尚未解决的问题。 相似文献
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最近的多普勒观测表明恒星HD 12661周围存在两颗中等偏心率轨道上运行的行星,内行星的最小质量为2．3木星质量,轨道周期为263．6天;外行星的最小质量为1．57木星质量,轨道周期为1444．5天．该系统的稳定性要求两颗行星处在平运动轨道共振．用数值方法研究了该系统形成初期在恒星气体盘作用下的轨道迁移与稳定性,计算了行星在迁移中被平运动共振俘获的概率．发现这两颗行星目前很可能正处在11:2平运动共振边缘,且运动是混沌的,从而澄清了关于系统目前构形的不同说法,并且很可能在系统形成后行星迁移到目前构形时,气体盘几乎消失了． 相似文献
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近地小行星(10302) 1989 ML和(4660) Nereus作为下一代深空探测的候选目标一直备受关注. 在考虑太阳系主要天体的动力学背景下, 通过计算最大Lyapunov指数(MLE)及MEGNO (Mean Exponential Growth factor of Nearby Orbits)指数讨论它们的稳定性. 同时, 对每个小行星, 在其观测误差范围内按多元正态分布各选取1000个克隆粒子, 通过统计分析显示这两个小行星在10万年内可能的运动范围, 给出半长径-偏心率空间中的出现次数分布图, 并统计小行星与地球或其他大行星之间的密近交汇及碰撞的概率. 此外还对这两个小行星的标称轨道进行长期共振、Kozai共振及平运动共振的动力学分析. 综上得出结论, 1989 ML处在平运动共振主导的区域, 发生密近交汇的概率较小, 从而其轨道相对较稳定; 而Nereus处在地球的密近交汇区域, 轨道极不稳定. 相似文献
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目前观测到的海王星特洛伊天体已有17颗并已积累了较为精确的轨道数据,系统分析了这些天体轨道的动力学稳定性.数值结果表明:除去两个寿命短到只有数万年和百万年的临时海王星特洛伊,大部分天体在其轨道根数不确定范围内都可以存活至45亿年.大约有一半的海王星特洛伊在45亿年的时间内离开共振区,而逃离的途径是复杂动力学机制下轨道根数空间内缓慢的扩散.在半人马小行星群中识别并证认了一个新的海王星特洛伊天体2012 UW177,数值模拟表明该天体目前正在围绕海王星L4点的蝌蚪形轨道上运动.该天体大约在23万年前进入当前轨道,且未来将在该轨道停留至少130万年.约54°的倾角使得它的轨道成为最倾斜的轨道,并且使得该天体展现经由拟卫星轨道的复杂有趣的共轨轨道转换. 相似文献
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太阳系的九大行星除水星和冥王星稍有出格外,其他行星的轨道实际上都位于一个平面内。大多数研究天体演化的学者都认为这是由于诸行星是从一个围绕着早期太阳旋转的盘状尘埃云里的物质形成的,太阳本身也是由该云的气体和尘埃凝聚形成的。 相似文献
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以当前太阳系动力学中的重要课题以及研究方法进行讨论，并提出一些看法，课题中主要讨论动力学模型，轨道共振，行星环，混沌和长期演化，近地天体运动，Kupiper带，太阳系中的引力理论，以及其他有关问题。 相似文献
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Kuiper带天体的轨道分布特性 总被引：3，自引：1，他引：2
1992年9月,夏威夷大学的D.Jewitt和加利福尼亚大学的J.Lun发现了海王星外绕太阳运行的第一个小天体1992QB1[1],开创了人类对于海王星外天体的实际观测的研究.近10年的接连不断发现,已经证实了海王星轨道外面存在着一个由大量的环绕太阳运动的小天体组成的环带[2].由于G.P.Kuiper曾在1951年的文章中提出过在冥王星的外边可能存在小天体的问题,因此人们一般把这个环带称为Kuiper带,你这些天体为“KuiperBelt Objects”(KBOs),或从逻辑上称它们为“Trans-NeptunianObjects”(TNOs)[3] 相似文献
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Spencer John Buie Marc Young Leslie Guo Yanping Stern Alan 《Earth, Moon, and Planets》2003,92(1-4):483-491
Development of the New Horizons mission to Pluto and the Kuiper Belt is now fully funded by NASA (Stern and Spencer, this volume). If all goes well, New Horizons will be launched in January 2006, followed by a Jupiter gravity assist in 2007, with Pluto arrival expected in either 2015 or 2016, depending on the launch vehicle chosen. A backup launch date of early 2007, without a Jupiter flyby, would give a Pluto arrival in 2019 or 2020. In either case, a flyby of at least one Kuiper Belt object (KBO) is planned following the Pluto encounter, sometime before the spacecraft reaches a heliocentric distance of 50 AU, in 2021 or 2023 for the 2006 launch, and 2027 or 2029 for the 2007 launch. However, none of the almost 1000 currently-known KBOs will pass close enough to the spacecraft trajectory to be targeted by New Horizons, so the KBO flyby depends on finding a suitable target among the estimated 500,000 KBOs larger than 40 km in diameter. This paper discusses the issues involved in finding one or more KBO targets for New Horizons. The New Horizons team plans its own searches for mission KBOs but will welcome other U.S, or international team who wish to become involved in exchange for mission participation at the KBO. 相似文献
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Fast photometric observations of target stars in the ecliptic are a powerful tool to detect small objects in the Kuiper Belt. The various parameters involved in such observations are described. Meter-sized telescopes are able to detect sub-kilometer KBO (Kuiper Belt Objects). A campaign of research of KBO by stellar occultations, organized at the Pic du Midi Observatory is presented. These observations bring the first constraint on the small end of the size distribution of the KBOs. 相似文献
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Processes relevant to Pluto's atmosphere are discussed,and our current knowledge is summarized, including results of two stellar occultationsby Pluto that were observed in 2002. The question of whether other Kuiper belt objects (KBOs)may have bound atmospheres is considered, and observational indicators for KBO atmospheresare described. The definitive detection of a KBO atmosphere could be established withtargeted stellar-occultation observations. These data can also establish accurate diametersfor these objects and be used to detect possible nearby companions. Strategies for acquiringoccultation data with portable, airborne, and fixed telescopes are evaluated in terms of thenumber of KBO occultations per year that should be observable. For the sample of 29 currentlyknown KBOs with H ≤ 5.2, (radius ≤ 300 km for a geometricalbedo of 0.04), we expect about 4 events per year would yield good results for a (stationary) 6.5-m telescope. A network of portable0.36-m telescopes should be able to observe 6 events per year, and a 2.5-m airborne telescopewould have about 200 annual opportunities to observe KBO occultations. 相似文献
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The first phase of the Caltech Wide Area Sky Survey occurred from lateNovember 2001 through mid-April 2003. We present preliminary resultsfrom this survey which has detected 28 bright Kuiper Belt Objects(KBOs) and 4 Centaurs, 19 of which were discovered in our surveyincluding Quaoar, the largest KBO, as well as 6 of the 10intrinsically brightest KBOs. We have surveyed 5108 square degrees ofthe sky nearest the invariable plane to a limiting red magnitude of20.7. Correcting for the overabundance of objects near the invariableplane, this represents 27% completeness in terms of KBO numbers.Thus, approximately 100 KBOs and Centaurs brighter than mR = 20.7exist, about 3/4 of which remain undiscovered. The bright KBOs areconsistent with the canonical q=4 size distribution, suggesting thatabout ten 1000 km diameter KBOs and about one 2000 km diameter KBOexist. Additionally, we observe only 3 KBOs with low inclination(i < 7 degrees) with 67% of the sky available to these objectssurveyed. This is in sharp contrast with the known KBOs, of whichabout 60% of the ～ 800 observed objects (as of May 2003) have i< 7 degrees. Although we observe at systematically higher invariableplane latitudes than many deeper KBO surveys, such systematic biasescannot fully explain the lack of low inclination objects, ameasurement which is significant at the > 3 σ level. Thissuggests that the bright KBOs have a fundamentally different maximumsize than the fainter KBOs. A better characterization of the surveylimiting magnitude and a more thorough modeling of observational biaseffects of different classes of KBOs will be made in a future work. 相似文献
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Six nights of R-band CCD observations of the classical Kuiper Belt Object (KBO) 20000 Varuna (2000 WR106) were obtained at the Palomar Mountain 60- and 200-in telescopes. The observations were scheduled to take advantage of a particularly favorable apparition which allowed us to sample down to extremely small solar phase angle (α=0.036°). After rotational lightcurve subtraction, we found that the KBO exhibited a strong opposition surge of ∼0.1 mag at phase angles α<0.1°. We modeled our composite solar phase curve of Varuna using both H-G parameterization and Hapke theory and concluded that similar opposition surges may be wide spread among KBOs and that the regolith of Varuna may be significantly more porous than a typical main-belt C-type asteroid. Wide-spread opposition surges lead to higher albedos than derived assuming linear phase behavior: on the whole KBOs may be brighter than previously assumed. 相似文献
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Using the N-body dynamical model that includes the sun, the 8 planets, Pluto, UB313 and massless particles, we simulate the orbital evolution of 551 Kuiper Belt Objects (KBOs) with known parameters. The initial conditions of the simulations are the currently observed orbital parameters. The integration backtracks from now to -10×108 yr. The results show that about 10×108 years ago, more than 1/3 of the presently observed KBOs resided in the region of the present Kuiper main belt, a few were located inside the Neptune orbit, and the rest were beyond 50AU; and that about 4.5×108 years ago, all the objects in the Kuiper main belt exhibited a rather good normal distribution, without so many objects concentrated in the Neptune's 3:2 resonance region, as at present time. 相似文献
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S. Alan Stern 《Icarus》2009,199(2):571-573
In this Note, I present first-order scaling calculations to examine the efficacy of impacts by Kuiper Belt debris in causing regolith exchange between objects in the Pluto system. It is found that ejecta can escape Nix and Hydra with sufficient velocity to reach one another, as well as Charon, and even Pluto. The degree of ejecta exchanged between Nix and Hydra is sufficient to cover these bodies with much more material than is required for photometrically change. In specific, Nix and Hydra may have exchanged as up to 10s of meters of regolith, and may have covered Charon to depths up to 14 cm with their ejecta. Pluto is likely unaffected by most Nix and Hydra ejecta by virtue of a combination of dynamical shielding from Charon and Pluto's own annual atmospheric frost deposition cycle. As a result of ejecta exchange between Nix, Hydra, and Charon, these bodies are expected to evolve their colors, albedos, and other photometric properties to be self similar. These are testable predictions of this model, as is the prediction that Nix and Hydra will have diameters near 50 km, owing to having a Charon-like albedo induced by ejecta exchange. As I discuss, this ejecta exchange process can also be effective in many KBOs and asteroids with satellites, and may be the reason that very many KBO and asteroid satellite systems have like colors. 相似文献
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Three resonances, the 3:2 exterior mean motion resonance with Neptune, Kozai resonance and 1:1 super resonance, are known to govern concurrently the stability of the motion of Pluto. We explore numerically the resonance zones in which the three resonance coexist. There might exist plutinos with relatively large masses in these zones. Considering that Pluto's perturbation is important to the long-term evolution of plutinos, the resonance zone is mainly explored in the mirror region of Pluto, which is a mirror image of the region around Pluto with respect to the invariant plane of the solar system. We find six resonance zones in the mirror region. The orbit elements at the centers of the six zones and the corresponding heliocentric distances, longitudes and latitudes on July 1, 2003 have been computed and listed for the reference of observation. 相似文献
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Bradley E. SchaeferDavid L. Rabinowitz 《Icarus》2002,160(1):52-58
Kuiper belt objects (KBOs) are generally very faint and cannot in practice be monitored with a well-sampled long-term light curve; so our discovery of the bright KBO 2000 EB173 offers an excellent opportunity for synoptic studies. We present a well-sampled photometric time series (77 R and 29 V magnitudes on 78 nights) over a 225-day time span centered on the 2001 opposition. The light curve (corrected to the year 2001 opposition distance) varies from 19.11 to 19.39 mag with a single peak that is smooth, time symmetric, and coincident with opposition. All variations in the light curve are consistent with a linear opposition surge (ROPP=19.083+0.125∗α, where α is the solar phase angle), while any rotational modulation must have a peak-to-peak amplitude of less than 0.097 mag. This is the first measured opposition surge for any KBO (other than Pluto). The V−R color is 0.63±0.02, with no apparent variation with phase at the few percent level. With R=19.11 at opposition, 2000 EB173 remains the brightest known KBO and a prime target for future photometric and spectroscopic studies. 相似文献