OBSERVATIONAL DETECTIONS OF THE ASTEROIDAL YORP EFFECT

小行星约普效应的观测探测

• 批准号: ST/H002553/1
• 负责人: Stephen Lowry
• 金额: $ 40.17万
• 依托单位: University of Kent
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FH002553%2F1
• 关键词: OBSERVATIONAL; DETECTIONS; ASTEROIDAL; YORP; EFFECT

[1] Observational detections of the asteroidal YORP effect: The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is a torque due to both incident solar radiation pressure and the recoil effect from the anisotropic emission of thermal photons (or light particles) on small bodies in the solar system. By analogy, if one throws a ball forward then there is a slight recoil in the opposite direction. The same is true for photons as they leave the surface of an asteroid. The force is minuscule but if summed up over the entire surface, and with countless photons striking it at any given moment, then the effect becomes significant. YORP can modify how fast asteroids spin and the orientation of their spin-axis. YORP-induced torques are very small and can take million of years to reduce the spin rate of a km-size asteroid by 50%. YORP is of fundamental importance to solar system astronomers as it can explain many observed phenomena in asteroidal science. For example it can lead to the ejection of asteroids from the main asteroid belt into near-Earth space. It is also instrumental in the formation of binary asteroids. The sun provides an endless supply of photonic fuel that is perpetually driving the physical condition of some small asteroidal bodies. Despite its importance there have been only a few cases where the YORP effect has been seen in action, due to the difficulties in measuring the effect. Our core aim is to achieve additional YORP detections on a carefully selected sample of other small asteroids to further understand this important process. The study will provide theoreticians with actual measurements to calibrate their calculations. By carefully monitoring small near-Earth asteroids using large telescopes we can look for progressive and coherent small changes in the time it takes to make one full revolution on its spin-axis (on the order of millisecond per year!). We then determine a 3-D shape model for the asteroid and calculate how strong the effect is likely to be for that asteroid, for comparison with that observed. This will add further robustness to our conclusions. The first direct observational detection of the YORP effect was achieved by the PI and colleagues, demonstrating that our techniques and overall approach works. [2] Rosetta In-situ Imaging of Asteroid Steins: A YORP-Evolved Asteroid? Fly bys of asteroids by spacecraft are very rare and the images obtained from them are scientifically invaluable, as they provide surface and shape details that can never be revealed from Earth. ESA's Rosetta spacecraft completed a fly by of asteroid Steins in September 2008. The images sent back to Earth show that the shape of asteroid Steins has at some point in its history been strongly modified by the YORP effect. This is incredibly fortuitous as it may be the only opportunity in our lifetime to study this new class of asteroid up close, and so presents a unique opportunity to advance our understanding of the YORP effect. Using the detailed shape model determined from the spacecraft imaging data we will determine how strong the YORP effect is likely to be on Steins. We will explore the orbital and spin-state histories using state-of-the-art computational techniques, to explore all likely evolutionary scenarios that this asteroid has experienced to lead to this distinctive shape. We can even go one step further and search for signs that material has shifted across the surface, distorting crater features, another potential manifestation of YORP. These are just some of the questions that we have the opportunity to address. And finally we wish to continue to monitor Steins from Earth-based telescopes to see if the effect can actually be observed in action, to further refine our conclusions. We already have a wealth of telescope data available from our pre-fly-by preparations.

[1]小行星YORP效应的观测探测：Yarkovsky-O‘Keefe-Radzievskii-Paddack(YORP)效应是由于入射太阳辐射压力和热光子(或光粒子)对太阳系小天体的各向异性发射的反冲效应所产生的扭矩。以此类推，如果一个人向前抛一个球，那么在相反的方向上就会有一个轻微的后座力。当光子离开小行星表面时，情况也是如此。力是微小的，但如果把整个表面的力加起来，在任何给定的时刻都有无数的光子击中它，那么这种影响就会变得非常显著。YORP可以改变小行星的自转速度和自旋轴的方向。YORP引起的扭矩非常小，可能需要数百万年的时间才能将一颗千米大小的小行星的自转速度降低50%。YORP对于太阳系天文学家来说至关重要，因为它可以解释小行星科学中的许多观察到的现象。例如，它可能导致小行星从主小行星带弹射到近地空间。它在双星小行星的形成过程中也起到了重要作用。太阳提供了无穷无尽的光子燃料，这种燃料一直在推动一些小型小行星的物理条件。尽管YORP效应很重要，但由于难以衡量其影响，只有少数几个案例显示出了YORP效应。我们的核心目标是在精心挑选的其他小行星样本上实现更多的YORP探测，以进一步了解这一重要过程。这项研究将为理论家提供实际测量数据，以校准他们的计算。通过使用大型望远镜仔细监测小型近地小行星，我们可以寻找围绕其自转轴旋转一周所需时间的渐进和连贯的小变化(大约每年毫秒！)。然后我们确定了小行星的三维形状模型，并计算出小行星可能受到的影响有多大，以便与观测到的小行星进行比较。这将进一步增强我们的结论的可靠性。PI和他的同事首次实现了对YORP效应的直接观测检测，证明了我们的技术和整体方法是有效的。[2]小行星Steins的Rosetta原位成像：YORP进化的小行星？航天器飞过小行星的情况非常罕见，从这些小行星上获得的图像具有无价的科学价值，因为它们提供了地球上永远不可能揭示的表面和形状细节。2008年9月，欧空局的Rosetta航天器完成了对小行星Steins的飞越。传回地球的图像显示，小行星斯坦斯的形状在其历史上的某个时候曾受到YORP效应的强烈修改。这是令人难以置信的偶然，因为这可能是我们有生之年唯一近距离研究这类新小行星的机会，因此为我们提供了一个独特的机会来推进我们对YORP效应的理解。使用从航天器成像数据确定的详细形状模型，我们将确定YORP效应对Steins可能有多大。我们将使用最先进的计算技术探索轨道和自旋状态的历史，以探索这颗小行星产生这种独特形状所经历的所有可能的进化情景。我们甚至可以更进一步，寻找物质在表面移动的迹象，扭曲了陨石坑的特征，这是YORP的另一个潜在表现。这些只是我们有机会解决的一些问题。最后，我们希望继续从地球上的望远镜监测斯坦，看看这种影响是否真的可以在行动中观察到，以进一步完善我们的结论。我们已经有了丰富的望远镜数据，可以从我们的飞行前准备中获得。

项目成果

Pre-perihelion activity of comet 67P/Churyumov-Gerasimenko

67P/Churyumov-Gerasimenko 彗星近日点前的活动

• DOI: 10.1051/0004-6361/201424186
• 发表时间: 2014
• 期刊: Astronomy & Astrophysics
• 影响因子: 6.5
• 作者: Guilbert-Lepoutre A

A thermophysical analysis of the (1862) Apollo Yarkovsky and YORP effects

(1862) Apollo Yarkovsky 和 ​​YORP 效应的热物理分析

• DOI: 10.1051/0004-6361/201321659
• 发表时间: 2013
• 期刊: Astronomy & Astrophysics
• 影响因子: 6.5
• 作者: Rozitis B

The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up

• DOI: 10.1051/0004-6361/201322602
• 发表时间: 2014-02
• 期刊: Astronomy and Astrophysics
• 影响因子: 6.5
• 作者: S. Lowry;P. Weissman;S. Duddy;B. Rozitis;A. Fitzsimmons;S. Green;M. Hicks;C. Snodgrass;S. Wolters;S. Chesley;J. Pittichová;P. V. Oers

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

使用罗塞塔上的 OSIRIS 相机进行进近观测所得的 67P/Churyumov-Gerasimenko 的旋转状态

• DOI: 10.1051/0004-6361/201424590
• 发表时间: 2014
• 期刊: Astronomy & Astrophysics
• 影响因子: 6.5
• 作者: Mottola S

A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2.

2009 年的一次碰撞是小行星 P/2010 A2 碎片轨迹的起源。

• DOI: 10.1038/nature09453
• 发表时间: 2010
• 期刊: Nature
• 影响因子: 64.8
• 作者: Snodgrass C