Quasi-Hilda asteroid P/2010 H2 (Vales) underwent a spectacular photometric outburst by ≥7.5 mag (factor of ≥10³) in 2010. Here, we present our optical observations of this event in the four month period from April 20 to August 10. The outburst, starting UT 2010 April 15.70, released dust particles of total cross-section 17,600 km² (albedo 0.1 assumed) and mass ∼1.2נ10⁹ kg, this being about 10⁻⁴ of the mass of the nucleus, taken as a sphere of radius 1.5 km and density 500 kg m⁻³. While the rising phase of the outburst was very steep (brightness doubling time of hours), subsequent fading occurred slowly (fading timescales increasing from weeks to months), as large, low velocity particles drifted away from the nucleus. A simple model of the fading lightcurve indicates that the ejected particles occupied a broad range of sizes, from ∼1 μm to 6 cm, and followed a differential power-law distribution with index 3.60.1 (similar to that in other comets). The fastest particles had speeds ≥210 m s⁻¹, indicating gas-drag acceleration of small grains well coupled to the flow. Low-energy processes known to drive mass loss in active asteroids, including rotational disruption; thermal and desiccation stress cracking; and electrostatic repulsion, cannot generate the high particles speeds measured in P/Vales, and are discounted. Impact origin is unlikely given the short dynamical lifetimes of the quasi-Hildas and the low collision probabilities of these objects. The specific energy of the ejecta is estimated at 220 J kg⁻¹. The outburst follows a series of encounters with Jupiter in the previous century, consistent with the delayed activation of buried supervolatiles (and/or the crystallization of subsurface amorphous ice) by conducted heat following an inward displacement of the perihelion. A potential origin in the debris cloud produced by avalanche is also considered.

准希尔达小行星P / 2010年下半年（瓦莱斯）由≥7.5MAG经历了一个壮观的光度爆发（≥10的因素³，2010年）在这里，我们提出我们这个活动在四个月内的光学观测，从4月20日至八月10.从UT 2010年4月15.70开始爆发，释放了总横截面为17,600 km ²（假定反照率为0.1）且质量约为1.2×10 ⁹ kg的尘埃颗粒，约为核质量的10 ^-4半径为1.5 km且密度为500 kg m ^-3的球体。尽管爆发的上升阶段非常陡峭（亮度增加了几小时），但随后的衰落却发生得很慢（衰落时间从几周增加到几个月），因为大的低速粒子从核中漂移了。衰落光变曲线的一个简单的模型表示该射出的粒子所占的宽范围的尺寸，从〜1 μ m至6厘米，并随后用指数3.60.1（类似于在其它彗星）的差分幂律分布。最快的粒子的速度≥210ms ^-1，表明小颗粒的气阻加速与流动良好耦合。已知会导致活动小行星质量损失的低能量过程，包括旋转破坏；热应力和干燥应力开裂；和静电排斥力，无法产生以P / Vales为单位的高粒子速度，因此被打折。鉴于准希尔达斯的短动态寿命和这些物体的低碰撞概率，撞击起源不太可能。喷射物的比能估计为220 J kg ^-1。爆发是在上个世纪与木星的一系列相遇之后发生的，这与近日点向内移位后的传导热导致埋藏的超挥发物的延迟活化（和/或地下无定形冰的结晶）一致。还考虑了雪崩产生的碎片云的潜在起源。