发表机构
UCLA; Space Telescope Science Institute（加州大学洛杉矶分校; 太空望远镜科学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用哈勃空间望远镜对活跃小行星Bennu进行高分辨率观测，未发现喷射物质，质量损失率远低于其他活跃小行星，表明许多小行星活动可能低于远程观测阈值，并估算了主带小行星的尘埃产生率。
AI 中文摘要
来自NASA的OSIRIS-REx航天器的测量显示，(101955) Bennu是活跃小行星类的一员。这类天体表现出瞬态的、类似彗星的活动，通常产生粒子轨迹，最好从靠近投影轨道平面的有利位置进行观测。因此，我们于2023年在轨道平面穿越时，使用哈勃空间望远镜对Bennu进行了深度的、高分辨率的观测。我们没有发现喷射物质的证据，并通过对近核表面亮度分布的分析，将质量损失率限制在dM/dt < 0.12 kg/s，而根据未测量到粒子轨迹，限制为dM/dt < 6e-3 kg/s。这些限制比其他活跃小行星中远程测量的质量损失率小一到两个数量级，并提出了一种可能性，即许多或大多数小行星的低活动性可能低于远程观测所提供的普遍阈值。取OSIRIS-REx数据估算的更小的质量损失率，我们计算了特定速率L = 1e-7 kg/km2/s，并将其外推到整个主带小行星群体。我们估计累积尘埃产生率为850/r_min**1/2 [kg/s]，其中r_min是以米为单位的最小小行星半径。对于r_min > 1 m，这不到维持黄道云稳态所需速率的1%到10%。
英文摘要
Measurements from NASA's OSIRIS-REx spacecraft revealed (101955) Bennu as a member of the active asteroid class. These objects exhibit transient, comet-like activity, commonly producing particle trails best observed from a vantage point close to the projected orbit plane. Accordingly, we obtained deep, high resolution observations of Bennu at orbit plane crossing in 2023, using the Hubble Space Telescope. We find no evidence for ejected material, and place model-dependent limits to the mass loss of dM/dt < 0.12 kg/s from an analysis of the near-nucleus surface brightness profiles and dM/dt < 6e-3 kg/s from the absence of a measurable particle trail. These limits are one to two orders of magnitude smaller than rates of mass loss measured remotely in other active asteroids and raise the possibility that low activity in many or most asteroids might fall beneath the prevailing thresholds offered by remote observations. Taking a still smaller mass loss rate estimated from OSIRIS-REx data, we calculate a specific rate L = 1e-7 kg/km2/s and extrapolate to the entire main-belt asteroid population. We estimate a cumulative dust production rate 850/r_min**1/2 [kg/s], where r_min is the minimum asteroid radius in meters. For r_min > 1 m, this is <1% to 10% of the rate needed to sustain the Zodiacal cloud in steady state.
Comments18 pages, 7 figures
