New Horizons Venetia Burney Student Dust Counter Observes Higher than Expected Fluxes Approaching 60 au

The NASA New Horizons Venetia Burney Student Dust Counter (SDC) measures dust particle impacts along the spacecraft’s flight path for grains with mass ≥10−12 g, mapping out their spatial density distribution. We present the latest SDC dust density, size distribution, and flux measurements through 55 au and compare them to numerical model predictions. Kuiper Belt objects (KBOs) are thought to be the dominant source of interplanetary dust particles in the outer solar system due to both collisions between KBOs and their continual bombardment by interstellar dust particles. Continued measurements through 55 au show higher than model-predicted dust fluxes as New Horizons approaches the putative outer edge of the Kuiper Belt (KB). We discuss potential explanations for the growing deviation: radiation pressure stretches the dust distribution to further heliocentric distances than its parent body distribution; icy dust grains undergo photosputtering that rapidly increases their response to radiation pressure forces and pushes them further away from the Sun; and the distribution of KBOs may extend much further than existing observations suggest. Ongoing SDC measurements at even larger heliocentric distances will continue to constrain the contributions of dust production in the KB. Continued SDC measurements remain crucial for understanding the Kuiper Belt and the interpretation of dust disks around other stars.

美国国家航空航天局（NASA）的“新视野号”上的维妮蒂娅·伯尼学生尘埃计数器（SDC）对沿航天器飞行路径、质量≥10⁻¹²克的尘埃粒子撞击进行测量，绘制出它们的空间密度分布。我们展示了截至55天文单位的最新SDC尘埃密度、尺寸分布和通量测量结果，并将它们与数值模型预测进行了比较。柯伊伯带天体（KBOs）被认为是外太阳系行星际尘埃粒子的主要来源，这是因为KBOs之间的碰撞以及它们不断受到星际尘埃粒子的轰击。在到达55天文单位的持续测量显示，随着“新视野号”接近柯伊伯带（KB）假定的外边缘，尘埃通量高于模型预测值。我们对这种不断增大的偏差进行了可能的解释讨论：辐射压力使尘埃分布延伸到比其母体分布更远的日心距离；冰质尘埃颗粒经历光致溅射，这使其对辐射压力的响应迅速增强，并将它们推离太阳更远；并且KBOs的分布可能比现有观测所表明的要延伸得远得多。在更大日心距离上正在进行的SDC测量将继续对柯伊伯带中尘埃产生的贡献加以限制。持续的SDC测量对于理解柯伊伯带以及解释其他恒星周围的尘埃盘仍然至关重要。