标题： 哈勃空间望远镜对星际闯入者3I/ATLAS的观测 显示英文标题

标题： Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS

摘要： 我们展示了对第三颗已知的星际闯入者3I/ATLAS的高角分辨率观测结果，来自哈勃空间望远镜。 该天体在近日点前3.8天文单位明显活跃，显示出从核的面向太阳的热侧释放出尘埃，并有一个弱的、受辐射压力吹动的尾巴远离太阳。 我们应用一个简单的模型来估算尘埃的质量损失率，即dM/dt = 6 sqrt(a) kg/s，其中a是以微米为单位的平均粒子大小。 当1 < a < 100时，我们推断dM/dt = 6到60 kg/s。 对内晕表面亮度分布的拟合将核的有效半径限制为r < 2.8公里，假设其几何反照率为0.04。 相反，如果其晕由二氧化碳升华提供，则核的半径不能小于0.16公里，如果导致质量损失的分子挥发性较低，则核必须更大。 显示英文摘要

摘要： We present high angular resolution observations of the third known interstellar interloper, 3I/ATLAS, from the Hubble Space Telescope. The object is clearly active at 3.8 au pre-perihelion, showing dust emitted from the hot Sun-facing side of the nucleus and a weak, radiation pressure swept tail away from the Sun. We apply a simple model to estimate the mass loss rate in dust as dM/dt = 6 sqrt(a) kg/s, where a is the mean particle size in microns. With 1 < a < 100, we infer dM/dt = 6 to 60 kg/s. A fit to the surface brightness distribution of the inner coma limits the effective radius of the nucleus to be r < 2.8 km, assuming red geometric albedo 0.04. Conversely, the nucleus cannot be smaller than 0.16 km in radius if its coma is supplied by sublimation of carbon monoxide, and must be larger if a less volatile molecule drives the mass loss.