Data from: A Saturn-mass free-floating-planet event

A population of free-floating planets is known from gravitational
microlensing surveys. None of those planets have a directly measured mass,
due to a degeneracy with the distance, though the population statistics
indicate that many are less massive than Jupiter. We report a microlensing
event, KMT-2024-BLG-0792/OGLE-2024-BLG-0516, which was observed from both
ground- and space-based telescopes. This breaks the mass-distance
degeneracy; we determine that the event was caused by a planet with
0.219+0.075-0.046 Jupiter masses, which is either gravitationally
unbound or on a very wide orbit. By comparing to the statistical
properties of other observed microlensing events and predictions from
simulations, we infer that this object likely formed in a protoplanetary
disk, not in isolation like a brown dwarf. Dynamical processes then
ejected it from its birth place, producing a free-floating object.

引力微透镜（gravitational microlensing）巡天已发现一批自由漂浮行星（free-floating planets）群体。由于质量与距离存在简并效应，此类行星均无法直接测得其质量；不过群体统计数据显示，其中多数行星的质量小于木星质量。本研究报道了一个由地面与空间望远镜联合观测到的微透镜事件KMT-2024-BLG-0792/OGLE-2024-BLG-0516。该观测突破了质量-距离简并（mass-distance degeneracy）的限制；经测定，此次事件由质量为0.219+0.075-0.046倍木星质量的行星引发，该行星要么不受引力束缚，要么处于极宽轨道上。通过与其他已观测微透镜事件的统计特性及模拟预测结果进行对比，我们推断该天体大概率形成于原行星盘（protoplanetary disk）之中，而非如褐矮星（brown dwarf）般孤立形成。随后通过动力学过程，该天体被从其诞生地抛出，最终成为自由漂浮天体。