It is commonly believed that our own Milky Way is on a collision course with the neighbouring Andromeda galaxy. As a result of their merger, predicted in around 5 billion years, the two large spiral galaxies that define the present Local Group would form a new elliptical galaxy. Here we consider the latest and most accurate observations by the Gaia and Hubble space telescopes, along with recent consensus mass estimates, to derive possible future scenarios and identify the main sources of uncertainty in the evolution of the Local Group over the next 10 billion years. We found that the next most massive Local Group member galaxies—namely, M33 and the Large Magellanic Cloud—distinctly and radically affect the Milky Way–Andromeda orbit. Although including M33 increases the merger probability, the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way–Andromeda orbit and makes their merger less probable. In the full system, we found that uncertainties in the present positions, motions and masses of all galaxies leave room for drastically different outcomes and a probability of close to 50% that there will be no Milky Way–Andromeda merger during the next 10 billion years. Based on the best available data, the fate of our Galaxy is still completely open.

人们普遍认为，我们自己的银河系正在与邻近的仙女座星系发生碰撞。由于它们的合并，据预测，在大约 50 亿年后，定义当前本星系群的两个大型螺旋星系将形成一个新的椭圆星系。在这里，我们考虑了盖亚和哈勃太空望远镜最新、最准确的观测结果，以及最近的共识质量估计，以得出可能的未来情景，并确定未来 100 亿年本星系群演化不确定性的主要来源。我们发现，下一个质量最大的本星系群成员星系——即 M33 和大麦哲伦星云——明显而根本地影响着银河系-仙女座大星系的轨道。尽管包括 M33 增加了合并概率，但大麦哲伦星云的轨道垂直于银河系-仙女座轨道，使它们合并的可能性较小。在整个系统中，我们发现所有星系当前位置、运动和质量的不确定性为截然不同的结果留下了空间，并且有接近 50% 的可能性在未来 100 亿年内不会发生银河系-仙女座大系合并。根据现有的最佳数据，我们银河系的命运仍然完全开放。