The nuclear disk is a dense stellar structure at the centre of the Milky Way, with a radius of ~150 pc (ref. ¹). It has been a place of intense star formation in the past several tens of millions of years^1,2,3, but its overall formation history has remained unknown². Here, we report that the bulk of its stars formed at least 8 Gyr ago. After a long period of quiescence, a starburst event followed about 1 Gyr ago that formed roughly 5% of its mass within ~100 Myr, in what may arguably have been one of the most energetic events in the history of the Milky Way. Star formation continued subsequently on a lower level, creating a few per cent of the stellar mass in the past ~500 Myr, with an increased rate up to ~30 Myr ago. Our findings contradict the previously accepted paradigm of quasi-continuous star formation at the Galactic Centre⁴. The long quiescent phase agrees with the overall quiescent history of the Milky Way^2,5 and suggests that our Galaxy’s bar may not have existed until recently, or that gas transport through the bar was extremely inefficient during a long stretch of the Milky Way’s life. Consequently, the central black hole may have acquired most of its mass already in the early days of the Milky Way.

核盘是银河系中心的密集恒星结构，半径约为150 pc（参考文献¹）。在过去的几千万年中，它一直是强烈恒星形成的地方^1,2,3，但其整体形成历史仍然未知²。在这里，我们报告说，它的大部分恒星至少在8个Gyr之前形成。经过长时间的静止，大约在1 Gyr之前发生了一次星爆事件，在约100 Myr内约占其质量的5％，这可能是银河系历史上最活跃的事件之一。随后恒星形成继续处于较低水平，在过去的〜500 Myr中形成了恒星质量的百分之几，直到〜30 Myr才增加了恒星质量。我们的发现与银河系中心⁴先前接受的准连续恒星形成范式相矛盾。较长的静止阶段与银河系的整体静止历史相吻合^2,5并暗示我们的银河系可能直到最近才消失，或者在银河系生命的漫长过程中，通过该系的气体传输效率极低。因此，中央黑洞可能已经在银河系的初期就已经吸收了大部分质量。