When the light from a distant object passes very near to a foreground galaxy or cluster, gravitational lensing can cause it to appear as multiple images on the sky¹. If the source is variable, it can be used to constrain the cosmic expansion rate² and dark energy models³. Achieving these cosmological goals requires many lensed transients with precise time-delay measurements⁴. Lensed supernovae are attractive for this purpose because they have relatively simple photometric behaviour, with well-understood light curve shapes and colours—in contrast to the stochastic variation of quasars. Here we report the discovery of a multiply imaged supernova, AT 2016jka (‘SN Requiem’). It appeared in an evolved galaxy at redshift 1.95, gravitationally lensed by a foreground galaxy cluster⁵. It is probably a type Ia supernova—the explosion of a low-mass stellar remnant, whose light curve can be used to measure cosmic distances. In archival Hubble Space Telescope imaging, three lensed images of the supernova are detected with relative time delays of <200 d. We predict that a fourth image will appear close to the cluster core in the year 2037 ± 2. Observation of the fourth image could provide a time-delay precision of ~7 d, <1% of the extraordinary 20 yr baseline. The supernova classification and the predicted reappearance time could be improved with further lens modelling and a comprehensive analysis of systematic uncertainties.

当来自远处物体的光非常接近前景星系或星团时，引力透镜会导致它在天空中显示为多个图像¹。如果源是可变的，它可以用来约束宇宙膨胀率²和暗能量模型³。实现这些宇宙学目标需要许多具有精确时延测量的透镜瞬变⁴. 带透镜的超新星对这个目的很有吸引力，因为它们具有相对简单的光度行为，具有易于理解的光曲线形状和颜色——与类星体的随机变化形成鲜明对比。在这里，我们报告发现了一颗多重成像的超新星，AT 2016jka（'SN Requiem'）。它出现在红移 1.95 的演化星系中，由前景星系团^{5引力透镜}. 它可能是 Ia 型超新星——低质量恒星残骸的爆炸，其光变曲线可用于测量宇宙距离。在档案哈勃太空望远镜成像中，检测到超新星的三个镜头图像，相对时间延迟<200 d。我们预测第四张图像将在 2037 ± 2 年出现在星团核心附近。第四张图像的观察可以提供约 7 天的时间延迟精度，<1% 的非凡 20 年基线。通过进一步的透镜建模和对系统不确定性的综合分析，可以改进超新星分类和预测的重现时间。