Relativistic jets are thought to play a crucial role in the formation and evolution of massive galaxies and supermassive black holes. Blazars, which are quasars with jets aligned along our line of sight, provide insights into the jetted population and have been observed up to redshifts of z = 6.1. Here, we report the discovery and multi-wavelength characterization of the blazar VLASS J041009.05−013919.88 at z = 7 (age of the Universe ~750 Myr), which is powered by a ~7 × 10⁸ M_⊙ black hole. The presence of this high-redshift blazar implies a large population of similar but unaligned jetted sources in the early Universe. Our findings suggest two possible scenarios. In one, the jet in J0410−0139 is intrinsically low power but appears highly luminous due to relativistic beaming, suggesting that most ultraviolet-bright quasars at this redshift host jets. Alternatively, if J0410−0139 represents an intrinsically powerful radio source, there should be hundreds to thousands of radio-quiet quasars at z ≈ 7 with properties like those of J0410−0139, a prediction in tension with observed quasar densities based on their ultraviolet luminosity function. These results support the hypothesis that the rapid growth of black holes in the early Universe may be driven by jet-enhanced or obscured super-Eddington accretion, potentially playing a key role in forming massive black holes during the epoch of reionization.

相对论喷流被认为在大质量星系和超大质量黑洞的形成和演化中起着至关重要的作用。Blazars 是类星体，喷流沿着我们的视线对齐，提供了对喷流种群的见解，并且已被观测到高达 z = 6.1 的红移。在这里，我们报告了在 z = 7（宇宙年龄 ~750 Myr）处 blazar VLASS J041009.05−013919.88 的发现和多波长表征，它由 ~7 × 10⁸M_⊙ 黑洞提供动力。这种高红移 blazar 的存在意味着早期宇宙中存在大量相似但未对齐的喷流源。我们的研究结果表明了两种可能的情况。在一个模型中，J0410-0139 中的喷流本质上是低功率的，但由于相对论光束而显得非常明亮，这表明这个红移宿主上的大多数紫外亮类星体都是喷流。或者，如果 J0410−0139 代表一个本质强大的射电源，那么在 z ≈ 7 处应该有成百上千个无线电安静的类星体，它们具有类似于 J0410−0139 的特性，这是根据类星体的紫外线光度函数对观测到的类星体密度的张力预测。这些结果支持了这样一个假设，即早期宇宙中黑洞的快速增长可能是由喷流增强或遮蔽的超级爱丁顿吸积驱动的，可能在再电离时代形成大质量黑洞中发挥关键作用。