Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (r_g ≡ GM/c²) scales in nearby sources¹. Centaurus A is the closest radio-loud source to Earth². It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations³, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 r_g scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow⁴ should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses^5,6.

在毫米波长下对活动星系核的超长基线干涉测量 (VLBI) 观测能够揭示河外射电射流的发射和初始准直区域，低至 10-100 引力半径 ( r _g  ≡  G M / c ² )附近来源的规模¹。半人马座 A 是离地球^{2最近的无线电响亮源}. 它弥合了 Messier 87 中的超大质量黑洞 (SMBH) 与我们的银河系中心之间的质量和吸积率差距。然而，迄今为止，-43° 的大南偏角阻止了半人马座 A 的 VLBI 成像，其波长低于 1 厘米。在这里，我们展示了源的毫米 VLBI 图像，这是我们使用事件视界望远镜在 228 GHz 获得的。与之前的观测³相比，我们以高出 10 倍的频率和 16 倍的分辨率对半人马座 A 喷流进行成像，从而探测亚光日结构。我们揭示了一个高度准直的、不对称边缘增亮的喷气机以及较暗的反喷气机。我们发现半人马座 A 的源结构类似于 Messier 87 中约 500  r _{g上的喷流}规模非常好。此外，我们确定了半人马座 A 的 SMBH 相对于其在 1.3 毫米波长处解析的喷流核心的位置，并得出结论，在太赫兹频率下应该可以看到源的事件视界阴影^{4 。}这个位置进一步支持了黑洞在广泛的质量范围内的普遍尺度不变性^5,6。