The Spitzer Space Telescope revolutionized studies of active galactic nuclei (AGNs). Its combined sensitivity and mapping speed at mid-infrared wavelengths revealed a substantial population of highly obscured AGNs. This population implies a higher radiative accretion efficiency, and thus possibly a higher spin, for black holes than indicated by surveys at optical or X-ray wavelengths. The unique mid-infrared spectrographic capability of Spitzer gave important insights into the distribution and nature of the dust surrounding AGNs, enabling the separation of AGN and starburst components, the detection of silicate features in emission from hot dust, and the identification of shocked gas associated with AGN activity. Spitzer’s sensitivity allowed almost complete identification of the host galaxies of samples of AGNs selected in the X-ray and radio. As we look forward to the James Webb Space Telescope, the lessons learned from Spitzer studies will inform observational programmes with new and upcoming infrared facilities.

Spitzer太空望远镜彻底改变了主动星系核（AGN）的研究。它在中红外波长处的灵敏度和测图速度相结合，显示出大量的高度模糊的AGN。与在光学或X射线波长下进行的调查所表明的相比，该总体意味着黑洞具有更高的辐射积聚效率，因此可能具有更高的自旋。Spitzer独特的中红外光谱学能力为AGN周围尘埃的分布和性质提供了重要见解，使AGN和星爆成分得以分离，检测了热尘埃排放中的硅酸盐特征，并确定了与之相关的冲击气体与AGN活动有关。Spitzer的灵敏度几乎可以完全识别在X射线和无线电中选择的AGN样本的宿主星系。