I'm using an image from https://fermi.gsfc.nasa.gov/science/eteu/agn/ on the Unified Model of AGNs, and I've captioned it
The AGN unified model, showing the BLR and NLR, as well as different types based on the observational angle. Credit: Fermi and NASA: https://fermi.gsfc.nasa.gov/science/eteu/agn/
As far as I can see, the image is not from an original paper. Is this an appropriate way to cite the website? What's the best way to include a citation for an image from a website?