I guess what he is talking about is that you linked the image (https://apod.nasa.gov/apod/ image /2602/PIA20522enceladus .jpg ), but not the actual blog post (https://apod.nasa.gov/apod/ap260207.html (be sure not to include /fap/ in the link)) that include the textual information.

I am not sure if the image will show when adding the blog post as a link (instead of the image link), but when using the image link it is nice to add the blog post seperately. I think the blog post would be more valuable than the individual organisations underneath.

I commend you are adding sources! Thank you :)