https://wccftech.com/google-camera-7-2-app-brings-astrophotography-super-res-zoom-to-older-pixel-phones/

A new Google Camera mod has been released which brings Astrophotography and Super Res Zoom to older Pixel phones. Both of these feature are officially available on Pixel 4, but thanks to Google Camera 7.2 mod, these feature can now be used on Pixel 1 and Pixel 2 smartphones.

Since most of the camera features that Google introduces in the latest Pixel phones use machine learning and artificial intelligence, it is possible to port these back to older phones. There might be a performance hit due to slower internals, but more often than not, you can get better results with a 'Gcam mode' than the stock camera app.