I was surprised to see, with unaided eyes, a rocket like object in the skies on Dec 25, 2021 (Indian time) around the same time as JWST launch. My coordinates were approximately
What surprised me more was I was able to see exhaust gases venting out and a clearly visible plume. There are some twitter post too enquiring about the same.
A recent APOD post has this beautiful picture taken from Thailand indicating Ariane's upper stage is visible quite vividly post engine cutoff.
What is the reason for the venting out of the exhaust plume from Ariane's upper stage post engine cut off?