And so the call went out that the Princess Celestia, beloved sole ruler of Equestria, wished to conduct the most thorough stellar mapping of the sky ever attempted. Ponies whose talents and cutie marks had led to them becoming the greatest minds in the field of Astronomy were called to Canterlot for a grand project that would take years to complete. In under a decade, the city became the leading hub of research into the movement of the Heavens, and although the need for such a thing baffled the common pony, (For why would the very being that controlled the night sky for nearly a thousand years need it studied?) any who witnessed their Princess on a visit to Canterlot's great observatory could sense how deeply the Princess cared for this work.

And as the ponies conducting the studies collaborated and advanced their field, more deep connections were made, spilling over into private hours and personal lives...

This one is just an exploration of my own headcanon about Twilight's parents meeting thanks to Celestia needing to investigate the prophecy involving her sister's escape. It's been in the works for a while.