Thursday marks what would have been astronomer Carl Sagan’s 83rd birthday. The icon of popular science and turtleneck sweaters alike is most known for his contributions to astronomy, astrobiology, and, of course, for hosting the much-beloved Cosmos series.

Though Sagan died in 1996, his scientific legacy lives on in his myriad writings, including the famous Pale Blue Dot. While scientists and artists have written so many touching tributes to the late astronomer over the years, none is more heart-wrenchingly beautiful than the one penned by his wife, author and producer Ann Druyan.

Back in 2003, Druyan reflected on her nearly 20-year relationship with Sagan for The Skeptical Inquirer. The couple met at screenwriter Nora Ephron’s home in New York City in 1974, and were married from 1981 until his death from pneumonia 15 years later.

No matter what you do — or don’t — believe about the afterlife, Druyan’s note is irrefutably one of the most poignant letters ever written about the special peculiarity of love. Here’s an excerpt via Goodreads — but fair warning, get the tissues ready:

When my husband died, because he was so famous and known for not being a believer, many people would come up to me — it still sometimes happens — and ask me if Carl changed at the end and converted to a belief in an afterlife. They also frequently ask me if I think I will see him again.

Carl faced his death with unflagging courage and never sought refuge in illusions. The tragedy was that we knew we would never see each other again. I don’t ever expect to be reunited with Carl. But, the great thing is that when we were together, for nearly twenty years, we lived with a vivid appreciation of how brief and precious life is. We never trivialized the meaning of death by pretending it was anything other than a final parting.

Every single moment that we were alive and we were together was miraculous-not miraculous in the sense of inexplicable or supernatural. We knew we were beneficiaries of chance. . . . That pure chance could be so generous and so kind. . . . That we could find each other, as Carl wrote so beautifully in Cosmos, you know, in the vastness of space and the immensity of time. . . . That we could be together for twenty years. That is something which sustains me and it’s much more meaningful. . . .

The way he treated me and the way I treated him, the way we took care of each other and our family, while he lived. That is so much more important than the idea I will see him someday. I don’t think I’ll ever see Carl again. But I saw him. We saw each other. We found each other in the cosmos, and that was wonderful.”

In writing this moving tribute for her husband, Druyan’s words perfectly captures why Sagan remains so beloved to this day.

“There is something in his delivery that communicates his genuine enthusiasm and awe for the universe and for science, and that just cuts straight to my heart,” Columbia University astrophysicist Summer Ash tells Inverse. “That letter is something I always try to keep in mind when interacting with students and kids. I want to do everything in my power to fan the flames for future thinkers behind me.”

Happy 83rd, Carl Sagan. From all of us here on the Pale Blue Dot, ad astra.