John Glenn, who was the first American to orbit Earth, has passed away at the age of 95 in Columbus, Ohio.
Glenn was also a decorated war hero, former astronaut and senator, educator, husband, father of two, and defender of humanity who worked against the proliferation of nuclear weapons.
In the wake of the news, scientists and space luminaries have taken to Twitter with an outpouring of condolences, memories, and love.
We'll update the list here as more space-related celebrities chime in, but below are some of the more notable tweets we've seen:
Paul Allen, Microsoft co-founder, philanthropist, and creator of private aerospace company Stratolaunch Systems
RIP John Glenn, first American to orbit our planet and space pioneer. https://t.co/lyTgT3Djlc— Paul Allen (@PaulGAllen) December 8, 2016
Peggy Whitson, a US astronaut and the first female commander of the International Space Station
Mae Jemison, the first woman of colour in space and leader of the 100 Year Starship project
Saddened by passing of John Glenn, 1st American to orbit Earth, original Mercury astronaut, US Senator and oldest person to go into space. pic.twitter.com/kpXKv2MLYy— Dr. Mae Jemison (@maejemison) December 8, 2016
I offer a celebratory salute to Glenn's life, the epitome of courage exploration & commitment to public service. An honor to be in his field pic.twitter.com/Z72MZXm6Fi— Dr. Mae Jemison (@maejemison) December 8, 2016
Neil deGrasse Tyson, an astrophysicist and populariser of science
Aren't many Heroes left: WWII & Korean War Fighter Pilot. Marine Colonel. NASA Astronaut. Senator. Married 73 yrs. John Glenn RIP 1921-2016— Neil deGrasse Tyson (@neiltyson) December 8, 2016
Jeff Bezos, the founder of Amazon and spaceflight company Blue Origin
Thank you, John Glenn. Godspeed.— Jeff Bezos (@JeffBezos) December 8, 2016
Scott Kelly, a US astronaut who spent more than 520 days in space
Chris Hadfield, a Canadian astronaut and former International Space Station commander
A great American, a life of service, an inspiration to us all. Goodbye, John Glenn. Godspeed. pic.twitter.com/duCA8qPYER— Chris Hadfield (@Cmdr_Hadfield) December 8, 2016
Carolyn Porco, a lead scientist on NASA's Cassini mission at Saturn
Oh so sad. John Glenn has left us. He was of a time when character & moral standing meant something, when humans touched the sky. Goodbye. pic.twitter.com/tp1n7wSaA5— Carolyn Porco (@carolynporco) December 8, 2016
Elon Musk, PayPal co-founder and founder of SpaceX
A life well lived https://t.co/NZcRZUDroH— Elon Musk (@elonmusk) December 8, 2016
Bill Nye, "the science guy" and CEO of the Planetary Society
Space exploration brings out our best. John Glenn served his country in space, in Congress, and inspired a generation. Onward, John Glenn. pic.twitter.com/KLtzuXn9eP— Bill Nye (@BillNye) December 8, 2016
This article was originally published by Business Insider.