Armstrong, Aldrin, Shepherd, Glenn, Gagarin. If the names sound familiar, they should.

In October 1957, the Soviet Union launched the first artificial satellite into space. The 23-inch, 184-pound Sputnik 1 spent almost three months orbiting Earth, and its successful launch began man’s exploration into the vast unknown.

Six decades later, companies race to privatize personal space travel, and it’s likely only a matter of time before humans head to space on a regular basis. This would never be possible if it weren’t for the men and women who paved the way to the stars.

Who were they, and why are they worth remembering? Here are a few of the most famous astronauts in history:

Yuri Gagarin

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Twenty-seven-year-old Russian cosmonaut Yuri Gagarin is the most important figure in space travel simply because he was the first.

On April 12, 1961, aboard the Vostok 1, Gagarin became the first human to travel from the surface of Earth to the weightlessness of outer space. His 108-minute orbital flight took him once around the planet, and upon landing, he became an instant international celebrity.

Gagarin would never return to space. He was killed on March 27, 1968 while piloting a jet during a routine training flight.

Alan Shepard

Credit: NASA

Not to be outpaced in the Space Race by the Russians, 38-year-old American astronaut Alan Shepard brought the United States to space on May 5, 1961 aboard the Freedom 7 spacecraft. He traveled over 300 miles during his 15-minute initial flight.

Shepard was one of seven men chosen as part of the Project Mercury program. He and his six companions (Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, and Deke Slayton) were dubbed the Mercury 7 and would pilot the manned Mercury spaceflights from 1961 to 1963.

Shepard would not return to space for almost a decade due to an ear problem diagnosed as Meniere’s disease. On January 31, 1971, as part of the Apollo 14 mission, Shepard spent more than 30 hours on the moon. While there, he added to his list of out-of-this-world accomplishments by being the first to play golf on the moon’s surface.

Valentina Terishkova

Credit: NASA

Russian cosmonaut Valentina Terishkova joined Garagin and Shepherd as an outer space pioneer when she became the first woman to exit the atmosphere on June 16, 1963.

Aboard the Vostok 6, Terishkova spent almost three days in space and circled the Earth a total of 48 times, logging more flight time than all American astronauts who’d gone before her. She was only 26 at the time, 10 years younger than the youngest member of the Mercury 7, Gordon Cooper.

Terishkova would not return to space, and neither would another woman for almost twenty years.

Gus Grissom, Ed White, and Roger Chaffee

Credit: NASA

After space, man set his sights on the moon. The Apollo program was dedicated to landing a man on the moon and safely returning him to Earth.

Astronauts Virgil “Gus” Grissom, Ed White, and Roger Chaffee are recognized for their deaths aboard the Apollo 1 on January 27, 1967. A cabin fire erupted during a preflight launch rehearsal test at the Cape Kennedy Air Force Station Launch Complex, destroying the command module and killing the three astronauts aboard.

Grissom had been a member of the Mercury 7, White made a name for himself as the first American to walk in space, and Chaffee served as capsule communicator for the Gemini 3 and Gemini 4 missions.

Neil Armstrong and Buzz Aldrin

Credit: NASA

Neil Armstrong is also one of space travel’s most significant figures because he was the first man to set foot on the surface of the moon.

In mid-July, the Apollo 11 spacecraft blasted off toward the moon. On July 21, 1969 at 2:56:15 GMT/UTC, Armstrong’s iconic words, “One small step for (a) man; one giant leap for mankind” were broadcast back to the world as he stepped from the Eagle lunar landing module to the moon’s surface.

Second out of the Eagle lunar lander, and second to step foot on the moon, was astronaut Edwin “Buzz” Aldrin. Aldrin and Armstrong spent almost two hours walking on the moon—they took photos, deployed instruments, and collected samples—and almost two days on the moon’s surface in total.

Neither Armstrong nor Aldrin returned to space (although they had both been once before on the Gemini 8 and Gemini 12 missions, respectively). Armstrong was 38 and Aldrin was 39 at the time of the Apollo 11 mission.

Honorable mentions

There are a number of worth-mentioning astronauts, cosmonauts, and experts who helped and continue to help foster interest and excitement in space travel. Unfortunately, they can’t all be listed here. A few honorable mentions include:

The Mercury 13 – Thirteen American women made the cut, trained, readied themselves to travel into space, and were dubbed the Mercury 13 during the 1960s. The program was shut down amid a culture of sexism.

John Glenn – First American man to orbit the Earth on February 20, 1962.

Alexy Leonov – First man to walk in space and conduct extravehicular activity outside of a space shuttle on March 18, 1965.

Sally Ride – First American woman and youngest American astronaut in space on June 18, 1983.

Scott Kelly and Chris Hadfield – Astronauts who, individually, became popular modern personalities through the work they performed on the International Space Station and shared with the public.