Isaac Asimov described the solar system as the Sun, Jupiter, and debris. He wasn't wrong—the Sun is 99.8 percent of the mass of the solar system. But what is the giant ball of fire in the sky? How does it behave and what mysteries remain? Mental Floss spoke to Angelos Vourlidas, an astrophysicist and the supervisor of the Solar Section at Johns Hopkins University Applied Physics Laboratory, to learn what scientists know about the Sun—and a few things they don't.
1. IT'S A GIANT NUCLEAR FUSION REACTOR.
The Sun is so incomprehensibly big that it's almost pointless to bother trying to imagine its size. Our star is about 860,000 miles across. It is so big that 1.3 million Earths could fit inside of it. The Sun is 4.5 billion years old, and should last for another 6.5 billion years. When it faces the final curtain, it will not go supernova, however, as lacks the mass for such an end. Rather, the Sun will grow to a red giant—destroying the Earth in the process, if we last that long, which we won't—and then contract down to become a white dwarf.
The Sun is 74 percent hydrogen and 25 percent helium, with a few other elements thrown in for flavor, and every second, nuclear reactions at its core fuse hundreds of millions of tons of hydrogen into hundreds of millions of tons of helium, releasing the heat and light that we love so very much.
2. IT HAS A GALACTIC-SCALE ORBIT.
The Sun rotates, though not quite the same way as a terrestrial planet like the Earth. Like the gas and ice giants, the Sun's equator and poles complete their rotations at different times. It takes the Sun's equator 24 days to complete a rotation. Its poles poke along and rotate every 35 days. Meanwhile, the Sun actually has its own orbit. Moving at 450,000 miles per hour, the Sun is in orbit around the center of the Milky Way galaxy, making a full loop every 230 million years.
3. IT'S HOT IN ODD WAYS.
The solar corona as captured every two hours for four days. Red is cool (~80,000°F), while yellow is hot (~2,800,000°F).
Angelos Vourlidas, JHU/APL
The Sun's temperatures leave astrophysicists puzzled. At its core, it reaches a staggering 27,000,000°F. Its surface is a frosty 10,000°F, which, as NASA notes, is still hot enough to make diamonds boil. Here's the weird part, though. Once you get into the higher parts of the Sun's corona, temperatures again rise to 3,500,000°F. Why? Nobody knows!
4. THE SUN HAS AN ATMOSPHERE—AND THE EARTH IS INSIDE IT.
If you saw the total solar eclipse earlier this year, you saw the Sun turn black, ringed by a shimmering white corona. That halo was part of the Sun's atmosphere. And it's a lot bigger than that. In fact, the Earth is inside of the Sun's atmosphere. "It basically goes as far away as Jupiter," Vourlidas tells Mental Floss. The Sun is a semi-chaotic system. Every 100 years or so, the Sun seems to go into a small "sleep," and for two or three decades, its activity is reduced. When it wakes, it becomes much more active and violent. Scientists are not sure why that is. Presently we are in one of those solar lulls.
5. THE IRON IN YOUR BLOOD COMES FROM THE SUN'S SIBLINGS.
The Sun lacks a solid core. At 27,000,000°F, it's all plasma down there. "That's where most of the heavy elements like iron and uranium are created—at the cores of stars," Vourlidas says. "When the stars explode, they are released into space. Planets form out of that debris, and that's where we get the same iron in our blood and the carbon in our cells. They were made in some star." Not ours, obviously, but a star that exploded in our neighborhood before our Sun was born. Other elements created from the cores of stars include gold, silver, and plutonium. That is what Carl Sagan meant when he said that we are children of the stars.
6. THE HOLY GRAIL OF SUN SCIENCE IS UNDERSTANDING ERUPTIONS.
The ability to predict solar storms is the holy grail for astrophysicists who study the Sun. During a coronal mass ejection, a billion tons of plasma material can be blown from the Sun at millions of miles per hour. The eruptions carry around 300 petawatts of energy—that's 50,000 times the amount of energy that humans use in a single year. As the structures travel from the Sun, they expand, and when they hit the Earth, a percentage of their energy is imparted. Those impacts can create havoc. Spacecraft are affected, airliners receive surges of x-rays, and the energy grid can be disrupted—one day perhaps catastrophically so. "Our models say it can happen every 200 years," says Vourlidas, "but the Sun doesn't know about our models."
The last such strike on the Earth is believed to have occurred in 1859. The telegraph system collapsed, but the effect on society was minimal overall. (The widespread use of electric lighting and the first power grids were still decades away.) If the Earth were to sustain a similar such destructive event today, the effects might be devastating. "It is the most violent phenomenon in our solar system," Vourlidas explains. "We need to know when such an amount of plasma has left the Sun, whether it will hit the Earth, and how hard it is going to slap us." Such foresight would allow spacecraft to power down sensitive instruments and power grids to switch off where necessary, among other things.
7. NASA'S NEXT STOP: THE SUN.
Wind moving off of the Sun in visible light. If you were in a spaceship and didn't melt, that's what you would see. The zooming effect simulates what an imager on the Parker Solar Probe will see.
Angelos Vourlidas, JHU/APL
Next year, NASA will launch the Applied Physics Laboratory's Parker Solar Probe to "kiss" the Sun. It will travel to within 4 million miles of our star—the closest we've ever come—and will study the corona and the solar wind. "At the moment, the only way we understand that system is by seeing what the properties of the wind are at Earth, and then trying to extrapolate back toward the Sun," says Vourlidas. "It's an indirect exercise. But the probe will measure the wind—how fast it is, how dense, what is the magnetic field—across multiple locations as it orbits the Sun." Once scientists get those measurements, theorists will attempt to devise new models of the solar wind, and ultimately help better predict solar storms and space weather events.
Neil Armstrong, Michael Collins, and Buzz Aldrin share a laugh with President Richard Nixon while aboard the USS Hornet on July 24, 1969.
Richard Nixon Foundation via Getty Images
In July 1969, the world watched as the crew of Apollo 11 successfully entered lunar orbit, landed, then blasted off and returned to Earth. At each step of the way there were dangers and NASA had backup plans in case something went terribly wrong—though there wasn't much NASA could do from 384,403 kilometers away. In 1999, William Safire discussed the speech he wrote for President Richard Nixon just in case the mission failed. From Safire's article:
The most dangerous part of the trip was not landing the little module on the moon, but in launching it back up to the mother ship. If that failed, Neil Armstrong and Buzz Aldrin could not be rescued. Mission Control would have to "close down communications" and, as the world agonized, let the doomed astronauts starve to death or commit suicide.
Nixon aides H. R. Haldeman and Peter Flanigan told me to plan for that tragic contingency. On July 18, 1969, I recommended that "in event of moon disaster . . . the President should telephone each of the widows-to-be" and after NASA cut off contact "a clergyman should adopt the same procedure as a burial at sea, commending their souls to 'the deepest of the deep,' concluding with the Lord's Prayer." A draft Presidential speech was included.
Here's a scan of the speech:
And here's the text:
IN EVENT OF MOON DISASTER:
Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace.
These brave men, Neil Armstrong and Edwin Aldrin, know that there is no hope for their recovery. But they also know that there is hope for mankind in their sacrifice.
These two men are laying down their lives in mankind's most noble goal: the search for truth and understanding.
They will be mourned by their families and friends; they will be mourned by their nation; they will be mourned by the people of the world; they will be mourned by a Mother Earth that dared send two of her sons into the unknown.
In their exploration, they stirred the people of the world to feel as one; in their sacrifice, they bind more tightly the brotherhood of man.
In ancient days, men looked at stars and saw their heroes in the constellations. In modern times, we do much the same, but our heroes are epic men of flesh and blood.
Others will follow, and surely find their way home. Man's search will not be denied. But these men were the first, and they will remain the foremost in our hearts.
For every human being who looks up at the moon in the nights to come will know that there is some corner of another world that is forever mankind.
If you were born after the Apollo program, and maybe even if you remember those days, it seems almost unbelievable that NASA sent manned missions to the moon 239,000 miles away. People continue to express sadness at the fact that the Apollo lunar missions were so long ago, and that soon there will be no one left alive who actually went to the moon. we celebrate the 50th anniversary of the Apollo 11 mission, now is the perfect time to remember—or get to know—the only 12 people who ever walked on a body other than planet Earth.
1. Neil Armstrong
NASA/HULTON ARCHIVE/GETTY IMAGES
Navy test pilot, engineer, and Korean War veteran Neil Armstrong left the Navy in 1952, but continued in the Naval Reserve. He worked as an experimental test pilot for the National Advisory Committee for Aeronautics (NACA) beginning in 1955, which evolved into NASA. Armstrong was assigned as an astronaut in 1962, and flew on the Gemini 8 mission in 1966, where he performed the first successful space docking procedure. Armstrong was selected to be the first man to walk on the moon, as the Apollo 11 mission was planned, for several reasons: he was the commander of the mission, he didn't have a big ego, and the door of the lunar lander was on his side. Although the first steps on the moon are what he will always be known for, Armstrong considered the mission's biggest accomplishment was landing the lunar module. He later said,
Pilots take no special joy in walking: pilots like flying. Pilots generally take pride in a good landing, not in getting out of the vehicle.
Armstrong along with his crew were honored with parades, awards, and acclaim after their return to Earth, but Armstrong always gave credit to the entire NASA team for the Apollo moon missions. He resigned from NASA in 1971 and became a professor of of Aerospace Engineering at the University of Cincinnati for eight years. Armstrong served on the boards of many corporations and foundations, but gradually withdrew from publicity tours and autograph signings. He didn't particularly care for fame.
“For those who may ask what they can do to honor Neil, we have a simple request. Honor his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down at you, think of Neil Armstrong and give him a wink.”
2. Edwin "Buzz" Aldrin
After graduating third in his class at West Point in 1951 with a degree in science, Buzz Aldrin flew 66 combat missions as an Air Force pilot in the Korean War. Then he earned a PhD at MIT. Aldrin joined NASA as an astronaut in 1963. In 1966 he flew in the Gemini 12 spacecraft on the final Gemini mission.
Aldrin accompanied Neil Armstrong on the first moon landing in the Apollo 11 mission, becoming the second person, and now the first of the living astronauts, to set foot on the moon. Aldrin had taken a home Communion kit with him, and took Communion on the lunar surface, but did not broadcast the fact. Aldrin retired from NASA in 1971 and from the Air Force in 1972. He later suffered from clinical depression and wrote about the experience, but recovered with treatment. Aldrin has co-authored five books about his experiences and the space program, plus two novels. Aldrin, who is now 89 years old, continues to work to promote space exploration.
3. Charles "Pete" Conrad
Astronaut Charles 'Pete' Conrad stands next to the Surveyor 3 lunar lander on the Moon, during NASA's Apollo 12 lunar landing mission, November 1969.
Space Frontiers/Getty Images
Pete Conrad was a Princeton graduate and Navy test pilot before entering the astronaut corps in 1962. He flew on the Gemini V mission and was commander of Gemini XI. Conrad was commander of the Apollo 12 mission, launched during a lightning storm which temporarily knocked out the command module's power shortly after liftoff. When Conrad stepped onto the moon, he said,
Whoopee! Man, that may have been a small one for Neil, but that's a long one for me.
Conrad later flew on the Skylab 2 mission as commander with the first crew to board the space station. He retired from NASA and the Navy in 1973, after which he worked for American Television and Communications Company and then for McDonnell Douglas.
Pete Conrad died on July 8, 1999 in a motorcycle accident. He was 69.
4. Alan L. Bean
Space Frontiers/Getty Images
Apollo astronaut Alan Bean was the fourth man to walk on the moon, during the Apollo 12 mission in 1969. He was the lunar module pilot. Bean was also the commander of the Skylab Mission II in 1973, which spent 59 days in flight. Altogether, Bean logged 1,671 hours and 45 minutes in space. Bean is the only artist to have visited another world, so his paintings of the lunar environment have the authenticity of an eyewitness. He retired from the Navy with the rank of Captain, but continued to train astronauts at NASA until 1981, when he retired to devote time to his art.
Bean died on May 26, 2018 at the age of 86.
5. Alan Shepard
Hulton Archive/Getty Images
Alan Shepard was a bona-fide space pioneer who cemented his spot in history long before the Apollo program. A U.S. Navy test pilot, he was selected as one of the original Mercury astronauts in 1959. Shepard was the first American launched into space aboard the Freedom 7 spacecraft on May 5, 1961. His suborbital flight reached an altitude of 116 miles.
Barred from flight during the Gemini program because of an inner ear problem, Shepard had the problem fixed surgically and was assigned as commander of the Apollo 14 mission to the moon. He was responsible for the most accurate lunar module landing ever, and spent 9 hours and 17 minutes exploring the moon's surface outside the module. During that time, he famously knocked a couple of golf balls with a six-iron attached to his sample-collecting tool. With one arm (due to the space suit), he managed to drive further than professional golfers on Earth could ever hope to, thanks to the moon's lower gravity.
Before and after his Apollo mission, Shepard served as Chief of the Astronaut Office. He retired from NASA and the Navy in 1974, having achieved the rank of Rear Admiral. Shepard went into private business, serving on the board of several corporations and foundations. He founded Seven Fourteen Enterprises, an umbrella corporation named after his two space missions. Shepard wrote a book with Deke Slayton, Moon Shot: The Inside Story of America's Race to the Moon. Shepard compared his book to The Right Stuff by Tom Wolfe, saying, "'We wanted to call ours 'The Real Stuff,' since his was just fiction.''
Alan Shepard died on July 21, 1998 at the age of 74.
6. Edgar D. Mitchell
Ed Mitchell joined the Navy in 1952 and became a test pilot. Then he earned a PhD in Aeronautics and Astronautics from MIT. NASA selected him for the astronaut corps in 1966. In January of 1971, Mitchell flew on Apollo 14 as lunar module pilot, becoming the sixth man to walk on the lunar surface. He retired in 1972 and founded the Institute of Noetic Sciences, which explores psychic and paranormal events. Mitchell gained some notoriety after NASA for his views on UFOs, as he has asserted that the government is covering up evidence at Roswell. His information, he admitted, came secondhand from various sources.
Mitchell died on February 4, 2016, the eve of the 45th anniversary of his lunar landing.
7. David Scott
NASA/Liaison via Getty Images Plus
David Scott joined the Air Force after graduating from West Point. Selected as an astronaut in 1963, he flew with Neil Armstrong on the Gemini 8 mission and was command module pilot on Apollo 9. Scott then went to the moon on Apollo 15, which landed on the lunar surface on July 30, 1971. It was the first mission to land near mountains. Scott and Jim Irwin spent 18 hours exploring the lunar landscape in the Lunar Roving Vehicle in the first mission to use such a vehicle to travel on the moon.
Scott became famous for the "postage stamp incident," in which he took unauthorized postage stamp covers to the moon with the intent to sell them afterwards. NASA had turned a blind eye to such activities before, but publicity over the matter caused them to discipline Scott and he never flew again. Scott retired from NASA in 1977 and served as a consultant for several movies and TV shows about the space program. He also wrote a book with former cosmonaut Alexei Leonov, Two Sides of the Moon: Our Story of the Cold War Space Race.
Air Force test pilot James Irwin became an astronaut in 1966. He was the lunar module pilot for Apollo 15 in 1971. His 18.5 hours of lunar surface exploration included gathering many samples of rocks. The astronauts' medical conditions were being monitored from Earth, and they noticed Irwin developing symptoms of heart trouble. As he was breathing 100% oxygen and under lower gravity than on Earth, mission control decided he was in the best environment possible for such irregularity -under the circumstances. Irwin's heart rhythm was normal by the time Apollo 15 returned to Earth, but he had a heart attack a few months later. Irwin retired from NASA and the Air Force (with the rank of Colonel) in 1972 and founded the High Flight Foundation in order to spread the Christian gospel during the last twenty years of his life. He notably took several groups on expeditions to Mt. Ararat to search for Noah's Ark.
James Irwin died on August 8, 1991, of a heart attack. He was 61 years old.
9. John Watts Young
Keystone/Hulton Archive/Getty Images
John Young is so far the longest serving astronaut in NASA history. He was selected as an astronaut in 1962 and his first space flight was in 1965 aboard Gemini 3 with Gus Grissom. He achieved some notoriety at that time by smuggling a corned beef sandwich onto the flight, angering NASA. But Young went on to complete a total of six space missions in the Gemini, Apollo, and the space shuttle programs. He orbited the moon on the Apollo 10 mission, then was commander of the Apollo 16 mission and became the ninth person to walk on the moon. Young was also commander of the first space shuttle flight in 1981 and returned for shuttle flight 9 in 1983, which deployed the first Spacelab module. Young was also scheduled for another space shuttle flight in 1986, which was delayed after the Challenger disaster, so the veteran astronaut never made his seventh flight. Young finally retired from NASA after 42 years of service in 2004.
John Young died on January 5, 2018 at the age of 87 following complications with pneumonia.
Astronaut Charles Duke was capcom during the Apollo 11 mission. His is the voice you recall saying, "Roger, Twank... Tranquility, we copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot!" when the lunar module landed on the moon. Duke also made history by catching German measles while training in the backup crew for the Apollo 13 mission, exposing the crew to the disease and causing Ken Mattingly to be replaced by Jack Swigart on that terrifying spaceflight. Duke went to the moon (with Mattingly as command module pilot) on the Apollo 16 mission in April of 1972. He retired from NASA in 1975 having reached the rank of Brigadier General in the U.S. Air Force, and founded Duke Investments. Duke also became a Christian and a lay minister to prison inmates.
Charles Duke is 83 years old.
11. Harrison "Jack" Schmitt
Space Frontiers/Getty Images
Jack Schmitt was a geologist first, and trained as a pilot only after becoming a NASA astronaut. In fact, he was only the second civilian to fly into space, after Neil Armstrong, who was a veteran at the time of his flights. Schmitt was assigned to fly to the moon on the Apollo 18 mission, but when the Apollo 18 and 19 missions were cancelled in September of 1970, the scientific community lobbied to have Schmitt reassigned to Apollo 17 (replacing Joe Engle) as lunar module pilot. He was the first scientist in outer space. On the Apollo 17 mission, he and Gene Cernan spent three days on the lunar surface (a record) and drove their Lunar Roving Vehicle around collecting samples, conducting experiments, and leaving measuring instruments behind. Schmitt and Cernan gathered 250 pounds of lunar material to take back.
After resigning from NASA in 1975, Schmitt, a Republican, was elected Senator for New Mexico and served from 1977 to 1983. He became an adjunct professor at the University of Wisconsin–Madison, and lives in Silver City, New Mexico. In recent years, Dr. Schmitt's scientific background and political leanings have kept him in the spotlight as he has said that the concept of climate change is "a red herring," and that environmentalism is linked with communism.
Jack Schmitt is 84 years old.
12. Eugene E. Cernan
As a Navy pilot, Gene Cernan logged over 5,000 hours flying time. He was accepted into the astronaut program in 1963. Cernan's first space flight was on Gemini IX in 1966, in which he conducted extravehicular activities (a space walk), followed by the Apollo 10 mission in May of 1969, which orbited the moon. Cernan was assigned commander of the Apollo 17 mission before anyone knew it would be the last Apollo mission. Even after the Apollo program was cut, no one knew for sure that travel to the moon would be abandoned for decades. When Schmitt and Cernan boarded their lunar module for the last time on December 13th, 1972, Cernan said:
"I'm on the surface; and, as I take man's last step from the surface, back home for some time to come — but we believe not too long into the future — I'd like to just [say] what I believe history will record. That America's challenge of today has forged man's destiny of tomorrow. And, as we leave the Moon at Taurus-Littrow, we leave as we came and, God willing, as we shall return: with peace and hope for all mankind. Godspeed the crew of Apollo 17."
Cernan retired from the Navy and from NASA in 1976. He went on to found an aerospace technology firm, and wrote a book about his experiences as an astronaut. He also contributed his talents to ABC-TV as a commentator during shuttle flights and has made appearances on various space specials. In September of 2011, Cernan testified before Congress on the future of the space program.
The space program has never been an entitlement, it's an investment in the future - an investment in technology, jobs, international respect and geo-political leadership, and perhaps most importantly in the inspiration and education of our youth. Those best and brightest minds at NASA and throughout the multitudes of private contractors, large and small, did not join the team to design windmills or redesign gas pedals, but to live their dreams of once again taking us where no man has gone before.