7 Shining Facts About the Sun

NASA
NASA

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.

Editor's Note: This post has been updated. 

Ad Astra: The Time Earth Almost Got a Space Billboard

iStock
iStock

In the 1980s and well into the 1990s, everything associated with Arnold Schwarzenegger was big. Big biceps (22 inches during his bodybuilding heyday). Big box office (1991's Terminator 2: Judgment Day made $520 million worldwide, the highest-grossing movie of that year). So it was no surprise to open a newspaper in 1993 and see that Columbia Pictures was spending $500,000 to plaster the actor's name and the title of his pending summer blockbuster, Last Action Hero, on the fuselage of a NASA rocket set for launch that June. Schwarzenegger himself was scheduled to push the button that would propel the spacecraft into orbit.

The NASA project deal was being brokered for commercial advertising purposes by Space Marketing Inc., an Atlanta-based firm specializing in sponsorships and ads located outside of the atmosphere. The company's CEO, Mike Lawson, told the Los Angeles Times that he could've sold "dozens" of ads for the rocket, but that he and NASA officials didn't want it to "look like a pace car at the Indy 500."

The idea of promoting a movie in space was brazen, but not nearly as much as another, more ambitious project that Lawson was planning. If everything went according to plan, his Space Marketing would shoot a payload into space in time for the 1996 Summer Olympic Games in Atlanta. Once it was in orbit, mylar tubes would inflate with gas and spring open to support a mile-wide, quarter-mile tall reflective sheet that would be visible from Earth. Lawson called it an "inflatable platform," but the press—and critics—quickly labeled it something else: a space billboard.

If Lawson had his way, it would be able to make everything from the Olympic rings to the McDonald's logo as visible to Earthbound consumers as a full moon.

 

In Robert Heinlein's 1950 novella The Man Who Sold the Moon, a lunar entrepreneur hustles to sell advertising space on the moon as part of his attempt to make colonization a profitable venture. Lawson—a onetime director of marketing for his father's publishing company in Atlanta and a fan of science fiction—read the story. In 1988, he founded Space Marketing as a way to defictionalize the concept.

As fantastic as it sounded, the idea wasn't without precedent. In 1981, telecommunications mogul Robert Lorsch made a presentation to Congress that outlined a strategy for allowing corporations to "sponsor" space travel by letting them buy plaques that would go onboard spacecraft. In the same way they endorsed the Olympics, Lorsch said, corporate America could help subsidize space travel.

A McDonald's logo is visible from space
iStock Collage

The plan was a response to then-president Ronald Reagan's plea to have the private sector assist in helping the government overcome their financial burdens. While Lorsch's proposal was prescient—it anticipated the rise of privatized space exploration—the idea of having commercial sponsors for NASA didn't make it through the Byzantine maze of Washington bureaucracy.

Lawson thought the idea could be taken further, and not necessarily with the cooperation of government. Partnering with scientists at the Lawrence Livermore National Library and the University of Colorado, Lawson developed a plan to allow instruments developed by these institutions to go into orbit and collect information about the ozone layer. To underwrite the project, he would solicit commercial advertisers for the mile-long mylar sheet that would exit the atmosphere rolled up and then expand to full size once it reached orbit. The aluminized lettering would reflect the sun's rays, making whatever graphic it displayed visible for 10 minutes at a time at any given point on Earth. After roughly 20 days, it would disintegrate, leaving the sensors behind to continue collecting data for researchers.

'We could actually fly [the] Golden Arches in space," Lawson said in May 1993, referring to the ubiquitous McDonald's logo. With an estimated launch cost of $15 to $30 million, companies buying ads would cover expenses as well as contribute to a profit for Space Marketing—perhaps paying as much as $1 million for every day it was visible.

A few months later, the city of Atlanta began investigating Space Marketing's concept as a possible advertising vessel for the 1996 Olympics. "Special" glasses given away at point-of-purchase displays with cooperating sponsors would allow people to see the Olympic rings in orbit.

That last point appeared to be a concession to a growing chorus of concern over the idea of using space as a commercial entity. While proponents of the idea argued it was similar to blimps sailing overhead and displaying corporate propaganda messages, a coalition of scientists argued otherwise. Carl Sagan called it an "abomination," insisting that astronomy could soon become a practice of exploring the stars wedged between mile-wide ads for fast food and automobiles.

Consumer advocate Ralph Nader led a group calling for an orbital billboard ban, labeling it a practice of "defacing the heavens." Other groups decried it as commercial pollution of space and vowed to boycott any companies involved. Supporters of Nader's Public Interest Research Group picketed Space Marketing's Atlanta headquarters.

Lawson tried to parry the attacks in media, saying that the phrase "space billboard" was the source of the controversy. He preferred the term "environmental billboard" and said that the whole objective was to have a global company foot the bill for scientific research.

 

Conceptually, the idea of a floating Arby's logo the perceived size of the moon was too dystopian for lawmakers to handle. In 1993, Congress submitted legislation that would prohibit the Transportation Department from issuing a launch license to any company prepared to shoot a corporate image into space. (The bill was eventually signed into law by Bill Clinton in 2000.)

None of this publicity was particularly helpful to Space Marketing, which saw its Olympic plans wilt in the face of both legislative opposition and the probability of massive pushback from space advocacy groups. They turned their attention to Russia, which had no ethical objections to space endorsements, and facilitated a 1999 project that saw Pizza Hut attach its logo to the Proton rocket that carried supplies to the International Space Station. (The chain previously considered projecting its logo with lasers on the surface of the moon but abandoned the idea when they realized it would cost hundreds of millions of dollars.)

A rocket is propelled into space
iStock

Space Marketing's investors moved on to the blimp industry and the firm was dissolved by 2007, when Lawson became CEO of airship manufacturer Techsphere Systems. As for the Last Action Hero stunt: It dissolved when Columbia learned Lorsch was threatening legal action, claiming he owned a copyright on the idea of commercial space advertising. The movie itself also failed to launch, becoming a notorious summer bomb when it was pitted against Jurassic Park.

While space has largely been off-limits to such "obtrusive" advertising by law, not everyone agrees that's for the best. Earlier this month, it was reported that NASA is looking into selling off the naming right to its shuttles as a way to recoup some of the organization's costs. When Lorsch testified before a Senate subcommittee in 2004 to review his 1981 proposal, he said that his sponsorship program might have earned NASA $5 billion in revenue if it had been implemented.

10 Riveting Facts About Mars

Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).
Mars's dust storms can be global. In these images taken a month apart in 2001, the dust storm near the southern polar ice cap (left) soon enveloped the entire planet (right).
NASA/JPL-CALTECH/MSSS

Few celestial objects have fascinated humankind throughout history more than the Red Planet. For over a century, we've longed to know more about Mars and the beings that we speculated lived there. When NASA dispelled the notion of creatures scurrying along the rusty plains, it raised a more tantalizing prospect: that we might one day be the creatures that call Mars home.

Mental Floss spoke to Kirby Runyon, a researcher at the Johns Hopkins University Applied Physics Laboratory, and Tanya Harrison, the director of research for Arizona State University's NewSpace Initiative, to learn more about the place your kids might live one day.

1. A MARTIAN YEAR LASTS JUST UNDER TWO EARTH YEARS.

It takes 687 Earth days for the Red Planet make its way around the Sun. A Mars day—called a sol—lasts 24.6 hours, which would be a nuisance for the circadian rhythms of astronauts (but not as bad as a day on Venus, which lasts 5832 hours).

2. IT'S NOT AS HOT AS IT MIGHT LOOK.

Mars looks desert-hot—New Mexico with hazy skies, red because of its iron oxide soil—but is actually very cold, with a blistering hot sol being 70°F, and a cold sol a brisk -225°F. Its dust storms can be huge; in 2018, one storm grew so large that it encompassed the entire planet for more than a month. (You can see a similarly huge dust storm in the image above.)

3. MARS IS MUCH SMALLER THAN EARTH ...

Compared to Earth, Mars is a tiny Styrofoam ball, with a diameter just over half of ours and one-tenth of our mass. Its gravity will be an absolute nightmare for future colonists, at .38 that of their native planet. (That means a person weighing 100 pounds here would weigh just 38 pounds on Mars.)

4. ... AND ITS ATMOSPHERE IS MOSTLY CARBON DIOXIDE.

You won't want to get a breath of fresh air on Mars unless you're trying to suffocate: Its atmosphere is 95.32 percent carbon dioxide, with a little nitrogen and argon thrown in. (Earth's atmosphere, by contrast, is mostly nitrogen and oxygen.) When you do try to take that single, hopeless breath, the tears on your eyeballs, saliva in your mouth, and water in your lungs will immediately evaporate. You won't die right away, but you'll probably want to.

5. IT HAS TWO MOONS, BOTH WITH BETTER NAMES THAN OURS.

They're called Phobos and Deimos, which translate to Fear and Dread, respectively. They're shaped like potatoes and don't exactly fill the evening sky: Standing on the Martian surface, Phobos would appear to be about one-third the size of Earth's moon; Deimos would look like a bright star.

Future human Martians will have to enjoy Phobos while they can. The tidal forces of Mars are tearing Phobos apart; in 50 million years, the big potato will disintegrate.

In the meantime, Phobos is one of the stepping stones NASA plans to take on its journey to Mars. No part of human exploration of the Red Planet is easy, and before we land on Mars (and then have to figure out how to launch back into space and somehow get back to Earth), it's vastly easier to land on Phobos, do a little reconnaissance, and then take off and return home. As a bonus, on the journey to Phobos [PDF], astronauts can bring along hardware necessary for eventual Martian settlement, making the ride a lot easier for the next astronauts.

6. MARS IS HOME TO THE TALLEST MOUNTAIN IN THE SOLAR SYSTEM.

The tallest mountain on Earth, Mount Everest, is 29,029 feet tall. Olympus Mons on Mars is over 72,000 feet in height, making it the tallest mountain by far on any planet in the solar system.

Olympus Mons isn't the only extraordinary Mars feature: Mountaineers might also want to check out NASA's trail map for hiking the famous Face on Mars. If canyons are more your speed, you'll want to visit Valles Marineris. It is the size of North America and, at its bottom, four miles deep. (In the solar system, only Earth's Atlantic Ocean is deeper.) Once Earth's ice caps finish melting, you can always visit the ones on Mars. (If you have a telescope, you can easily see them; they are the planet's most distinctive features visible from your backyard.)

7. THE IDEA OF MARTIANS GOES BACK OVER A CENTURY.

That's partially because of popular fiction (War of the Worlds, the 1897 novel by H.G. Wells, sees a Martian invasion force invade England) and partially because of Percival Lowell, the famed astronomer who wrote prolifically on the canals he thought he was observing through his telescope, and why they might be necessary for the survival of the Martian people. (Mars was drying up.)

Though it's easy to dismiss such conclusions today, at the time Lowell not only popularized space science like few others, but left behind the Lowell Observatory in Flagstaff, Arizona—one of the oldest observatories in America and the place where Clyde Tombaugh discovered Pluto.

8. IF THERE ARE MARTIANS, THEY ARE MICROBES.

Today, scientists work tirelessly to unlock the complex geologic history of Mars, to determine whether life exists there today, or did long ago. "We think that Mars was most globally conducive to life around 3.5 to 3.8 billion years ago," Runyon tells Mental Floss. "In the Mars geologic history, that's the end of the Noachian and toward the beginning of the Hesperian epochs." There may once have been a hemispheric ocean on Mars. Later, the world might have alternated between being wet and dry, with an ocean giving way to massive crater lakes. Where there's water, there's a good chance of life.

"If we found life on Mars—either extinct or current—that's really interesting," says Runyon, "but more interesting than that, is whether this life arose independently on Mars, separate from Earth." It is conceivable that meteorite impacts on Earth blasted life-bearing rocks into space and eventually to the Martian surface: "A second life emergence on Mars is not just a geological question. It's a biogeochemical question. We know that Mars is habitable, but we haven't answered the question of whether it had, or has, life."

9. NASA SPENDS A LOT OF TIME OUT THERE.

Mars hasn't hurt for missions in recent years, though scientists now warn of an exploration desert beyond 2020. But that doesn't mean we humans don't have eyes on the planet. Presently in orbit around the planet are the Mars Reconnaissance Orbiter, which images and scans the planet; MAVEN, which studies its atmosphere; Mars Express, the European Space Agency's first Mars mission; MOM, the first Mars mission by the Indian Space Research Organization; the ESA's ExoMars Trace Gas Orbiter, which is searching for methane in the Martian atmosphere; and Odyssey, which studies Mars for water and ice signatures, and acts as a communications relay for vehicles on the ground.

Rolling around on the Martian surface are Curiosity and Opportunity—NASA missions both—which study Martian geology. Though the Russians and Europeans have tried mightily to do so, NASA is the only space agency to successfully land spacecraft on the Martian surface (seven times).

In November 2018, the InSight mission will land on Mars, where it will study the planet's interior. In 2020, NASA will land the Mars 2020 rover; where Curiosity studies Mars for signs of habitability, Mars 2020 will look for inhabitants.

"It is going to collect samples that will hopefully be brought back to Earth," says Runyon. "The three landing sites selected for Mars 2020 are Northeast Syrtis, Jezero Crater, and Columbia Hills within Gusev Crater, which is where the dead rover Spirit is currently sitting. Each of these sites is a hydrothermal environment dating from the Noachian-Hesperian boundary. These are some of the most perfect places to look for past signs of Martian life, and can help answer the question of whether life had a second genesis on Mars."

10. MARS IS CHANGING, BUT NOBODY KNOWS WHY.

"Most people don't realize how active Mars is," Harrison tells Mental Floss. "Other planets aren't just these dead worlds that are frozen in time outside of our own. There are actually things happening there right now." Imagery from the HiRISE and Context Camera instruments on the Mars Reconnaissance Orbiter have revealed such events as avalanches, sand dune erosion [PDF], and recurring slope lineae (flowing Martian saltwater).

Things are moving, but it's not always clear why. "There's a lot of material that has been eroded away," says Harrison. "We have entire provinces of the planet that look like they've been completely buried and then exhumed. And that's a lot of material. The big question is, where did it all go? And what process eroded it all away?" Curiosity might help answer the question, but to really understand the processes and history of the fourth rock from the Sun, we're going to need to send geologists in spacesuits. "You can't replace human intuition with a rover," Harrison says. "Looking at a picture on your computer is not the same as standing there and looking around at the context, stratigraphic columns, being able to pick up the rocks and manipulate them, take a hammer to things. So once humans land on the surface, it'll be kind of like the difference between what we knew about Mars from Viking and Mars Global Surveyor and then the revolution between Mars Global Surveyor and Mars Reconnaissance Orbiter. Our view of what we think happened on Mars is going to completely change, and we'll find out that a lot of what we thought we knew was wrong."

A version of this story ran in 2017.

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