This past fall, solar flareslarge jolts of energy from the sun—were forecast to interrupt communication and GPS devices. Nothing happened. In 2006, U.S. government researchers predicted that the next cycle of sunspots, the magnetic regions on the sun that appear as dark spots, would be as much as 50 percent stronger than the previous one, citing a “newly developed [computer] model” boasting “more than 98 percent accuracy.” Instead, that sunspot cycle, in progress now, is on track to be the weakest in nearly a century. Recently, a scientist told CNN that storms on the sun could “bring down satellites … interrupt our power grid,” and cause “trillions of dollars” in damage. Perhaps, but the ponies may be a better wager. And here’s a really scary prediction to worry about: London’s Telegraph newspaper warned in 2010 that solar activity could erase your iPod!
With the world increasingly dependent on electronics, “space weather”—variances in flares and solar wind (charged particles) emitted by the sun—is attracting more attention. Yet despite the possible vulnerability of the modern economy to solar activity, not to mention the simple magnitude of Sol and life’s reliance on it, our knowledge of the star is surprisingly rudimentary. “We are a long way from being able to predict how the sun will behave,” says Daniel Baker, a solar-study specialist who directs the Laboratory for Atmospheric and Space Physics at the University of Colorado.
Researchers think they have a good idea of what happens inside the sun. Hydrogen, the lightest element and the sun’s primary constituent, fuses to become helium, releasing energy. Eventually, long after humanity has gone extinct or evolved into some other form, Sol’s hydrogen will be consumed. Then the helium will begin to fuse into medium-weight elements. An eon after that, the medium-weight elements will begin to fuse into metals. Ultimately Sol will explode, scattering heavy elements into the cosmos. It’s thought that all the heavy elements of the universe were forged within stars that later exploded, supernovas having been more common when the firmament was young. The Earth, your body—both are composed of elements made inside ancient stars that exploded.
Scientists are confident that the sun is in its “main sequence”: it has burned at about the same heat for perhaps a billion years, and it’s likely to stay at about the same rheostat setting for another billion years or so. The numbers involved are staggering. The sun consumes about 600 million tons of hydrogen per second. At that rate, the mass of the Earth would be gone in 70,000 years. Yet Sol so far has exhausted only a small percentage of its energy potential. Though 93 million miles away, the sun shines so fiercely that it dazzles the eyes and makes the skin sting in summertime. And that’s after almost all of its output simply radiates off into the void: for every one unit of solar energy that impacts the Earth, 1.6 billion units do not. Life on Earth depends on the sun’s table scraps.
Though science may have a clear idea of the life cycle of stars, details are elusive. Exactly why sunspots form and disappear continues to engage speculation. They have some relation to the titanic magnetism that fluctuates through the sun, but the exact relationship is uncertain, hence the poor track record of prediction. The solar winds vary, and occasionally a “coronal mass ejection” sends a hunk of Sol hurtling outward into the solar atmosphere. But here, too, details are uncertain.
In the short time that researchers have been monitoring the sun closely, its luminosity has shown almost no variance, which would suggest that the roughly one degree Fahrenheit of global warming observed in the past century has been caused by something other than Sol ramping up. On the other hand, NASA’s recently launched Kepler spacecraft has begun inspecting “nearby” sun-like stars, and is finding that their output changes more than expected, says Daniel Baker. So solar variation might play some role in climate trends. Solar wind and other forces from the sun also affect the temperature and density of the Earth’s upper atmosphere, and that may influence the climate. But if you hear a talk-radio host say the sun is accelerating global warming, remember: even if that turns out to be true, nothing can be done about the output of our star.
Knowledge of the sun is expected to improve: NASA’s Solar Dynamics Observatory, launched in 2010, is already producing dramatic photography of the sun, and returning data on solar magnetism. Several solar probes and telescopes will launch in the coming decade, including a NASA probe that will draw closer to the sun than any previous mission. “Ideally, we should have a network of solar satellites similar to the network of weather satellites,” Baker says, “with many satellites around the sun, and also in positions both ahead of and behind Earth’s orbit within the solar system.” Considering that the Solar Dynamics Observatory cost nearly $1 billion, a full array of sun monitors in space could easily run $10 billion, if not more. But then, NASA spent anywhere from $40 billion to $100 billion on the International Space Station, with no tangible benefit to taxpayers. Improved understanding of the sun, by contrast, would clearly be in the public interest.
At least the sun seems unlikely to explode anytime soon. Standard conjecture regarding the inner processes of stars holds that they emit cornucopian amounts of neutrinos, which are subatomic particles. A generation ago, when the first neutrino-detectors were built, they didn’t find anything close to the expected number of neutrinos from the sun. This led the late science-fiction writer Arthur C. Clarke, who is credited with the concept of the telecommunications satellite, to speculate that Sol was about to explode, and the human experiment to reach an untimely end.
Today, researchers believe that prior assumptions about solar neutrinos were in error. The sun seems fine. It’s not about to explode. Probably. We think.
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