152 years ago, a man in England named Richard Carrington discovered solar
flares. It happened at 11:18 AM on the cloudless morning of Thursday, September
Just as usual on every sunny day, the 33-year-old solar astronomer was busy in
his private observatory, projecting an image of the sun onto a screen and
sketching what he saw. On that particular morning, he traced the outlines of an
enormous group of sunspots. Suddenly, before his eyes, two brilliant beads of
white light appeared over the sunspots; they were so bright he could barely
stand to look at the screen.
Carrington cried out, but by the time a witness arrived minutes later, the first
solar flare anyone had ever seen was over.
It would not be the last. Since then, astronomers have recorded thousands of
strong flares using instruments ranging from the simplest telescopes in backyard
observatories to the most complex spectrometers on advanced spacecraft.
Possibly no other phenomenon in astronomy has been studied as much. After all
that scrutiny, you might suppose that everything about solar flares would be
known. Far from it.
Last week, researchers announced that solar flares have been keeping a secret —
and it's a big one.
"We've just learned that some flares are many times stronger than previously
thought," says University of Colorado physicist Tom Woods who led the research
"Solar flares were already the biggest explosions in the solar system and this
discovery makes them even bigger."
NASA's Solar Dynamics Observatory, launched in February 2010, revealed the
secret: About 1 in 7 flares experience a sort of "aftershock."
Ninety minutes or so after the flare dies down, it springs to life again,
producing an extra surge of extreme ultraviolet radiation. "We call it the 'late
phase flare,'" says Woods.
"The energy in the late phase can exceed the energy of the primary flare by as
much as a factor of four."
The extra energy has a big effect on Earth. Extreme ultraviolet wavelengths are
particularly good at heating and ionizing Earth's upper atmosphere. When our
planet's atmosphere is heated by extreme UV radiation, it puffs up, accelerating
the decay of low-orbiting satellites. Furthermore, the ionizing action of
extreme UV can bend radio signals and disrupt the normal operation of GPS.
SDO was able to make the discovery because of its unique ability to monitor the
sun's extreme UV output in high resolution 24 hours a day, 7 days a week.
With that kind of scrutiny, it's tough to keep a secret, even one that's 152
To learn more secrets of astronomy, visit science.nasa.gov.