A Thousand Years Ago, the Sun Erupted. If That Happened Now, We’d Be in Big Trouble.
In
the years 774 and 993 AD, the Earth was attacked from space. Not by
aliens, but by a natural event - and it was very, very powerful.
Whatever it was, it subtly altered the chemistry of our planet’s
atmosphere, creating trace amounts of radioactive elements like
chlorine-36, beryllium-10, and carbon-14. And those provide the clue to
what the event was: Those isotopes are created when high-energy protons
slam into our air. That means the source must have been from space.
These must have been huge waves of subatomic particles that slammed into
us on those dates. Spikes in the abundances of those elements were
found all over the world, including ice cores from the Arctic and
Antarctic, Chinese
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Nov. 9 2015 9:30 AM
When the Sun Went Medieval on Our Planet
Photo by NASA/GSFC/SDO
In the years 774 and 993 AD, the Earth was attacked from space.
Not by aliens, but by a natural event — and it was very, very powerful.
Whatever it was, it subtly altered the chemistry of our planet’s
atmosphere, creating trace amounts of radioactive elements like
chlorine-36, beryllium-10, and carbon-14. And those provide the clue to
what the event was: Those isotopes are created when high-energy protons
slam into our air. That means the source must have been from space.
These must have been huge waves of subatomic particles that
slammed into us on those dates. Spikes in the abundances of those
elements were found all over the world, including ice cores from the
Arctic and Antarctic, Chinese corals, and more. Generating that many
particles isn’t easy, and only extremely violent events can do it.
Several possible sources have been considered. One candidate is that
the Earth got caught in the beam from a gamma-ray burst, the
mind-crushingly powerful demise of a very high mass star. I wrote about this being the possible cause of the 774 event in an earlier article. However, GRB impacts don’t usually create 10Be
due to the detailed physics of the blast, so that makes a GRB as the
source shaky. Plus, they’re very rare events, so having two happen in as
many centuries is extremely unlikely (I didn’t know about the
993 AD event when I wrote that article, or else I would’ve been a lot
more likely to wonder about other sources).
New research studying the amounts of these radioactive materials in ice cores points to a different culprit, one I wouldn’t have thought possible: the Sun.
The Sun generates ridiculously strong magnetic fields in its interior, and these can store vast amounts of energy. They can release this energy explosively on the surface,
creating intense solar flares. Sometimes the loops of magnetism do this
far above the Sun’s surface, creating what are called coronal mass
ejections. These are less intense (that is, less concentrated bursts of
energy) than flares, but far larger and more powerful; think of flares
versus CMEs like solar tornadoes versus hurricanes.
You can find out more about these events in the Crash Course Astronomy episode I did on the Sun:
I also have a chapter in my book Death from the Skies! about solar storms and their effects on Earth.
When I wrote about the 774 AD event on this blog before, I mentioned
that a flare or coronal mass ejection was unlikely to be the source due
to the amount of energy needed to create these radioactive elements.
However, that new research indicates that the Sun is the most
likely culprit for this interplanetary assault, and that, in turn, means
the Sun can produce more powerful events than we previously thought.
Yikes.
Photo by ESA and NASA/SOHO
We’ve known for a long time that the Sun is capable of producing huge magnetic explosions. In 2003 it let rip a series of solar storms so powerful that one of them set the record for the biggest flare seen in modern times. And the strongest known was also very first solar explosion ever seen — called the Carrington Event,
after an astronomer who studied it — happened in 1859. It created
aurora as far south as Mexico and Hawaii! Events like that can also
create what are called geomagnetically induced currents (GICs): The
Earth’s magnetic field shakes so violently that it induces currents in
conductors on the ground. Telegraph operators reported
being able to send messages even though the power was disconnected;
enough electricity was flowing through the lines to work the devices.
There's more. In 2012 the Sun blew out another blockbuster
that was in many ways the equal of the one in 1859, but happily for us
it was sent off in another direction, and missed the Earth. Had it hit
us, the huge flux of charged particles would have overloaded satellites.
Worse, the GIC would’ve caused widespread power failures and blackouts.
A much smaller solar storm in 1989 did just that in Quebec.
It’s not clear if the 774 and 993 events were that powerful or more;
it’s hard to scale these things without direct measurements. But the
astronomers who did the research estimate the 774 event (the more
powerful of the pair) was five times stronger than any solar storm seen
in the modern satellite era (starting in 1956) up to 2005.
I’ll admit, that’s scary. Our modern civilization depends on our
electronic devices, and those in turn depend on electricity and
satellites. A blast hitting the Earth from a storm as big as any of
those four historical events would be bad. Very bad. The 1989 power surge blew out huge transformers in North America, and these can take months to replace. Imagine months without electricity, and you start to get an idea of how disastrous this can be.
We don’t know how often the Sun throws a tantrum as large as these,
but clearly it’s done so at least four times in the past millennium or
so — probably more, since three of them hit the Earth, and we only knew
of the fourth due to our space-based astronomical assets. Statistically
speaking, most will miss us, so they’re likely more common than we
thought.
This is a threat we need to take very seriously. Unfortunately, it’s
extremely expensive to mitigate. Our power grid in the US was
constructed decades ago when our use of electricity was much lower. It
was designed with lots of spare room for more power flowing through it,
but over the years our appetite has grown, and the grid is currently
very nearly at capacity. Big spikes now can cripple huge areas.
We need to upgrade the grid, add more capacity, more capability to handle surges induced by solar storms. The good news is there are studies being done to see what we can do to prevent widespread blackouts, and NASA is on it as well. We also have eyes on the Sun, including NASA's Solar Dynamics Observatory, and scientists monitor "space weather" constantly.
By coincidence, just last night I read that the White House is looking into this situation pretty seriously,
and I'm very glad to hear it. A monster solar storm may be the biggest
and most immediate threat there is from space, but it’s one we can
handle if we’re prepared for it.
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