1000 Things You Didn’t Know About the Universe #5: Seeing Aurora Means the Sun Isn’t Killing You

Welcome to a new series of posts that will characterize 1000 amazing facts about the Universe.  There is so much out there that we have yet to learn, and every day, astronomers across the globe are using their research to reveal the deepest secrets of the cosmos.  This series will look at the strangest, coolest, most exciting facts that we have discovered in hundreds of years of modern science.

Fact #5:When you see an aurora in the sky, it is a sign that you are being protected by the Earth and not being blasted with solar radiation.

The Sun; A nourishing, warm, life giving, awe-inspiring, fiery ball of dangerous radiation, deadly plasma, and hellish fire that could melt your skin off! It’s true, the Sun is dangerous.  So why don’t we get more than a bad sunburn if we’re out in the Sun for too long? Are we some kind of super-evolved species? Hah fat chance.  We just have a layer of protection from our home planet.

The Sun, a 400 Million Million Million Million Watt Lightbulb

Why would the Sun try to kill us? Without it’s nourishing energy, life could never have started in the first place.  Well, the Sun is a giant spinning ball of fire.  It’s not gas, liquid, or solid, but a fourth state of matter, an electrically neutral medium of unbound positive and negative particles called plasma.  Plasma is neutral but conductive, meaning it responds to electromagnetic fields.  And because the hot upper layer of the Sun has convective currents that move charge, it generates a huge magnetic field.

Okay so the Sun is a magnet, so what?

Well, as the Sun rotates, these magnetic fields are twisted and intertwine with each other, and end up forming knots, called Sunspots.  Occasionally, the twisting and complex interactions of fields in the Sun result in a sunspot releasing a huge amount of charged particles (mostly fast moving protons) into space.  This is exactly the same as the solar wind released in all directions by the
Sun, it’s just much more powerful and concentrated.  Sometimes these blasts point straight at Earth like a gunshot.  These charged particles can mostly pass through your body, but tend to collide with some of the atoms in your DNA.  Like a particle collider, the smashing of atoms results in formation of other particles and energetic photons.  Radiation can destroy the DNA of your cells, causing mutations and other nasty problems, like Cancer.  It’s incredibly painful to have radiation poisoning.  You don’t want it.

So why can life survive and evolve without being cooked occasionally?  Because we are protected by our good friend and home planet, the Earth!

The Earth. Taken by a space robot.

The Earth has a magnetic field too.  It’s definitely not as strong as the Sun’s, but it does exactly what it needs to do.  The Earth has a magnetic North and South pole, and the field extends far out into space.  When incoming radiation from the Sun hits the Earth’s magnetic field, it’s trajectory is changed as it is shifted up or down along the field around the Earth past the magnetic poles.  Some of the particles are trapped in what are known as the Van Allen radiation belts, where they ionize the gases in Earth’s atmosphere, producing a lovely flash of visible light that we call Aurora.  Once this happens, they are gone and the danger has ended.

Earth’s magnetic field funnels the Sun’s radiation. Credit: ESA

The aurora is the result of the Earth’s magnetic field rendering the solar radiation harmless.  More solar radiation = brighter aurora.  This is why we constantly monitor the Sun to see when strong blasts of solar wind are coming our way.  We can predict aurora 36 hours before they happen because this is how long it takes the charged particles from the Sun to travel the 150 Million Kilometers to Earth.

What about places like Mars? Mars used to have a magnetic field, but it no longer does since it’s core has solidified.  When it lost that field, the heavy hitting solar particles ran into Martian water molecules and sent them flying off into space, which is why Mars has less water now than it did a few hundred million years ago.  Maybe there was life on Mars that was blasted into extinction when this happened. As far as we know, above ground life cannot survive without the protection of a planetary magnetic field.  I say above ground because the solar radiation can’t penetrate far underground, so if there is life on Mars, it will likely be living deep down below the surface, where we haven’t looked yet.

I always tell people “every time you see an aurora, it means the Sun has failed to kill you.” So make sure you go see an aurora, and thank the Earth for keeping you alive and not subjecting you to a horrible burning radiation death.

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