How much do you know about our sun and how it works? A recent episode of Nova, on my local PBS station, very effectively demonstrated my own limited knowledge on the object that accounts for over 99% of the total mass in the Solar System.
99%! That’s just staggering. Everything else out there: planets, comets, asteroids, and perhaps Stephen Hawking, make up the remaining <1%.
Think hard about all of that mass crammed into a near perfect sphere that is roughly 109 times the diameter of Earth and you start to get a sense of the amount of energy the sun contains. I’m certain most people understand that the sun is an immense fusion reactor: gravity compresses 620 million metric tons of hydrogen atoms together, fusing them into helium every second at temperatures around 5500 Celsius. But how is the light made?
During the fusion reaction, high-energy photons (gamma rays) are released and are ejected outwards. These photons which collide with hydrogen and helium atoms comprise the ultra-dense plasma core. The core is so dense that it takes photons anywhere between 10,000 and 170,000 years to ricochet out to the next layer, the radiative zone. Here, where the plasma is less dense, it only takes the photons about a month to make it to the convective layer. From there they travel through the photosphere and are free to propagate into space.
Once beyond the sun’s gravitational and magnetic influence, it only takes an average of 8 minutes and 19 seconds for the photons to reach Earth. Throughout each stage of their lengthy and tumultuous journey, the energy of the photons is greatly reduced, yet still provides tremendous heat and energy after traveling 97 million miles at 186,000 miles per second.
So the next time you curse the sun as it blinds and roasts you or feel its warmth on your back or stop to observe it bathe a particularly bucolic scene with transcendent light, understand that that light might already be 100,000 years old. It’s actually a bit of a miracle when you think about it: too close to the sun, like Venus, and we’d be cooked, but too far away from it, like Mars, and we’d be frozen. We just happen to be on a pebble that’s the right distance from the sun’s fury and that’s about as incredible as it can get.
Photo credit: Justin Brown/Lam Partners