Cosmic ray
A farewell message across the universe
While you are reading this, you are bombarded by thousands of farewell messages that were sent by the stars that are galaxies away: cosmic rays.
Massive explosion of a star is where comsmic rays start their long journey. A star beyond a certain size collapses by its own mass when it reaches its end of life. In some cases, a degraded star may reach the temperature that triggers nuclear fusion, resulting in an explosion. That's what is known as supernova. In our galaxy, two supernova explosions occur every 100 years on average. Supernova unleashes a tremendous amount of energy to the universe, loading small particles such as protons and nuclei with extremely high energy and shooting them to the universe like a sling shot at the speed of light or even faster. They are cosmic rays.
A supernova explosion (SN 2013ej) observed at Messier 74 in the Pisces about 30 million LYs away.Imagine a massive star exploding in a remote corner of the vast universe hundreds of millions of years ago--just like a huge firework in the quiet corner of a night sky that nobody notices it.
These stars that end with supernova explosions are huge—and they are appropriately named as "Massive Stars." How 'massive' are they? The volume of the sun is about 1.3 million times larger than the volume of our planet, earth. But, massive stars are dozens to hundreds of times heavier than the sun. Despite the ‘massive’ presence of these stars, they have a lifetime of only millions of years. Of course, compared to humans, millions of years is a pretty long time, right? But in the scale of the universe, which has 13.8 billion years of age, massive stars are like tiny particles that flash on and off in the blink of an eye. Who would even notice that a massive star even existed once, after it explodes and vanishes into the vast universe?
But massive stars do not seem like the idea of disappearing unnoticed. They wish to let someone out there know of their existence and its end. But how? Massive stars do not know how to write, so that they send their own body in the form of cosmic rays across the universe. With cosmic rays, Massive Stars are saying:
I had a short but wonderful life. My body will soon burst into flames, but I have no regrets. Enclosed are tiny bits of myself as my farewell to the rest of the universe. Goodbye!
About 50 million LYs away in Virgo, NGC 5426 SupernovaAt the mement of explosion, the tiny particles of a massive star embark on their long and lonely journey to the dark and unknown space. After traveling for hundreds of millions of years, finally, a tiny little fraction of them miraculously reach the Blue Marble. What if it did not reach the Earth, and fell on Jupiter or Mars? Or what if it missed the solar system all together? Who would have even noticed the last moments of the Massive Stars who sent their bodies as their last farewell messages? Only if they enter into the Earth, and only if they are fortunate enough to fall into a 'cloud chamber' while someone is watching, they are able to finally deliver the farewell message.
Therefore, if you are fortunate enough to witness them at one point of your own journey, I believe that they deserve your kind words like:
Hey, you finally made it! How long and lonely was it to to travel across the universe, little fella? Job well done! And now you may rest in peace.
Tonight, if you have a chance to see the night sky, why don't you give the words of sympathy to the cosmic rays that just flung themselves to you to finally finish their long journey?
Stars Above Haleakala, Haleakala National Park, Maui, HI by Daintyheart (cc-by-2.0)What is the 'cloud chamber'?
The cosmic rays and their fragments generated from the collision with the atmospheric particles are too small to be seen in naked eyes. It's so small that they just penetrate our bodies. Fortunately, there are a few ways to detect them, one of which is a cloud chamber.
When charged particles pass between supersaturated alcohol vapors near the dew point, the surrounding particles become ionized, and the alcohol vapors are condensed instantaneously, leaving a white trace in place as the cosmic ray passes through. So the white trace is not a cosmic ray, but the condensed alcohol clouds showing the cosmic rays passing by. Even with a small cloud chamber, you can see countless cosmic rays and their fragments passing by. They are extremely fun to watch. I watched it for a couple of hours at the Exploratorium in San Francisco.
Cloud chamber can be made at home with only dry ice, alcohol, and water tank. Look at the link below.
Under a starry Santa Barbara sky:
Sangwon Suh
This is an English translation of my earlier posting originally written in Korean:
