The topic of the day is main sequence stars, referring to stars that appear in a certain band on diagrams that plot stellar luminosity against stellar color (the Hertzsprung-Russell diagram being the most commonly used of these). Anyone who took even a cursory interest in astronomy back in their high school / middle school days will know that the vast majority of stars in our sky at any given time are main sequence stars, and that all stars spend the majority of their lives in the main sequence. Our sun is a main sequence star, and it will remain there for roughly another five billion years, which is when it will go red giant and most likely swallow up the four inner planets.
I do have to say here that I've always been (rather irrationally) a bit disappointed that our sun is "merely" a yellow dwarf. While the fact that it will eventually become a red giant assuaged my feelings a little, I've always been a bit saddened that the sun will eventually dwindle into a white dwarf and, in some hoary far-flung future, die that truly final death - the death with no further shore - in becoming a cold, invisible black dwarf. When I was much younger, I was tantalized by stories of those hot, bright, massive stars that would expand into the red and blue supergiants, the stellar heavyweights of the cosmos. I felt like they were the cool kids of the galaxy, the ones who would eventually explode in a unimaginable cataclysm of fire and light before collapsing - coming into their own, really - into even more fantastic stellar objects. Even among these upper crust members of sidereal society, however, there was a degree of stratification. The ones that became neutron stars were all well and good, like the kids who achieved success but still looked wistfully out at the things they might have wanted to achieve. The truly rare ones, however - those annoying kids that were good looking and smart and came from well-to-do families and whom you couldn't even hate because they were just that likable - they collapsed into the fabled black holes. Ah, the black hole. The ultimate celestial object. How often I wished that our own sun would somehow surpass its own physical limitations - leapfrog, as it were, through sheer force of will to become a blue supergiant even though everyone thought it would never amount to anything more than a red giant. "Look at me!" it would say, "I did it! You all thought I couldn't, but with just a little perseverance and hard work, I did it!" And then it would go supernova and collapse into a black hole and live happily ever after.
Yes, I just turned the universe into a bad 1980's family movie.
More realistically, it's a good thing that our sun is a yellow dwarf. Anything more and the Earth would probably wouldn't even be a barren ball of iron and rock, much less a staging ground for intelligent life. Going on with the metaphor, although the sun is quite plain by astronomical standards, it's very mild-mannered and nurturing - average, perhaps a little boring, but ultimately stable in the long-term. The supergiants might be the celebrities and rock stars of the universe, but they also live brief, tumultuous lives filled with violence, ending up as mere flickers of their former selves or as hungry, all-consuming vortices of endless need and ultimate destructiveness. The sort of lives that stars like the sun look at and go, "Oh my. I'm sure glad I'm not a giant hungry tear in space-time."
So as I grow more mature, I become more cognizant of what a blessing it is that our sun is "merely" a main sequence yellow dwarf. Being one of the cool kids isn't always what it's cracked up to be.
And I just totally grabbed that metaphor and jumped ship with it to Tahiti.
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