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Big, Bright, and Hot

Just wanted to point out how huge the Sun is. That’s all.

Me playing slide guitar in front of a bonfire. Photography by Ben Gilliom.

Indiana is hot today – really hot – maybe a record setter. News outlets are saying that in Colorado wild fires are crawling across mountains and consuming neighborhoods. The heat and fires have me thinking about something I often think about: how big and hot the Sun has to be for it to be this hot and bright here on Earth.

Being a country boy, I’ve attended a fair number of bonfires. Some of them have featured quite enormous, roaring fires. Yet, no matter how big the fires have been, the heat and light quickly drop off just yards away and the night remains dark, cold, and unaffected.

I haven’t measured this myself, but I’m told that on average the Earth orbits somewhere around 92,960,000 miles from the Sun. That’s a long way away (approximately 1 astronomical unit). The Sun is so far away that it takes about 8 minutes for the Sun’s light (which coincidentally travels at the speed of light 299,792,458 miles/second) to reach us here on Earth. So compared to the bonfires I’ve seen, I think about how big that burning ball of fire we call the Sun must be for it to be this hot and light out here. Amazing.

Even more amazing: compared to other stars in the Universe, the Sun isn’t even a very big star.

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