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The Universe Within 12.5 Light Years

(www.atlasoftheuniverse.com)
266 points algorithmista | 2 comments | 05 Sep 25 22:20 UTC | HN request time: 0s | source
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jader201 ◴[06 Sep 25 01:47 UTC] No.45145848[source]▶
Tangential comment, but it’s crazy to think about how, when we look up at the stars in the sky, we’re seeing light in wildly varying degrees of age.

For example, when we look at the sun, that’s 8-minutes-old light. When we look at Polaris (the North Star), that light is 447 years old.

When we look at Andromeda?

Yeah, that light is 2.5 million years old.

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HardCodedBias ◴[06 Sep 25 01:50 UTC] No.45145857[source]▶
Nit: I think that the light from the sun is about 100k years old. Wild.
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aplummer ◴[06 Sep 25 01:55 UTC] No.45145887[source]▶
How can that make sense, the photons are emitted and fly straight at us
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1. siavosh ◴[06 Sep 25 02:05 UTC] No.45145942[source]▶
The photons were created a long time ago in the core. It takes thousand of years for it to reach the surface, and THEN it takes 8 minutes to get to us.
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2. greenbit ◴[06 Sep 25 13:30 UTC] No.45149114[source]▶
The photons created in the core are some seriously energetic gama rays. Sure, gama rays are very penetrating, but the solar core is dense, and it's about half a million miles to the surface, so these mostly get absorbed right there in the core, making stupendous amounts of heat. At any given depth that means that matter is going to re-emit photons, but never any more energetic than the original ones that are absorbed, but that radiation will be reabsorbed as well. That process of emission and reabsorption means that energy travels to the surface a lot slower than light in a vacuum, and sure, it takes a long time for that energy to reach the surface, but the photons that reach the earth are only the ones created close enough to the 'surface' to escape into space.