this post was submitted on 08 Feb 2024
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Have no fear, the sun will not explode. You need about 8 times the mass of the sun in order for a star to explode in a supernova. The sun will expand into a red giant when it finishes fusing hydrogen into helium. When this happens the earth might be swallowed up in the expansion. After the sun finishes burning helium and continues up the fusion chain to iron the fusion in the core will fail and the outer layers of the sun will puff off into a planetary nebula. This won't be a particularly violent event. The naked core leftover will be a white dwarf which is effectively just a molten ball of mostly carbon and oxygen gradually cooling off. It will take trillions of years to cool off.
Although, it's just a couple of hundreds of ~~thousands~~ millions of years before the sun ~~expansion~~ brightness makes Earth inhabitable. Not to make anyone freak out, but that's about 10 times less than 5 billions! Enjoy your life while you can!
Edit: sorry for writing mistakes at 2 am, see various sources below.
No, the expansion will start in about 5 billion years. The subgiant expansion phase will last for about 1 billion years. The earth may or may not be engulfed during the expansion as the best guess is the sun will expand to somewhere between venus and earth's orbit. The planet will be uninhabitable but again, the expansion won't start for about 5 billion years.
You're the second person in as many days that I've come across saying the red giant expansion phase will start in 500 million years. Where are you guys getting this info?
I may have confused expansion with brightness, it is increasing steadily and will make our planet inhabitable in that time frame. From astrophysist Paul M. Sutter https://www.space.com/solar-system-fate-when-sun-dies
That makes sense. I actually had to go look up to make sure I wasn't giving out wrong information since you were the second person. Maybe the other guy had read this article too. Glad we got it sorted. :)
I looked up more and found another source of worries with a slightly shorter deadline https://www.theguardian.com/science/2023/sep/25/supercontinent-could-make-earth-uninhabitable-in-250m-years-study-predicts
It's a few hundred million years, not a few hundred thousand, before the photosynthetic cycle is disrupted by silicate weathering from increased brightness.
Source?
Wikipedia has a summary:
"The luminosity of the Sun will steadily increase, causing a rise in the solar radiation reaching Earth and resulting in a higher rate of weathering of silicate minerals. This will affect the carbonate–silicate cycle, which will cause a decrease in the level of carbon dioxide in the atmosphere. In about 600 million years from now, the level of carbon dioxide will fall below the level needed to sustain C3 carbon fixation photosynthesis used by trees. Some plants use the C4 carbon fixation method to persist at carbon dioxide concentrations as low as ten parts per million. However, the long-term trend is for plant life to die off altogether. The extinction of plants will be the demise of almost all animal life since plants are the base of much of the animal food chain on Earth."
https://en.wikipedia.org/wiki/Future_of_Earth
It links to additional academic sources in the footnotes.
Oh, I thought I had written millions as in my source instead of thousands, I shouldn't write comments at 2 am, two mistakes. I didn't know about the silicate issue but the estimated remain consistant with my initial source.
Yeah, no worries. Hundreds of thousands of years would be very rapidly impending doom though!
What's interesting is that we're at about the halfway point in terms of complex life on Earth. The Cambrian Explosion happened about 538 million years ago and complex life likely has about the same time left. Interesting that humans happened to emerge right around the midpoint of that journey, and makes you wonder what kind of life will be around in the waning years.