Timeline for Where will the Goldilocks zone be when the Sun becomes a red giant?
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15 events
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| Nov 7, 2017 at 5:58 | comment | added | Chappo Hasn't Forgotten | @Nzall: the same stages as above are shown in the two charts in the answer by user154997, but they omit what happens after 11b years - presumably because only the stellar core remnant (the white dwarf) is left - and the timescale isn't as clear. I hope the above clarifies this for you. | |
| Nov 7, 2017 at 5:54 | comment | added | Chappo Hasn't Forgotten | @Nzall: this core is a white dwarf, it's about the size of the Earth but extremely dense (composed of electron-degenerate matter) with a temperature of over 100,000 K - but this is way too cold for nuclear fusion. Its faint luminosity comes from the emission of stored thermal energy - in other words, it glows rather than shines. It's no longer a star, it's a "stellar core remnant", but it's extremely stable and will continue to radiate energy - slowly cooling - for over 1,000,000 billion years. By comparison, the Universe itself is only 13.8 billion years old. | |
| Nov 7, 2017 at 5:40 | comment | added | Chappo Hasn't Forgotten | @Nzall: the chronology is: 0 yrs (Sun is formed); 4.6 billion yrs (now); 10b yrs (end of core hydrogen burning, exit from main sequence, starts sub-giant phase, expanding to double current size); 10.5b years (starts main red-giant-branch phase: rapid expansion to 200x current size); 11b yrs (end of shell hydrogen burning, helium flash starts core helium burning, horizontal branch phase: Sun shrinks to 10x current size); 11.08b yrs (asymptotic-giant-branch: rapid expansion, shell helium burning); 11.10b yrs (fuel exhausted, brief planetary nebula disperses leaving very hot carbon-oxygen core). | |
| Nov 3, 2017 at 18:52 | comment | added | Nzall | @Chappo So the Sun turns into a glowing ember which slowly cools down... and a planet that's nowhere near the habitable zone right now will end up in it 5 billion years after that happens? I'm not quite sure how the sun can become so much hotter over that period if it's going to turn into an ember at the start of that period. It's as if your fire pit in your back yard can set the tree in front of your house on fire 5 hours after it burned most of the wood ion the past 10 hours. | |
| Nov 3, 2017 at 11:20 | comment | added | Chappo Hasn't Forgotten | @Nzall so short answer is that the Sun spends a brief 11 billion years as a star, followed by 1000 billion years or more as a glowing ember. No bang. | |
| Nov 3, 2017 at 11:10 | comment | added | Chappo Hasn't Forgotten | The Sun will keep burning hydrogen and helium for another 5.5 billion years, until there's not enough left to maintain fusion reactions. At that point, the core is almost entirely made of carbon and oxygen (the "ashes" of helium burning), and collapses into a white-hot compact degenerate mass about the size of the Earth. Commonly known as a white dwarf, with a life in the order of trillions of years. | |
| Nov 3, 2017 at 10:40 | comment | added | Nzall | @Chappo regardless of whether it will go nova or not, the Sun is predicted to only last another 5 billion years. Or is that wrong too? And if so, how can Jupiter still be in the habitable zone another 5B years later? | |
| Nov 2, 2017 at 21:30 | comment | added | Chappo Hasn't Forgotten | @Nzall: our Sun won't go supernova, it's too small for type 2 and doesn't have a binary companion for type 1 (as a white dwarf). Common misconception. | |
| Oct 27, 2017 at 17:24 | comment | added | Motomotes | The thing is the model uncertainty is so laughable, the real answer is no one knows. Some newer models of star creation, such as electromagnetic confinement, purport that stars only undergo fusion on the surface. | |
| Oct 27, 2017 at 17:01 | comment | added | Dan Is Fiddling By Firelight | The times in the 2nd to last paragraph are from the suns birth not from present. | |
| Oct 27, 2017 at 15:45 | comment | added | Nzall | @ mattdm then how can Jupiter be in the habitable zone in 10 billion years if the sun will have gone nova by then? | |
| Oct 27, 2017 at 15:27 | comment | added | mattdm | @Nzall "giga-" is billion (10⁹) | |
| Oct 27, 2017 at 14:54 | comment | added | Nzall | Remind me: Is a Gyr 1 million years or 1 billion years? I thought it was billion years, but I thought the sun only had about 5 billion years left before the supernova? How can other planets then be in the life zone another 5 billion years after? | |
| Oct 27, 2017 at 9:27 | comment | added | user154997 | I thought there was first the red giant branch (RG), with luminosity reaching about 300 times current value, then the horizontal branch (HB), with luminosity constant at about 20 times, and then the asymptotic giant branch, which is what your consider. This would matter as during RG and HB some satellites of Jupiter or Saturn might be in the Habitable Zone. | |
| Oct 27, 2017 at 9:13 | history | answered | Anders Sandberg | CC BY-SA 3.0 |