But eventually, our sun will give up the struggle, shrugging off its outer atmosphere in a series of outbursts that leave behind the star's core: a white-hot lump of carbon and oxygen. This white dwarf will initially be staggeringly hot, blasting off X-ray radiation that can do brutal damage to life as we know it. But within a billion years or so, the white dwarf will settle down to more manageable temperatures and simply hang out for trillions upon trillions of years.
That dim white dwarf will host a new habitable zone, but because the former sun will be so cool, that zone would be incredibly close, much closer than Mercury orbits our sun today. At that distance, any planet or planetary core would be vulnerable to tidal disruption — a pretty way of saying the gravity of the white dwarf could inadvertently rip a planet to shreds. Learn more by listening to the episode "Can planets survive the death of their star?
Thanks to Guy R. Paul M. Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community space.
Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in , and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe, to the earliest moments of the Big Bang, to the hunt for the first stars.
The study was published in the journal Nature. What will happen after the sun dies? An artist's impression of a planet right orbiting a white dwarf star. Keck Observatory. Scientists identify 29 planets where aliens could observe Earth. Read more. Quick Guide How to get the latest news from Guardian Australia Show Email: sign up for our daily morning briefing newsletter App: download the free app and never miss the biggest stories, or get our weekend edition for a curated selection of the week's best stories Social: follow us on YouTube , Facebook , Instagram , Twitter or TikTok Podcast: listen to our daily episodes on Apple Podcasts , Spotify or search "Full Story" in your favourite app.
When the core can no longer hold out, hydrogen from those outer layers will flood in and heat up—giving the sun more fuel to fuse. All will seem well. But this will come at a cost. The side effects of these events will cause the sun to redden, cool, and inflate to more than a hundred times its current size, swallowing the orbits of Mercury, Venus, and even Earth.
The sun will transform into a red giant, just like the stars Arcturus or Aldebaran that we can see in our sky. When the sun begins to fuse helium, it might seem a return to normal.
The helium will partly rebuild the ruins of the core, and the bloated star will lose much of its size. Planets' orbits around the sun will slowly expand.
It won't happen fast enough to save the Earth, but if Neptune edges far enough out it could become a home for humans, with some terraforming. Eventually, though, the hydrogen in the sun's outer core will get depleted, and the sun will start to collapse once again, triggering another cycle of fusion. For about 2 billion years the sun will fuse helium into carbon and some oxygen, but there's less energy in those reactions. Once the last bits of helium turn into heavier elements, there's no more radiant energy to keep the sun puffed up against it's own weight.
The core will shrink into a white dwarf. The distended sun's outer layers are only weakly bound to the core because they are so far away from it, so when the core collapses it will leave the outer layers of its atmosphere behind.
The result is a planetary nebula. Since white dwarfs are heated by compression rather than fusion, initially they are quite hot — surface temperatures can reach 50, degrees Fahrenheit nearly 28, degrees Celsius — and they illuminate the slowly expanding gas in the nebula.
So any alien astronomers billions of years in the future might see something like the Ring Nebula in Lyra where the sun once shone. Follow Life's Little Mysteries on Twitter llmysteries. Live Science. Jesse Emspak.
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