The Sun’s Fate Will Be A Most Colorful Affair – Come See

ESO’s Very Large Telescope shows the glowing green planetary nebula IC 1295 surrounding a dim and dying star. It’s located about 3300 light-years away in the constellation of Scutum the Shield. Click to enlarge. Credit: ESO

Sure, comets are awesome, so are solar and lunar eclipses but for night to night sky watching pleasure, give me planetary nebulas. Like finding a prize in the bottom of a box of Cracker Jacks, I get a little thrill every time one comes into view in the telescope. Not only are they beautiful to look at, but I see the sun’s fate right in front of my eyes.

We see the white dwarf in the center of IC 1295 in this close-in view. White dwarfs are extremely hot when they first form – around 180,000 F or 18 times hotter than the sun – but they slowly cool over the age of the universe to become hypothetical black dwarfs. Credit: ESO

They’re called “planetary” because their circular and oval shapes reminded early astronomers of planets. “Nebula” means cloud as in a cloud of celestial gas and dust. Other than appearance, they have nothing to do with planets.

Abell 39, located 6,800 light years from Earth in the constellation Hercules, is one of the most spherical planetary nebulae known. Planetary shells expand outward and fade after some tens of thousands of years. Click to enlarge. Credit: WIYN/NOAO/NSF

Reminiscent of a chrysalis or cocoon, a planetary nebula is the cast-off atmosphere of a star like the sun. Exposed at its center is the former star’s core, now reborn as a tiny, Earth-sized object called a white dwarf star.

A selection of planetary nebulae photographed by the Hubble Space Telescope. Some show multiple shells from several episodes of strong winds blasting from the core through the outer layers of the stars. Credit: NASA / ESA

When a supergiant star runs out of fuel to burn in its core, it collapses and explodes as a supernova. Stars like our sun reach their golden years more gracefully by puffing their atmospheres into space like an aging Gandalf blowing smoke rings in the movie series The Lord of the Rings. The huff and puff comes from the final throes of fuel-burning in their cores as the stars settle into stable white dwarfs.

The Cat’s Eye nebula in the constellation Hydra in a photo made in both X-rays with the Chandra Telescope and in visible light with the Hubble Space Telescope. Credit: NASA/CXC/RIT/J.Kastner et al. (X-ray); NASA/STScI (optical):

During its life sun-mass stars burn hydrogen to create the heavier element helium. When that’s used up, the star’s core contracts and gets hotter – hot enough to burn helium into carbon. The increased heat produced by burning helium causes the star to expand into a red giant.  Five billion years from now, our sun may bloat up big enough to completely incinerate the inner planets including Earth.

Bigger stars can burn carbon and other even heavier elements. A sun-sized one stops at carbon and then expels its expansive outer atmosphere, exposing a tiny, dense, fiercely-hot core –  here at last we have our white dwarf.

White dwarfs with the mass of our sun are almost the same size as planet Earth. Since all that mass is packed into such a small object, white dwarfs are fantastically dense. A teaspoon of its matter would weigh 15 tons.

All that gas expelled into space fluoresces in the intensely energetic ultraviolet light pouring from the dwarf and glows like a neon sign in space advertising the final days of another star. Different elements in the shell glow different colors: green is prominent and comes from excited oxygen. Nitrogen and hydrogen provide brush strokes of red and helium blue.

Stars with masses like the sun and up to 8 times its mass will eventually evolve into planetary nebulae. Our middle-aged sun still has about 5 billion good years left before becoming a colorful balloon like IC1295 and its kin. Want to see more images of these gems? Click HERE.

9 Responses

  1. Roma

    So is the white dwarf the ‘last phase’ of a star’s life? Would it still radiate heat and light towards earth- in a more intense or a more diminished capacity? (Or I suppose earth would be destroyed anyways by the explosion) I am just curious as to what happens after it becomes a nebula- is it simply transformed or does it eventually fizzle out?

    1. astrobob

      Hi Roma,
      Yes, it’s the end for sun-like stars. The white dwarf is still very hot but very slowly cools over billions of years. The Earth would likely have been incinerated earlier when the sun expands into a red giant star prior to becoming a white dwarf.

  2. aravind

    HI bob,
    again bugging You.
    I wanted some good books or PDF’s or good websites on Stellar evolution which starts from basics to advance Please help me. Some how Stellar evolution is interesting for me.
    Aravind benaka.

      1. aravind

        thank you bob,

        in web u have so much of information we get lost and dnt knw where to start off so initially require your help. Also i will check with the book.


  3. Wayne Hawk

    Aloha Astro Bob!

    While reading your very informative blog about the “end days” of the suns (stars) of the universe, including our own, I was relieved to see you finally said (in the last paragraph) our sun still has 5 billion years left. Could you imagine the small “panic” you could have incited had you not said that one fact? Whew!

    I remember as a child thinking that our sun was the only thing around me that would “last forever”. Imagine my disappointment (and the inner horror) when I learned that that just wasn’t true! Then, later on to learn that absolutely EVERYTHING that we have known in our lives (and more) will eventually be gone was almost too much for a young person to grasp. It was a really difficult fact to accept, knowing that there was absolutely no place to escape to that would or could “last forever”.

    With the universe expanding (and in places, contracting) and all these suns “dying” and new ones being “born”, imagine what our “night sky” might look like in another 4.5 billion years. Just think if someone came to you with the ability to “time travel” and took you ahead that amount of time and put you on the earth where Duluth, MN. used to be with a powerful telescope…when you looked through it, how much of the evening sky would you find familiar? Would you even be able to identify ANY of it anymore?

    I don’t mean to get existential at all with this because the actual FACTS are enough to “blow ones mind” if you let them! It’s no wonder some folks hang on to the “creationist” theory rather than accept the “evolutionists”…it’s easier on ones mind! Heh-heh…

    You’ve written some fantastic thought provoking articles here, a cluster of them have been within the last couple weeks, Bob. I think this is the reason I keep reading your website. For a “man of science”, you like to delve into that “out of the box” kind/type of thinking, more so than what most folks have come to expect from such people. Keep up the great work and know that your efforts here are being well read by more people than you may realize (maybe you do).

    Thanks again Bob.

    1. astrobob

      Hi Wayne,
      I appreciate your thoughts and reflections on the future and share them. I’m guesstimating it might only take a couple hundred thousand years to “re-make” the sky’s constellations. Makes you appreciate the nanosecondness of life. And thanks once again for such a wonderful compliment on the blog. I’ll keep plugging away.

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