KIDS ASK! WHAT WILL HAPPEN WHEN THE SUN DIES?

A picture of a Red Giant Star with a unique spiral pattern.
ALMACC BY 4.0, via Wikimedia Commons

Here at High Touch High Tech, we teach a LOT of science, and the best part about it is feeding young scientists’ curiosity about this amazing world we live in!  Although our programs are jam packed with experiments, we always make time to let our young scientists ask us whatever questions they’ve always wanted to ask a scientist.   

In the coming weeks, we will be sharing a special series of articles answering some of the most frequent questions that come up from our young partners in science.  Our question this week is:

WHAT WILL HAPPEN WHEN THE SUN DIES?

Here at High Touch High Tech, we love talking about all the cool stuff that happens on our beautiful blue planet Earth, but we also love talking about SPACE!  From giant planets to fiery stars to mysterious black holes, space is a subject that always inspires wonder.  Our young astronomers love learning about the “life cycles” of stars, and how stars coalesce from giant, dusty nebulas, ignite, and eventually burn through all of their fuel, “dying” in a supernova full of the elements that make up our very own bodies!  It’s a wonderful thing to know that we are all made of stars, but when we teach about stars, there’s always a quiet moment of realization that our own sun, Sol, is a star too, and one day will come to the end of its “life” as the star that we see. That’s when someone usually asks the kinda-scary question: what will happen when our sun dies?

Our own star, Sol, center of our Solar System.

Well, science friends, there’s GOOD NEWS and there’s BAD NEWS.  Bad news first? OK: Sol will eventually run out of hydrogen and helium fuel, as all stars do.  When that happens, the results will be catastrophic and will probably destroy the earth.  Now the good news!  Scientists are sure that that time will be very, very far in the future, like several BILLIONS of years far.  So, it will not be a problem in our lifetimes.  We also believe by the time the sun does go out, with science on our side, humans, animals, and plants from the earth will be safely living on other planets. So even when the sun dies, the good things we love about earth will be able to go on, even if they are in a different place.  It’s OK to feel sad or scared about the idea that earth will come to an end. All scientists know that even though it’s a little scary, it’s also true that our universe is always changing, and nothing stays the same forever.  That’s just the way the universe works. The end of our sun is a normal, natural thing that is probably happening to several other stars right now, out there in space.  We hope it helps to know that it’s a scientific fact that the whole universe is always changing, but nothing is ever really lost forever. It just changes shape and becomes something new.

This is a picture of new young stars being created out of the supernovas of old stars, in a place called the Magellanic Cloud. Aren’t they beautiful?
X-ray: NASA/CXC/Univ. Potsdam/L. Oskinova, et al.; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech
, Public domain, via Wikimedia Commons

So, what will happen?  Astrophysicists, the awesome scientists who study stars, have observed many different kinds of stars going through many different kinds of changes.  When Astrophysicists observe stars, the color and size of the star can tell them about how old a star is, and how much fuel it still has.  There are many types of stars, with cool names like “Yellow Dwarf,” which are small and common, and “Red Supergiant,” which are huge, old, and very hot.  Our friend Sol is a Yellow Dwarf star, and is now about 4.5 billion years old.  Sol is currently halfway through its life as a star, which means that it still has plenty of hydrogen and helium fuel to keep shining for another 4.5 billion years.  But when that hydrogen and helium start to run out, Sol is going to change from a Yellow Dwarf into a Red Giant, and that’s when the trouble starts for Earth!

A scientific artist’s drawing of a Red Giant Star.
BaperookamoCC BY-SA 4.0, via Wikimedia Commons

When a star becomes a Red Giant, it means the star is running out of hydrogen and helium fuel in its center, and starts to collapse in on itself, getting smaller at first.  But, as the star collapses in, it actually pushes more fuel together and the star gets a kind of “second wind,” burning even hotter and puffing up to HUGE size.  When Sol becomes a super-hot Red Giant, it will become so big that it will probably swallow up the Inner Planets closest to the sun, our neighbors Mercury and Venus, and then… yup, you guessed it.  It’s coming for Earth.  Scientists are not sure whether the Earth will be completely swallowed up by the Red Giant Sol, or if it will be just burned so hot that nothing can live there anymore.  The Outer Planets that are further away, like Jupiter, Saturn, and Neptune, will be pushed even further away by all of this and will probably be OK.  Astrophysicists believe that some moons of Saturn, like Titan, actually hold water and could support life, so let’s imagine humans far in the future watching all of this happen from there!  Maybe there will even be Red Giant-Watching Parties all across the galaxies of space!

Yellow Dwarf Sol and the Inner and Outer Planets. The Earth is the third closest to Sol. Because it is so close, Earth will probably be swallowed up into Sol when it becomes a Red Giant.

Finally, after another long, long time, when all of its energy is burned up, Astrophysicists believe that Sol will probably shrink down and become a White Dwarf Star, a dense, heavy, star with very little fuel left, mostly made of all of the heavy elements like gold, zinc, and iron that are the byproducts of stars burning their hydrogen and helium.  A White Dwarf is sometimes called a “ghost star.” They have a dusty appearance because their gravity is so heavy, they pull in and disintegrate any asteroid or comet that comes near.  White Dwarf Sol won’t be very bright and any humans on Titan probably won’t be able to see it anymore, but hopefully, no matter where we humans go, we will always remember our old friend Sol.

A picture of White Dwarf Stars taken by the Hubble Telescope.

Sources and Further Information:

An Astrophysicist explains Sol’s changes clearly for you, short version: https://www.youtube.com/watch?v=gaOPDk8Xbgw

Sol’s changes by an Astronomer, longer version: https://www.youtube.com/watch?v=Pcwcsfy2FDc

Detailed explanation of the changes Sol will go through: https://www.universetoday.com/25669/the-sun-as-a-white-dwarf-star/

An excellent examination of mysterious White Dwarf Stars: https://astroengine.com/2009/03/19/what-will-happen-when-the-sun-turns-into-a-white-dwarf/

A WHOLE IMAX MOVIE about Sol and how its going out could affect earth! https://www.youtube.com/watch?v=bUwA610rnZg

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