Do Suns have Three Lives?
Main Sequence, Red Giant, White Dwarf
In very broad terms, those are stages our Sun will evolve through as it ages and dies. The end won’t commence for 4 or 5 billion years, so we don’t need to panic.
(In Part 1, I described how we have been using a bowling ball as a model of the Sun making scale models of the planets, and a scale model of the solar system.)
In 2008 when I came to teach at High Point University, we did the Solar system walk every semester, and during one of my Labs last semester (Fall of 2015) we got to Jupiter and turned around to look at the blue bowling ball, 142 million miles away in space, and 134 yards in our scale model.
Our sun was gone! GONE! There was no blue bowling ball where we left it! What happened? Who took it? Students ran back to the site of the mystery and found no trace. Oh my! My blue bowling ball is gone! Over the years and sharing with so many students I had felt a connection to that scarred orb, that blue bowling ball with a really big flat spot. Now it was gone.
Our Sun will leave the main sequence one day and become a giant, possible engulfing the Earth. The Sun we knew will be gone, too.
So now, years later, I went back to the Brunswick Lanes and asked for another used bowing ball. The generous folks gave me a shiny green ball with more than it’s share of scratches and cuts. We’ll use the new green ball during the Spring 2016 semester.
The red giant that is our future Sun will be fusing hydrogen into helium in a shell around the carbon and oxygen core, so its outer atmosphere will be pushed outward.
The Sun will be losing matter for millions of years as the solar wind becomes stronger. Millions of years is not a long time in the life of a star. When the hotter layers of the Sun become exposed, the radiation makes the rings of expelled matter glow. Our Sun would create a planetary nebula.
So this semester (Spring 2016) we use the shiny green bowling ball as our model for the Sun; we make our clay models of the planets, then we finally go outside to make our Solar system model.
Tuesday, all 3 Labs stepped off the trek to Jupiter and all went well. Someone suggested I put a sign on the shiny green bowling ball so it won’t be accidentally taken. Good idea! I remember to put the sign on the sun for my first Thursday Lab. Everything went well. The second Thursday Lab I forgot to put the sign on the shiny green bowling ball.
When we get to Jupiter and turn to look at the shiny green bowling ball model of our Sun, it was gone! GONE! AGAIN!! The sun is gone! Just as the mass-loss phase will be a relatively short time, the appearance of the shiny green bowling ball was for a very short time.
After the Sun becomes a giant and exhibits a planetary nebula, the remaining core will slowly cool off, converting gravity energy into heat energy, creating a White Dwarf. This stage will last billions of years more. The left-over star will slowly shrink and cool until it’s just a cold, dark clump. At this time, our galaxy is too young to have any of these Black Dwarfs.
So late in March the generous folks at Brunswick Lanes gave me another used bowling ball. I’ve already attached some more-permanent stickers to this new model with the request to not mess with it. Like the White Dwarfs that will be with us for billions of years, I hope this new sun stays with us many semesters.