We could even build on that, and say that the thin disk is where all the youngest stars are found. We could say that within the thin disk are spiral arms, where the star formation actually happens. We could say that the oldest stars are found in the central bulge and the halo, where there is very little dust and gas to make new stars.
But…what about its chemical composition? If we could explore our galaxy and bring home test tubes of “star stuff,” what would we find? And what can that tell us about our galaxy’s history?
Meet the planetary nebula, one of the universe’s most gorgeous phenomena.
If you’ve ever looked through a telescope, you may have seen one of these before. Through a small telescope, one might look like a little planet—hence the name. But make no mistake, these nebulae have nothing to do with planets, and everything to do with stars.
Then, as the star runs out of helium fuel in its core, it expands into a giant a second time. This is the last time a medium-mass star will expand. It’s also the end of the line for the fuel in its core, since it can’t get hot enough to fuse carbon.
At this point, the star is so big that gravity at the surface is too weak to hold onto its atmosphere, especially in the face of the superwind of radiation pressure from the still-collapsing core.
The result is a planetary nebula…but what exactly is a planetary nebula? What is it made of? Why does it look the way it does?
Take a wild guess: how much energy do you think the sun generates?
Think about it. It definitely generates enough energy to power a world.
Humans depend on the photosynthesis of plants, which converts sunlight into energy. And that’s not all. Without energy from the sun, our atmosphere would behave very differently, and so would our oceans.
Everything that moves on Planet Earth does so because it has energy. And a lot of that energy comes from the sun. It doesn’t even stop there—obviously, the sun has plenty of energy to spare, if the recent influx of solar power means anything.
The sun is incredibly powerful. And it’s powerful enough to keep generating that kind of massive energy supply for billions of years.
If this quote really is from Cecilia Payne, then she had the right idea—at least for a female astronomer in the 1920s. Women in science back then faced an uphill battle to get recognized for any discoveries they made, and Payne was no different.
What’s so special about Payne, you might ask? Well, she wasn’t just one of the many “unsung heroes” of modern science. She was the one who figured out what stars are made of.
Yeah, that’s right. She sent a probe to the sun, collected a jar of star stuff, and brought it back to her laboratory…
Um, no, not really. It wasn’t that easy.
In fact, it was very difficult. She had far too many roadblocks than were fair. But she wasn’t out for money or recognition. She was just in it for the science. And science was what she got…