In most the field of astronomy, the periodic table is far simpler than the one you had to learn about in school. There are only three elements: hydrogen, helium, and metals. This does not mean that all of the other elements you know aren’t real, but because there is so much hydrogen and helium in our universe, they completely dwarf all of these other elements on large scales. In our entire solar system, the Sun comprises 99.86% of its total mass, and of that mass, about 98% of it is hydrogen and helium. Jupiter and Saturn alone make up 90% of what is left, and they too are made up of mostly hydrogen and helium. Virtually all of the other elements that make up basically everything you know are present in only trace amounts. The image below shows the relative abundances of all of the elements, and as you can see, most elements are too comparatively rare to even appear on the diagram.
Source: Wikipedia
Spherical Livestock 
This has always been one of the most fascinating and surprising things I’ve learned about astronomy. Looking around our world, with such diversity of materials, elements, and compounds, you would think that the rest of space would share the same composition. I love that it’s only through the interaction of the two simplest elements in incomprehensible quantities that we have any element seen on Earth
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Having taken Organic Chemistry in the past, I can attest to the fact that even interactions between a handful of elements can produce some of the most complicated and life-influencing reactions (and hardest to memorize!). It is absolutely incredible that our entire solar system is essentially made of two elements, hydrogen and helium. Your post definitely makes me realize that even though this course is making me much more aware of the diverse range of celestial bodies that make up our solar system, there exists a certain unifying beauty in the fact that the solar system was created through the interaction of two of our most simplest elements. Really great post!
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