The sun is made almost entirely of hydrogen and helium. Earth, on the other hand, is made mostly of oxygen packed into various compounds. So are its rocky planet neighbors. The giant planets, such as Jupiter and Saturn, have compositions more like the sun’s, but still are notably different from it.
Here’s the puzzle. The sun and planets formed at the same time from the same cloud of gas and dust. But the material that made the planets had a composition different from the sun’s. How did that happen? Read more.