Most of us know that the sun is a giant ball of gas, but what exactly is it made of? Astronomers have been working on uncovering the sun's exact composition for many years, and this is the current theory...
Composite image of the sun on 9/7/2011 from the Solar Dynamics Observatory
Since different elements have different weights, we can talk about the solar composition in terms of weight. The sun weighs about 4*10^30 pounds (that's a 4 with 30 zeros after it!). About 74% of that mass is Hydrogen atoms, 25% of the mass is helium atoms, and 1% is a variety of other elements including oxygen, carbon, iron and others. Another way to think of the sun's composition is in terms of number of atoms (or volume, essentially). In these terms, 92% of the sun is filled with hydrogen atoms, about 7.8% is made of helium atoms, and that other tiny 0.2% is made of heavier elements. This composition is ever changing, as the sun is continually undergoing fusion of hydrogen into helium in its core. The sun is also shedding mass in solar wind and solar flares, but this amount is so small compared to the size of the sun that it's practically unnoticeable. Over a human lifetime the composition of the sun will stay pretty much constant.
So how did astronomers figure out what the sun is made of? Tune in later this week to find out!
Image courtesy of NASA/SDO and the AIA, EVE, and HMI science teams
