Astronomy
The Use of Spectroscopy to Determine Chemical Composition of Stars
Quick fact
The element helium was discovered in the Sun's spectrum before it was found on Earth—its name comes from the Greek word for the Sun, Helios.
Why this is interesting
You can never visit a star, yet astronomers know it's made of hydrogen, helium, and a pinch of iron. How? By borrowing a trick from a simple glass prism that splits sunlight into a rainbow—with hidden barcodes.