What happens? Light is given off!! A light fingerprint is born.

Gotcha! Stellar Spectra
Give an astronomer a small trickle of light and the riddle will be solved. Science has decoded the Rosetta Stone of stellar spectra. The spectrum of a star tells us a great deal about such things as temperature, motion, composition and much more. A stellar spectra is like a "mug-shot, fingerprint, and DNA test" rolled up into one science.

De-Excitation
Electron moves down? – De-excitation. The technical term for the emission of a photon of light with energy and wavelength that corresponds to the energy difference between the energy levels the electron moved downward between.
 What happens? Light is given off!! A “light fingerprint” is born.

Hey there you cute atom, you! Ways to excite an atom into a higher energy state.
Absorption: We just talked about this above with the upward transitions of electrons. The atom can absorb light energy or photon. Only a photon with exactly the right amount of energy can move the electron from one level to another. If the photon has too much or too little energy the atom cannot absorb it.
Collisional Excitation – (bang!): An atom can become excited by a collision with another atom. If two (or more) atoms collide, one or both may have electrons knocked (physically) into a higher energy state. This happens very commonly in a hot gas where atoms move very rapidly and collide vigorously because of the hot temperature.

Absorption Spectra CreationThe electron in a lower energy state moves up to a higher energy state and absorbs light with energy that corresponds exactly to the specific energy difference between the two levels.