Electron energy levels
Neon Spectrum: Dark lines are where electrons absorb photons
Most of us are probably familiar with the basic model of a person. You have a central nucleus containing protons and neutrons, with electrons orbiting the nucleus. A more accurate model, however, is to think of electrons not as objects orbiting the nucleus in a manner similar to the planets around the sun, but rather as a cloud of electrons. Electrons do not travel around the nucleus along a unique path. Rather, electrons exist in different energy levels. Electrons can jump from one energy level to another, either moving to a higher energy level or falling to a lower energy level. For an electron to move to a higher energy level, it must be hit by a particle of light called a photon. When a photon hits an electron, that electron will absorb the photon and its energy, allowing the electron to jump to a higher energy level. To drop to a lower energy level, that electron will emit the same photon back into space.
Interestingly, different atoms will have different electron energy levels. For example, hydrogen has different energy levels than oxygen. The different energy levels between atoms means that the photons emitted by their electrons will all have different amounts of energy. So, depending on the energy of the photon, we can determine which atoms emitted those photons. Using what’s called a spectroscope, scientists can split a beam of light into its component colors and analyze those colors for any dark bands. The dark zones are where electrons absorb photons, allowing scientists to determine which types of atoms absorb those photons.
What objects can we see the composition?
The spectrum of the sun is used to determine its composition
Stars are the primary sources of light in the universe, and so spectroscopy generally involves starlight in one way or another. When a star emits light, that light must pass through the star’s atmosphere. Atoms in the atmosphere will absorb and emit the star’s photons, allowing astronomers to determine the star’s composition. In addition, some types of nebulae emit their own light, allowing scientists to determine their composition as well. Perhaps one of the most interesting applications of spectroscopy is the analysis of planetary atmospheres. As planets pass in front of their star, light from that star must pass through the planet’s atmosphere. The star’s photons will be absorbed by atoms in the planet’s atmosphere and then emitted back into space. Here on Earth, we can capture these photons in a spectroscope and determine the composition of the planet’s atmosphere. As this technology develops, we may soon be able to search for signs of life in the atmospheres of other planets.
Aidan Remple July 2, 2022 in Science
