What Can Spectroscopy Tell Us?

Atom or Molecular Fingerprints Every atom or molecule exists in its own unique energy state. This energy state is dependent on the surrounding electron configuration. The energy state can be increased (an electron moves to a higher energy level) by absorbing a photon (a particle of light) or decreased by emitting a photon. The energy of an absorbed or emitted photon is dependent on the discrete energy levels of the atom or molecule. This produces a characteristic spectrum that acts as a fingerprint and allows us to use spectroscopy to discover from what things are made. Go to this interactive to play with an atom.Go to this interactive to play with an atom.

How do we use this information? We can use this information to determine the composition of distant objects in the sky, such as galaxies, stars, planets, and nebula. By using spectroscopy we can determine what elements are present in the atmosphere of a distant planet. We are also able to determine the relative abundance of each element. In other words, it is possible to tell how much of each element there is relative to another.

Stellar Absorption and determining Composition

Click on the links below to find the periodic table of elements and their respective absorption and emission spectra in the visible portion of the spectrum. This is a spectrum of the Sun. The dark bands are called absorption lines and indicate different atoms present in the outer cooler layers of the Sun. The pattern of the absorption lines allows astronomers to determine the types of atoms and molecules that make up the star.

We can also learn about the motion of objects in space Astronomers can use the Doppler shift to determine how fast a star is moving towards or away from the Earth. By measuring the amount that the spectra lines are shifted, we can determine how fast the Earth and a star is approaching or receding from one another.

We can determine the temperature The light emitted by a star can be used to determine its surface temperature. Hotter objects have spectra that peak at bluer wavelengths while cooler objects have spectra that peak at redder wavelengths. Click on the Icon below to explore blackbody radiation.