Spectroscopy is probably the most important tool the scientist can use to find out more about our universe.
What is spectroscopy?
In its simplest form, spectroscopy is the measurement of light coming off of an object. We can graph this information in spectrum to make it easier for us to understand. Below is an example of a graphed spectra:
These dips and spikes happen at a certain wavelength. Because wavelengths correspond to color, we can visualize the data in a graph like this.
What causes these lines?
You may be wondering what exactly causes these dips, or those black lines in the rainbow spectra. The reason ties into atoms, and tells us why spectra are so important!
Three things are always in every atom: protons, electrons, and neutrons. Below you can see how they are arranged.
As you can see, the electrons orbit the nucleus in different “rings”. These electrons can skip up or down these rings if they receive a specific amount of energy. If the energy is too high or too low, the electron lets it pass.
Energy levels correspond to wavelengths, which correspond to colors! This means that the atoms are absorbing a specific color. Each atom has different ring energy requirements, which means that each atom absorbs different bands of light.
How is this useful?
Imagine that you are trying to find out what a gas cloud is made of. All you have to do is analyze the light going through that cloud. If there is a line missing, then you know that the corresponding element is in the cloud!
Another cool example is exoplanets. One of the biggest questions right now in science is if an exoplanet can support life. To find out this vital information, we need to know what is in that planet’s atmosphere. We can do this by simply analyzing the spectrum and seeing which lines are missing. Then we look at the light reflecting off the planet to see what the ground is made of. This type of spectrum is called an absorption spectrum because some light is being absorbed.
The emission spectrum
But what happens when an object is emitting light? We need something called an emissions spectrum.
Electrons can move up rings, but they can also move down. When this happens, a specific color of light is emitted. When we look at a star, we see only the bands of light that are emitted. These spectra look like this:
Spectra not only tells us what something is made of but also how far it is. This is measured through a concept called redshift. As you can see in the image below, when an object is moving towards us, the spectrum gets shifted towards blue, and when an object is moving away from us, the spectrum is shifted towards red.
From the graph shown below, we can conclude that redshift is strongly related to distance. This means that with a spectrum, we can see how far away an object is!
Spectroscopy is so incredibly cool because, given just the light coming off of an object, we can tell what that object is made of and how far away it is!
Do you have any cool facts about spectroscopy? Share them in the comments below!
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