Солнечная система и ее тайны

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Spectroscopy

We mentioned that we can detect different chemicals in space because of the light that they absorb. Let's examine this in more detail. The more we understand about this phenomenon, the better we will be able to survey distant worlds for signs of life.

Every element has a specific set of colors of light that it absorbs. You may hear about an "absorption spectrum" or an "emission spectrum." because hot gases (such as in a candle flame) can emit light in addition to absorbing it. Since the same colors appear in both spectra, we will not be careful with our terminology, and just say "spectrum."

What makes each element different? Why does each have a unique spectrum even though many of them are the same color to our eyes?

Every atom, as you have heard, is composed of protons, neutrons, and electrons. The protons and neutrons are at the center, and the electrons form a unique arrangement around the outside of the atom. You can see a few examples below

Each electron has its own energy level, with many other energy levels available. The electrons can jump between these levels by absorbing or releasing energy. If the gap between energy levels matches the light perfectly, an electron may absorb the light. If not, the light will pass straight through.

Roll your mouse over (or tap on) the periodic table below to see the spectra of various common elements.

Colors of Light

When we talk about atomic spectra, the word "color" is used in a broad sense. The colors in the table above are in the visible range, but most elements also give off light in the infrared or ultraviolet ranges, outside our normal vision range. The terms "color," "frequency," "energy," and "wavelength" are all closely related in light. They can all be used to distinguish two kinds of light from one another.

Looking closely at exactly which colors of light are absorbed by an atom will tell us what energy levels are present in the atom. Because each element's atoms have a unique arrangement of energy levels, this will tell us what elements are present in an interstellar cloud, or in a planetary atmosphere.

Why does this matter? It matters because the composition of a planetary atmosphere would include the biosignatures we discussed in the Signatures of Life section! These lines of color are actually the first indication we will see that a planet has life.

Солнечная система и ее тайны