Atomic spectra line spectra7/2/2023 ![]() ![]() Notice how powerful a tool spectra can be. Each one of these lines represents where atoms in the solar atmosphere blocked a certain wavelength of light. The dark lines are called absorption lines. This is called an absorption spectrum, also known as a dark-line spectrum. So when astronomers analyze any one star’s spectrum, that continuous spectrum will have little gaps in it where those certain wavelengths got scattered. ![]() Stars have a surface layer and an atmosphere same as planets.Īnd when light passes through a star’s atmosphere, the atoms there will absorb a bit and scatter it so that it never reaches our telescopes.Įach atom on the periodic table scatters certain wavelengths of light. ![]() See, when a star emits light, that light has to pass through the gases of the star’s atmosphere. Astronomers rarely deal with continuous spectra-and they don’t tell us much, anyway. In astronomy, that object is usually going to be a star. You may not have seen it portrayed quite like this-you’re probably more used to seeing it as an arc through the sky after a rainstorm-but this probably isn’t unfamiliar.Ī continuous spectrum is produced when any object emits light. It’s your basic spectrum of the colors of the rainbow. We start with a continuous spectrum, the most basic kind of spectrum. So, what exactly is a spectrum, and how can we use it to analyze radiation from space and learn more about the universe? And it’s an astronomer’s most valuable tool. In astronomy, it means the wavelengths of electromagnetic radiation spread out so we can analyze them individually. Put these two bits of knowledge together, and astronomers now have everything they need to understand spectra (the plural for spectrum).Ī spectrum is something I’ve covered in previous posts. The Uncertainty Principle also provides a natural broadening of all spectral lines, with a natural width of Δν = ΔE/h ≈ 1/Δt where h is Planck’s constant, Δν is the width of the line, ΔE is the corresponding spread in energy, and t is the lifetime of the energy state (typically ~10 -8 seconds).Astronomers know that if white light passes through a prism and is bent, it’s separated out into its component colors-the colors of the rainbow.Īstronomers also know that when light interacts with atoms, the building blocks of the universe, the atoms absorb photons of light and reemit them-but in a different direction.
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