Astronomers determine the presence of specific elements in nebulae, including the Veil Nebula, by looking for specific wavelengths of light that each element produces. Each element emits or absorbs light at characteristic wavelengths, which can be detected through spectroscopy. By analyzing the light from the nebula, astronomers can identify the spectral lines corresponding to different elements, allowing them to map the distribution of oxygen, sulfur, hydrogen, and other elements in the nebula.
The following image is a picture of the Veil Nebula made by combining several photos taken by the Hubble orbiting telescope.
The colors in the picture indicate the different elements present: blue is oxygen, green is sulfur, and red is hydrogen.
How do astronomers know which element is present where?
by observing chemical reactions taking place in the nebula
by comparing the density of the gas to the densities of various elements
by looking for specific wavelengths of light that each element produces
by measuring the temperature of each part of the gas
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