The Venus emissions was measured in a narrow frequency range around 4.74 terahertz (black line), which corresponds to a wavelength of 63.2 micrometres. The atomic oxygen in Venus' atmosphere absorbs this radiation. This is comparable to the Fraunhofer lines in the solar spectrum, which give an indication of the atoms in the Sun's atmosphere. In the terahertz spectrum of Venus, an absorption line appears that is characteristic of atomic oxygen. The strength and shape of the absorption signal is a measure of the amount of atomic oxygen and its temperature.