Atmosphere of Earth (see the temperature section, below). Because the general pattern of the temperature/altitude profile is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided (called atmospheric stratification) into five main layers. Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. From highest to lowest, the five main layers are: The exosphere is the outermost layer of Earth's atmosphere (i.e. the upper limit of the atmosphere). It extends from the exobase, which is located at
Elongation (astronomy) a moon of another planet from its central planet, for instance the angular distance of Io from Jupiter. Here we can also talk about "greatest eastern elongation" and "greatest western elongation". In the case of the moons of Uranus, one often talks about "greatest northern elongation" and "greatest southern elongation" instead, due to the very high inclination of Uranus' axis of rotation.. Elongation (astronomy) In astronomy, a planet's elongation is the angular separation between the Sun and the planet, with Earth as the reference point. The greatest elongation of a given inferior planet occurs when this planet’s position, in its