Comet (source code)
= Comet
{wiki}
A <comet> is a small astronomical body containing volatile material and solid grains, capable of becoming active when heated. Its <comet nucleus> is the compact reservoir. As volatile <ice> undergoes <sublimation>, escaping gas carries dust outward and can make a diffuse <cometary coma> and a <comet tail>.<Comet Facts by National Aeronautics and Space Administration>[Structure and activity: nucleus, heating, coma and the two tail components]{ref}
A <cometary dust tail> responds strongly to <radiation pressure>, whereas ionized gas couples to the <solar wind> and <magnetic fields>. The visible tail is therefore not simply an exhaust trail opposite the direction of travel. An inactive distant <comet> can lack a prominent tail. Its <Kepler orbit>, later <planetary scattering> and material loss together determine the observable history.
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