## Glossary -- K

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Kelvin scale
a temperature scale that directly scales with the random motion energy of a substance, such that 0 Kelvin is at absolute zero (state where all random motion ceases) and higher temperatures have non-zero Kelvin values. It scales like the metric system's Celsius scale for increasing temperatures---every degree interval of the Kelvin scale corresponds to the same change in the random motion energy as a degree interval of the Celsius scale: # Kelvin = # Celsius - 273.
Kepler's 1st law
orbits are ellipses with the central object at one focus (not the center!). There is nothing at the other focus.
Kepler's 2nd law
a line between the satellite and the central object sweeps out equal areas in equal intervals of time. A satellite moves faster when it is closer to the massive body it orbits and moves slower when farther from the massive object.
Kepler's 3rd law
for an object in an elliptical orbit around a massive body, the square of the orbital period is proportional to the cube of the average distance of the orbiting object from the massive body. The massive body's mass is proportional to the (average distance)3/(orbital period)2. In general, for two objects orbiting a common point between them, their combined mass is proportional to: (average distance between them)3/(their orbital period)2.
kilogram
unit of mass in the metric system.
kinetic energy
the energy something has because of its motion = 1/2×mass×velocity2.
Kuiper Belt
a disk of comets beyond Neptune's orbit (or 30 to 100+ A.U.) that orbit roughly in the same plane as the planets. Many of the short period comets come from the Kuiper Belt.

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last updated: 27 May 2001