Glossary Kk

KAKANGARIITE - Member of a rare group of chondrites, group K, named for their type specimen, the Kakangari meteorite that fell in Tamil Nadu, India, in 1890. Only three specimens are known with a total mass of less than 0.4 kg, all of which are rich in troilite, and show numerous primitive, armored chondrules. Unique in their chemical composition and with an oxygen-isotopic signature that distinguishes them from all other chondrites, K chondrites are thought to have originated in a small, primitive parent body that has yet to be identified.

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KAMACITE - Commoner of two Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt. % Ni, and forms large crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word for "beam."

KELVIN - Temperature unit equal to 1° C and 1.8° F; the absolute temperature scale defined so that 0 K is absolute zero.

KEPLER'S LAWS - Three laws of planetary motion discovered by Johann Kepler. (1) Planets orbit on ellipses with the Sun at one of the focii of the ellipse. (2) Equal area is swept out by a planet’s motion as it moves around the ellipse (a planet moves fastest when it is nearest the Sun).

Image source: Figure 2.2, Introduction to Modern Astrophysics, 2nd ed., Carroll & Ostlie, 2006.

(3) Where P stands for the period of the orbit (in years) and a is the size of the semimajor axis of the ellipse (in AU):

Image source: Figure 2.3, Introduction to Modern Astrophysics, 2nd ed., Carroll & Ostlie, 2006.

KILOGRAM - Fundamental unit of mass, which is the only unit still maintained by a physical artifact: a platinum-iridium bar kept in the International Bureau of Weights and Measures at Sevres, France. There is an ongoing effort to introduce a new definition for the kilogram by way of fundamental or atomic constants.

KINETIC ENERGY - Energy associated with macroscopic motion. In nonrelativistic physics the kinetic energy is:

KINETICS - Study of the rates of chemical reactions. The product which is formed the quickest is referred to as the kinetic product. The kinetic product need not be the most thermodynamically stable product. When a kinetic product is not the thermodynamic product, it is termed "metastable" and will eventually convert to the more stable form given sufficient energy and time.

KIRKWOOD GAPS - Asteroid-free gaps in the asteroid belt where asteroids have orbital periods that are a fraction of Jupiter's. Jupiter pulls asteroids out of these resonant orbits and produces the gaps.

KREEP - Lunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus (P), thorium, and other incompatible elements. These elements are not incorporated into common rock-forming minerals during magma crystallization, and become enriched in the residual magma and the rocks that ultimately crystallize from it.

KUIPER BELT - Region in the outer solar system beyond Neptune's orbit that contains billions of small, icy planetesimals from the original protoplanetary disc that failed to coalesce into planets. Kuiper Belt extends from orbit of Neptune to ~55 AU. It is ~20x wider and 20-200x more massive than the asteroid belt and contains three categories of bodies: classical KBOs, scattered KBOs (KBOs thrown into long elliptical orbits by Neptune), and resonant KBOs (in a 3:2 resonance relationship with Neptune including Pluto and sometimes called 'plutinos'). The Kuiper belt is sometimes considered part of the Oort Cloud.

KUIPER BELT OBJECT (KBO) - Generally, small bodies found in the Kuiper Belt; the largest, Eris, is <3000 km in diameter.

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