An Etymological Dictionary of Astronomy and Astrophysics
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A very → metal-rich star whose iron → metallicity, [Fe/H], exceeds 0.20 → dex. Examples include HD 32147, HD 121370, and HD 145675 (Feltzing & Gonzalez, 2001, A&A 367, 253).

→ super-; → metal; → rich; → star.

The property of some crystals of exhibiting three different colors when viewed from three different directions under white lights. → dichroism.

From Gk. tri- "three" + chroic, from chroma "color" + -ism.

Sefâmi, from se, → three, + fâm "color," + -i noun suffix.

The process by which the percentage of → fissile uranium in a sample is increased. Uranium obtained from mining contains several → isotopes of uranium in different compositions, such as U-238 (~99%), U-235 (~0.7%), and U-234 (~0.02%). Among them, U-235 is the only one that is fissile, i.e. can be used in a → nuclear reactor to produce heat (and consequently electricity) in a controlled manner. As such, the concentration of U-235 as a fuel used in a reactor needs to be increased, which is done using several techniques, such as → gaseous diffusion.

→ uranium; → enrichment.