orbital element bonpâr-e madâri Fr.: élément orbital Any of the six parameters needed to specify the → orbit of an object around a → primary body (such as a planet around the Sun or a satellite around the Earth) and give its position at any instant. Two of them define the size and the form of the orbit: → semi-major axis (a) and → eccentricity (e). Three angular values determine the orbit position in space: the → inclination (i) of the object's → orbital plane to the reference plane (such as the → ecliptic), the → longitude of ascending node (Ω), and the → argument of periapsis (ω). And finally the sixth element is the → time of periapsis passage which allows calculating the body's position along the orbit at any instant. |
osculating elements bonpârhâ-ye âbuseš Fr.: éléments orbitaux osculateurs The orbital elements of an osculating orbit. → osculating; → element. |
parent element bonpâr-e permâr Fr.: élément parent A radioactive element that spontaneously decays into a new substance. The product of this decay is known as a "daughter" element. |
platinum group element (PGE) bonpâr-e goruh-e pelâtin Fr.: élément du groupe du platine One of the six metals → platinum (Pt), → iridium (Ir), → osmium (Os), → palladium (Pd), → rhenium (Rh), and → ruthenium (Ru) that are grouped together in the → periodic table. They are relatively hard and resistant to corrosion and are used in jewellery and in some industrial applications. All are resistant to chemical attack. |
radioelement partow bonpâr Fr.: radioélément An element, such as uranium, whose isotopes are all radioactive. |
rare earth element bonpâr-e xâki-ye kamyâb, xâk-e kamyâb Fr.: terre rare Any of the group of metallic → chemical elements with → atomic numbers between 57 and 71 inclusive. The name is an inappropriate terminology, since they are neither rare nor earth; preferred name → lanthanide. |
siderophile element bonpâr-e âhandust Fr.: élément sidérophile In the → Goldschmidt classification, any → chemical element that has an → affinity to combine with → iron rather than some other element. These elements are concentrated in the → Earth's core. The group includes → iron (Fe), → nickle (Ni), → cobalt (Co), → platinum (Pt), → gold (Au), → tin (Zn), and → tantalum (Ta). The siderophile elements include → highly siderophile element (HSE). → siderophile; → element. |
trace element bonpâr-e malé Fr.: élément trace, oligo-élément Any → chemical element that is found in extremely small amounts, especially one used by organisms and held essential to maintain proper physical functioning. |
transuranium element bonpâr-e tarâ-urâniomi Fr.: élément transuranien An element beyond uranium in the periodic table, with atomic number greater than 92. Such elements do not occur in nature, but may be obtained by suitable nuclear reactions. They are all radioactive and members of the actinide group. |
volatile element bonpâr-e parrâ Fr.: élément volatile In → planetary science, any of a group of → chemical elements and → chemical compounds with relatively low → boiling points that are associated with a planet's or moon's → crust and/or → atmosphere. For example, H, He, C, N, O are underabundant (relative to the solar → photospheric values) in all types of → meteorites, including the C1 → carbonaceous chondrites. Any heating of the meteorite parent body subsequent to its formation would tend to drive the volatile elements out of the rock, whence it sublimated into → interplanetary medium. |