An Etymological Dictionary of Astronomy and Astrophysics
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A prehistoric period during which the main material used to make tools and weapons was stone. The Stone Age is usually divided into three separate periods (Paleolithic Period, Mesolithic Period, and Neolithic Period) based on the degree of sophistication in the fashioning and use of tools. The Paleolithic time period is by far the longest, beginning some two million years ago and ending around 10,000 BC to coincide with the end of the last ice age (Pleistocene epoch).

→ stone; → age.

A meteorite composed largely of rock-forming (→ silicate) → minerals. Stony meteorites are the most abundant kind, about 95%, of all meteorites. They are divided into two groups: → chondrites and → achondrites.

→ stone; → meteorite.

Meteorites comprised of roughly equal amounts of → nickel/→ iron and → stone. They are divided into two groups: → pallasites and → mesosiderites. The stony-irons are thought to have formed at the core/mantle boundary of their parent bodies. The stony-irons account for less than 2% of all known meteorites. Also called → siderolite.

→ stony; → iron; → meteorite.

→ occlusive consonant.

→ stop; → consonant.

A data center dedicated to the collection and worldwide distribution of astronomical data and related information. It is located at the Strasbourg Astronomical Observatory, France. The CDS has several goals, mainly: collecting all of the useful information regarding astronomical objects in computerized form, including observational data produced by observatories on the ground or in space; upgrading these data by critical evaluations and comparisons; and distributing the results to the astronomical community. Currently the CDS services include: → SIMBAD, Aladin interactive sky atlas, and VizieR catalogues.

CDS, short for Centre de Données astronomiques de Strasbourg.

A layered structure of sedimentary rocks in which the individual layers can be traced a considerable distance. The layers can be caused by many differences which include materials of different composition, color, grain size or orientation.

Strati-, from → stratum + -fication from L. -ficare "to do, make."

Ciné, → stratum + bandi, from bastan "to bind, shut; to contract, get, acquire; to coagulate," (Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind, → band).

A partnership of NASA and the German Aerospace Center, consisting of an extensively modified Boeing 747SP aircraft carrying a reflecting telescope with an effective diameter of 2.5 m. NASA Ames Research Center manages SOFIA's science and mission operations in cooperation with the Universities Space Research Association and the German SOFIA Institute. SOFIA is the largest airborne observatory in the world, with a planned 20-year lifetime.

→ stratospheric; → observatory; → infrared; → astronomy.

Having an intense, powerful, or vivid effect.
→ strong anthropic principle, → strong arm spiral galaxy, → strong encounter, → strong force, → strong gravitational lensing, → strong interaction, → strong lensing.

O.E. strang "physically powerful, powerful in effect, forceful;" cf. O.N. strangr "strong," Du. streng "strict, rigorous," O.H.G. strang "strong, bold, hard," Ger. streng "strict, rigorous."

Sotorg "large, strong," Mid.Pers. sturg "fierce; gross, coarse," Av. stūra- "strong, large, rough," stāuuišta- "strongest, biggest," cf. Skt. sthūrá- "strong, big, massy, thick," Gk. stylos "column, pillar," M.L.G. stūr "big, strong, coarse."
Zurmand, from zur, → strength, + -mand possession suffix.
Nirumand, from niru, → force + -mand possession suffix.

A version of the → anthropic principle that claims that the → Universe must be suitable for the formation of → intelligent life at some point. Compared with the → weak anthropic principle, this version is very controversial. Its implications are highly speculative from a scientific viewpoint.

→ strong; → anthropic; → principle.

A galaxy with prominent stellar → spiral arms and little star formation between stellar arms, such as M51.

→ strong; → arm; → spiral; → galaxy.

In a star cluster, a → close encounter that strongly changes a star's velocity.

→ strong; → encounter.

The force responsible for holding quarks and gluons together to form protons, neutrons and other particles. It is the strongest of the four fundamental forces. Same as → strong interaction.

→ strong; → force.

A → gravitational lensing phenomenon in which the image distortion is strong enough to be readily recognized, such as in the case of the → Einstein cross or when giant luminous arcs show up in → galaxy clusters (e.g. Abell 2218). Opposite to → weak gravitational lensing.

→ strong; → gravitational; → lensing.

The interaction between quarks that is transmitted by gluons. The characteristic range of the strong interaction is 10^-13 cm, and the time scale over which it operates is on the order of 10^-23 second. Also called → strong force.

→ strong; → interaction.

A situation where the mass concentration in the central regions of → galaxy clusters exceeds the → critical density required for lensing, resulting in multiple images of background objects.

→ strong; → lensing.

A metallic chemical element; symbol Sr. Atomic number 38; atomic weight 87.62; melting point 769°C; boiling point 1,384°C; specific gravity 2.6 at 20°C. Strontium is a soft, silver-yellow metal with three allotropic crystalline forms. It is found in nature only in the combined state, as in strontianite. It is used in fireworks, flares, and tracer bullets. The radioactive isotope Strontium-87, the daughter of Rubidium-87, has a half-life of 48.8 x 10⁹ years.

The name derives from Strontian "a town in Scotland." The mineral strontianite is found in mines in Strontian. The element was discovered by the Scottish chemist and physician Thomas Charles Hope in 1792 observing the brilliant red flame color of strontium. It was first isolated by the English chemist Humphry Davy in 1808.

The study of the processes that gave rise to the apparition of matter concentrations, such as → superclusters of galaxies, → galaxy clusters, and galaxies, in a homogeneous → expanding Universe. Cosmic structures are believed to result from → density fluctuations that existed in the → early Universe before radiation and matter decoupled (→ decoupling era or → recombination era). Initial → quantum fluctuations in the → inflaton field were expanded by → inflation. Inflation amplified them up to scales that correspond to those of galaxy clusters and beyond. Generally, a model of structure formation includes three main ingredients: 1) background cosmology, 2) model for fluctuation generation, and 3) types of → dark matter.
See also:
→ bottom-up structure formation, → hierarchical structure formation, → Silk damping, → top-down structure formation.

→ structure; → formation.

A measure of angle smaller than 1 arcsecond, usually until 0.1 arcsecond.

→ sub-; → arc second.

Imaging in excellent seeing conditions using an adequate detector to obtain stellar images whose profile lies in the sub-arcsecond range.

→ sub-arcsecond; → imaging.

Geology: The process by which one tectonic plate slides down and below another tectonic plate as the two converge. The subduction zone is the zone of convergence of two tectonic plates, one of which usually overrides the other.

From L. subductionem (nominative subductio), from subductus, p.p. of subducere "to draw away, withdraw, remove," from → sub- + ducere "to lead."

Zir-hâzeš, verbal noun of zir-hâzidan, from zir-→ sub- + hâzidan, hâxtan, from Mid.Pers. "to lead, guide, persuade;" Av. hak-, hacaiti "to attach oneself to, to join;" cf. Skt. sacate "accompanies, follows;" Gk. hepesthai "to follow,"; L. sequi "to follow;" PIE *sekw-.