Fr.: protoétoile de masse intermédiare
A protostar that evolves into an → intermediate-mass star.
Fr.: proto-étoile orpheline
A → protostellar object which has been dynamically ejected from a newborn → multiple star system, either into a tenuously bound orbit or into an escape, thus depriving it from gaining much additional mass. Recent observations have shown that → Class I protostellar sources have a population of distant companions at separations ~ 1000 to 5000 → astronomical unit (AU)s. Moreover, the companion fraction diminishes as the sources evolve. According to N-body simulations of unstable → triple systems embedded in dense cloud cores, many companions are ejected into unbound orbits and quickly escape, but others are ejected with insufficient momentum to climb out of the potential well of the cloud core and associated binary. These loosely bound companions reach distances of many thousands of AU before falling back and eventually being ejected into escapes as the cloud cores gradually disappear (B. Reipurth et al. 2010, arXiv:1010.3307).
From Gk. proto-, combining form of protos "first," superlative of pro "before," cognate with O.S. pruvu "first;" Rus. pervyy "first;" Av. pauruua-, as below.
Purvâ-, from O.Pers. paruviya- "former, initial," Av. pourva-, pouruuiia-, pauruua-, paoiriia- "first, initial, former;" cf. Skt. purva- "first, former, being before;" Tokharian B parwe "first;" PIE base *prwos "first."
The hypothetical but strongly evidenced common ancestor of the Indo-European languages. PIE words are reconstructed from extant Indo-European languages. There is no clear agreement on exactly where or when the speakers of PIE lived. It is believed that most of the subgroups diverged and spread out over much of Europe, Iran, and northern Indian subcontinent during the fourth and third millennia BC. See also → proto-language.
The hypothetical and typically extinct language which is believed to be the ancestor of a group of languages of the same family. Historical linguistics uses comparative study of the languages of a family to reconstruct the ancestral language even though in most cases it was never recorded. Some examples are → Proto-Indo-European, Proto-Germanic, Proto-Romance, Proto-Sino-Tibetan, etc.
A very huge mass of gas which will give rise to a cluster of galaxies.
Computers: A set of rules and methods used for communication and transmission of data between different computer systems. Protocols may be implemented by hardware, software, or a combination of the two. Simple protocols define the behavior of a hardware connection and help with error detection of the bit stream. High level protocols deal with the data formatting, including the syntax of messages, the terminal to computer dialogue, character sets, sequencing of messages etc.
M.E. prothogall "draft of a document," from M.Fr. prothocole, from M.L. protocollum "draft," literally "the first sheet of a volume" (on which contents were written), from Gk. protokollon "first leaf glued to the rolls of papyrus describing its contents," from → proto- "first" + kolla "glue."
Purvâband from purvâ-, → proto-, + band "joint; joined," past stem of bastan "to bind; to shut; to form seed buds; to clot," from 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.
A huge mass of gas that by contraction and condensation becomes a galaxy of stars. A galaxy during the early phase, before it has developed its present shape and stellar/gas content.
Fr.: disque proto-lunaire
A dense disk of liquid and vapor supposed to have formed around the Earth below the Roche limit after the proto-Earth was impacted by a Mars-sized object. The Moon was accreted from the Earth's mantle material froming the disk. See also → Theia (S. Charnoz and C. Michaut, 2015, arxiv.1507.05658).
Fr.: proto-étoile à neutrons
A compact, hot, and → neutrino-rich object that results from a → supernova explosion and is a transition between an → iron core and a → neutron star or → black hole. The life span of a protoneutron star is less than one minute.
Fr.: disque protoplanétaire
A → circumstellar disk of gas and dust surrounding a → pre-main sequence star from which planetary systems form. Protoplanetary disks are remnants of → accretion disks which bring forth stars. Typically, their sizes are ~100-500 AU, masses ~10-2 solar masses, lifetimes ~106-107 years, and accretion rates ~10-7-10-8 solar masses per year. According to the standard theory of planet formation, called core accretion, planets come into being by the growth of → dust grains which stick together and produce ever larger bodies, known as → planetesimals. The agglomeration of these planetesimals of 100 to 1000 km in size into rocky Earth-mass planets is the main outcome of this theory. Beyond the → snow line in the disk, if the masses of these cores of rock and ice grow higher than 10 times that of Earth in less than a few million years, gas can rapidly accrete and give rise to giant gaseous planets similar to → Jupiter. If core building goes on too slowly, the disk gas dissipates before the formation of → giant planets can start. Finally the left-over planetesimals that could not agglomerate into rocky planets or core of giant planets remain as a → debris disk around the central object that has become a → main sequence star. An alternative to core accretion theory is formation of planets in a massive protoplanetary disk by → gravitational instabilities. The validity of these two theories is presently debated. See also → protoplanet.
The fluid substance within the living cell that consists of two major divisions, the cytoplasm and the nucleoplasm (cell nucleus). It is composed mainly of nucleic acids, proteins, lipids, carbohydrates, and inorganic salts.
Fr.: abondance protosolaire
A stage in the process of → star formation, after the → gravitational collapse of the dense → pre-stellar core and before the initiation of → nuclear fusion in the central object which will eventually become a star. Protostars are classified into four groups: → Class 0, → Class I, → Class II, and → Class III.
Of or pertaining to → protostars.
Fr.: effondrement protostellaire
Fr.: disque protostellaire
Fr.: jet protostellaire
A high-velocity and highly → collimated jet associated with the earliest phase of → star formation that propagating along the polar axis of the → protostar-→ accretion disk system. Protostellar jets are usually detected in the [S II], [O I], and Hα lines and are therefore referred to as optical jets. They may have more than a parsec in length. Their formation is related to the → magnetohydrodynamics (MHD) of accretion disks. These jets are detected in protostellar sources over a wide range of masses, from the very early stages of formation (sources associated with infalling envelopes whose mass exceeds that of the growing star) all the way to the → classical T Tauri stars, whose envelopes have already dispersed. This phenomenon is thought to play a key role in regulating the star formation process by removing the excess → angular momentum of disk material and enabling matter to flow toward the center. Protostellar winds also provide an important → feedback mechanism between the forming star and the surrounding medium, to which they return mass and energy. Protostellar jets are at the origin of → bipolar outflows. The et sweeps up ambient → molecular cloud material into two thin shells, which manifest themselves as the observed bipolar lobes of → carbon monoxide (CO) emission. Once the molecular cloud material has been swept away (on a timescale of 105 years), the bipolar outflow disappears, leaving the protostellar jet to erratically fire away for a further 106-107 years.