ADaptive Optics Near Infrared System (ADONIS)
Fr.: ADaptive Optics Near Infrared System (ADONIS)
An → adaptive optics instrument used on the → European Southern Observatory (ESO) 3.6-m telescope at La Silla. It was an upgraded version of COME-ON-PLUS, the → Very Large Telescope (VLT) adaptive optics prototype. It had 52 → actuators and performed corrections of the mirror 200 times per second. The reference → wavefront was sensed in the → visible. The observation was done in the → near-infrared (1-5 μm).
federated database system (FDBS)
râžmân-e pâygâh-e dâdehâ-ye hiyâvidé
Fr.: système de base de données fédéré
A composition of different databases which work in an integrated manner while preserving their autonomy.
Global Positioning System (GPS)
râžmân-e nehešdâd-e jahâni
Fr.: système de positionnement par satellites
A coordinate positioning tool, using a combination of satellites that can rapidly and accurately determine the → latitude, → longitude, and the → altitude of a point on or above the Earth's surface. The GPS is based on a constellation of 24 Earth-orbiting satellites at an altitude of about 26,000 km. The system is a direct application of the thories of → special relativity and → general relativity.
High Energy Stereoscopic System (H.E.S.S.)
râžmân-e estereyo-ye meh kâruž (H.E.S.S.)
Fr.: Système stéréoscopique de haute énergie (H.E.S.S.)
An array of → IACT telescopes for studying cosmic → gamma rays in the 100 GeV to 100 TeV energy range. The HESS observatory is located in Namibia, southern Africa, at an altitude of 1800 m, and the project is an international collaboration of more than 100 scientists from nine countries. In its Phase I, HESS used four telescopes each consisting of a light collector with a diameter of 13 m and a focal length of 15 m placed at the corners of a square 120 m apart. Each telescope is segmented into 380 round mirror facets of 60 cm diameter and uses a camera consisting of 960 closely packed → photomultiplier tubes. The first of the telescopes went into operation in Summer 2002. Phase II includes a fifth telescope, called Large Cherenkov Telescope (LCT), of 27 m diameter, located in the centre of the initial array. This upgrade lowers the triggering threshold of the HESS array to about 20 GeV, thus broadening the energy window in which gamma-ray astronomy can be done, opening up more opportunities in astrophysical research (see, e.g., Bernlöhr et al. 2003, Astroparticle Physics 20, 111).
H.E.S.S., short for High Energy Stereoscopic System, is also intended to pay homage to Victor F. Hess (1883-1964), an Austrian-American physicist who received the Nobel Prize in Physics in 1936 for his discovery of → cosmic rays.
International System of Units (SI)
râžmân-e jahâni-ye yekâhâ
Fr.: système international des unités
The metric system of units based on the → meter, → kilogram, → second, → ampere, → kelvin, and → candela. Also called MSKA system. Other SI units are → hertz, → radian, → newton, → joule, → watt, → coulomb, → volt, → ohm, → farad, → weber, and → tesla.
Fr.: conversion intersystème
A → radiationless relaxation process in which a molecule in some excited → electronic state converts to a state of different spin → multiplicity. Intersystem crossing is analogous to → internal conversion.
Fr.: raie semi-interdite
In spectroscopy, same as → semi-forbidden line.
number system conversion
hâgard-e râžmân-e adadi
Fr.: conversion de système de numération
The conversion of a → number system
with a given → base to another system with a
different base; such as the conversion of a → decimal number
(base 10) to a → binary number system
In order to convert a number into its representation in a different
number base, we have to express the number in terms of powers of the other base.
For example, to convert the decimal number 100 to base 3, we must figure out how to
express 100 as the sum of powers of 3. We proceed as follows:
operating system (OS)
Fr.: système d'exploitation
small solar system body
jesm-e kucak-e râžmân-e xoršidi
Fr.: petit corps du système solaire
A term introduced by the → International Astronomical Union (August 2006) to name the → solar system bodies other than → planets and → dwarf planets. Small solar system bodies include → asteroids, → comets, and → meteoroids.
solar system abundance
farâvâni-ye râžmân-e xoršidi
Fr.: abondance dans le système solaire
Same as → protosolar abundance.
Fr.: administrateur de système
A person in charge of the configuration and administration of a multi-user computer system inside a network.
Fr.: bruit de système
The noise in a radio telescope, composed of the receiver noise and the sky noise.
unbound young stellar system (UYSS)
râžmân-e setâre-yi-ye javân-e nâbandidé
Fr.: système stellaire jeune non lié
A class of gravitationally loose stellar conglomerate with a notable apparent shape making it different from typical → bound → star clusters. The UYSS class includes a large range of objects, which extend at various size scales and at various degrees of self-binding; from small (semi-)compact → unbound systems named → stellar associations, to huge extended superstructures of → massive stars that make up whole parts of Galactic → spiral arms, known as → stellar complexes (Gouliermis, D. A., 2018, PASP 130:072001; arXiv:1806.11541).