An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The velocity and direction of motion of a star or celestial object with respect to the Local Standard of Rest. Same as → peculiar velocity.

→ space; → motion.

A spacecraft carrying instruments intended for use in exploration of the physical properties of outer space or celestial bodies other than Earth.

→ space; → probe.

A reusable space vehicle designed to travel between the Earth and an orbiting space station for specific missions (carrying a crew and a cargo deploying and retrieving satellites) and then to return.

→ space; M.E. shotil (n.); O.E. scytel "a dart, arrow;" cf. O.N. skutill "harpoon;" akin to shut, shoot.

Nâvak "small ship; ship like," from nâv "ship" (O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" cf. Skt. nau-, nava- "ship, boat;" Gk. naus "ship;" L. nauticus "pertaining to ships or sailors") + -ak diminutive/similarity suffix. Nâvak also means "a small arrow, an arrow flying swift," which may have a different origin.

A program aimed at monitoring the near-Earth environment for recognizing and preventing space hazards by means of radar and optical observations from either space or the ground. The objective of the → European Space Agency initiative is to support the European independent utilization of, and access to, space for research or services, through the provision of timely and quality data, information, services and knowledge regarding the space environment, the threats and the sustainable exploitation of the outer space surrounding our planet Earth. The SSA Program was authorized at the November 2008 Ministerial Council and formally launched on 1 January 2009. The mandate was extended at the 2012 and 2016 Ministerial Councils, and the program is funded through to 2020. The program comprises three segments: 1) Space Surveillance and Tracking (SST), which is the monitoring and tracking of every object orbiting the Earth, such as satellites, space stations and debris. The objective is the prediction and warning of collisions and re-entry events. 2) → Space Weather (SWE), which aims at detection and forecasting of space weather and its effects through monitoring of the Sun, solar wind, magnetosphere, radiation belts, ionosphere and disturbances in the geomagnetic field. 3) → Near-Earth Objects (NEOs), which provides warning services against potential asteroid impact risks, including discovery, identification, orbit prediction and civil alert capabilities.

→ space; → situation; → -al; → awareness.

A large satellite equipped to support a human crew and designed to remain in orbit around Earth for an extended period and be used for a variety of purposes (conducting research, repairing satellites, performing other space-related activities).

→ space; → station.

The systematic application of science, technology, and engineering to the exploration and utilization of outer space.

→ space; → technology.

A telescope which is placed in an orbit around the → Earth and operates through commands from sent from the control center on Earth, such as → Hubble space telescope, → Herschel satellite, → Infrared Astronomical Satellite (IRAS), → Infrared Space Observatory (ISO), → International Ultraviolet Explorer (IUE), → Planck Satellaite , → Spitzer Space Telescope.

→ space; → telescope.

The velocity of a star relative to the Sun.

→ space; → velocity.

The varying conditions in space and specifically in the near-Earth environment. Space weather is chiefly solar driven, resulting from solar activities such as → solar flares, → solar wind, and → coronal mass ejections that affect → magnetosphere, → ionosphere, and → thermosphere. Non-solar sources such as Galactic → cosmic rays, → meteoroids, and → space debris can all be considered as altering space weather conditions at the Earth. Space weather may affect the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health. The research in this field aims at monitoring and diagnosis of space weather conditions and constructing reliable numerical prediction models. See also → Space Situational Awareness.

→ space; → weather; → meteorology.

The slight erosion of Solar System bodies (planets, moons, asteroids) caused by the → solar wind, → cosmic rays, and → micrometeorite bombardments. Space weathering affects the physical and optical properties of the surfaces of these bodies. Understanding this process is therefore important for the interpretation of remotely obtained spectral data, such as space probe photographs of outer Solar System moons.

→ space; → weathering.

A physical entity resulting from the union of space and time concepts. In its most simple version space-time is the four-dimensional continuum, having three spatial coordinates and one temporal coordinate, in which any → event or physical object is located. In → special relativity it is Minkowski's flat space-time. In → general relativity, it is described by a curved entity characterized by a → metric. Free-fall motion describes the → geodesic of this curved space-time. It may have additional dimensions in the context of speculative theories, such as → string theory.

→ space; → time.

→ curvature of space-time.

→ space; → time; → curvature.

A simple way of representing the → space-time continuum, usually including time and only one spatial dimension. The curve of a particle's equation of motion on a space-time diagram is called a → world line. Same as → Minkowski diagram.

→ space; → time; → diagram.

1) In Einstein's → theory of relativity, ds² = c²dt² - dx² - dy² - dz².
2) In → Newtonian mechanics, time interval: dt; space interval at fixed time: dl² = dx² + dy² + dz².

→ space-time; → interval.

A vehicle designed to travel or operate, with or without a → crew, in a controlled → flight pattern in space beyond the Earth's atmosphere or in → orbit around the Earth. Also called spaceship.

→ space; → craft.

Of, pertaining to, or describing an → event being outside the → light cone.

→ space; → like.

The → space-time interval between two → events if it is imaginary, i.e. ds²< 0.

→ spacelike; → interval.

→ space-time.

→ space; → time.

An infrared telescope launched by NASA on 25 August 2003, the last in the series of Great Observatories. It was placed into a heliocentric orbit with a period of revolution that causes it to drift away from Earth at a rate of 0.1 → astronomical unit per year. Spitzer has a 85-cm primary mirror, made of beryllium and is equipped with three cryogenically-cooled science instruments: 1) IRAC (Infrared Array Camera), which operates simultaneously on four wavelengths (3.6, 4.5, 5.8, and 8 µm); 2) IRS (Infrared Spectrograph), with four sub-modules which operate at the wavelengths 5.3-14 µm (low resolution), 10-19.5 µm (high resolution), 14-40 µm (low resolution), and 19-37 µm (high resolution); and 3) MIPS (Multiband Imaging Photometer for Spitzer), three detector arrays in the → far infrared at 24, 70, and 160 µm. So far Spitzer has obtained precious data on all sorts of astronomical objects, thus contributing to all fields of astrophysics. It has also performed two sky surveys: GLIMPS, which covers 300° of the inner Milky Way galaxy, consisting of approximately 444,000 images taken at 4 separate wavelengths with the IRAC, and MIPSGAL a similar survey covering 278° of the Galactic disk at longer wavelengths.The planned nominal mission period was to be 2.5 years with a pre-launch expectation that the mission could extend to five or slightly more years until the onboard liquid helium supply was exhausted. This occurred on 15 May 2009. Without liquid helium to cool the telescope, most instruments are no longer usable. However, the two shortest wavelength modules of the IRAC camera are still operable and will continue to be used in the Spitzer Warm Mission.

Named in honor of Lyman Spitzer (1914-1997), an American theoretical physicist and astronomer best known for his research in star formation and plasma physics, who first suggested (1940s) placing telescopes in orbit to escape interference from the Earth's atmosphere; → space; → telescope.

A set X together with a collection of open subsets T that satisfies the three following conditions: 1) The empty set Ø and X are in T. 2) The intersection of a finite number of sets in T is also in T. 3) The union of an arbitrary number of sets in T is also in T.

→ topological; → space.