An Etymological Dictionary of Astronomy and Astrophysics
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Of or relating to → interferometry.

→ interferometer; → -ic.

A system of several telescopes coupled together in a particular configuration to carry out → interferometry.

→ interferometric; → array.

An observational technique based on principles of → interferometry.

→ interferometric; → technique.

1) A mathematical → expression consisting of an → array of → components which are needed for calculating → infinitesimally small → distances between two → points in some geometrical → space. More simply put, the → function used to define a distance between two points in a → metric space. Also called → distance function.
2) In → general relativity the metric describes the → space-time geometry and gives the interval between two neighboring → events.
3) Pertaining to the meter or to the → metric system.

From → meter + → -ic.

Any of the suffixes adopted by the International System of Units (→ SI units).
For numbers larger than 1: → deca- (10¹), → hecto- (10²), → kilo- (10³), → mega- (10⁶), → giga- (10⁹), → tera- (10¹²), → peta- (10¹⁵), → exa- (10¹⁸), → zetta- (10²¹), and → yotta- (10²⁴) .
For numbers smaller than 1: → deci- (10^-1), → centi- (10^-2), → milli- (10^-3), → micro- (10^-6), → nano- (10^-9), → pico- (10^-12), → femto- (10^-15), → atto- (10^-18), → zepto- (10^-21), and → yocto- (10^-24).

→ metric; → prefix.

An set of points such that the distance between every pair of points is defined by a → distance function with the following properties: 1) the distance from the first point to the second equals zero if and only if the points are the same, 2) the distance from the first point to the second equals the distance from the second to the first, and 3) the sum of the distance from the first point to the second and the distance from the second point to a third exceeds or equals the distance from the first to the third.
In mathematical language, the properties, for a nonempty set X, can be expressed as:
1) d(x,y)≥ 0 and d(x,y) = 0 if and only if x = y.
2) d(x, y) = d(y,x) for all x, y ∈ X.
3) d(x,z)≤ d(x,y) + d(y,z) for all x, y, and z ∈ X. Also called → triangle inequality.

→ metric; → space.

A standard system of measurement using decimal units, in which the units of length, time, and mass are meter, second, and kilogram respectively.

→ metric; → system.

The abstract tensor operation which is computed in a particular → reference frame using the → metric components. The metric tensor defines magnitude and direction of vectors about a point.

→ metric; → tensor.

A physical → measurement unit in the → metric system.

→ metric; → unit.

The → metric that belongs to a four-dimensional → flat manifold and is given by ds² = - dt² + dx² + dy² + dz². Three coordinates represent → space and the fourth coordinate is devoted to → time. The Minkowski metric underlies the → geometry of → special relativity. Compare → Robertson-Walker metric.

In honor of Hermann Minkowski (1864-1909), Russian-born German mathematician, who introduced the concept of the four-dimensional nature of space-time; → metric.

Any of a set of equations that defines the coordinates of the dependent variables of a curve or surface in terms of one or more independent variables or parameters.

→ parametric; → equation.

Pertaining to or related to → photometry.

→ photometer + → -ic.

The range of → wavelengths allowed by a → filter used in a → photometric system.

→ photometric + → band.

A binary star whose binarity is detectable from its variability and light-curve that has certain specific characteristics.

→ photometric + → binary.

A calibration which converts the measured relative magnitudes into an absolute photometry.

→ photometric + → calibration.

A method of deriving the distance of a star using its → apparent magnitude and the → absolute magnitude inferred from its → spectral type.

This is a misnomer, because the method has nothing to do with parallax; → photometric; → parallax.

A system of → magnitudes, each of them characterized by a set of well-defined → passbands (or → filters) with known → response curves. The system is defined by the values given for the → standard stars. See also:
→ AB magnitude system, → five-color system, → Stromgren system, → JHK system, → UBV system, → uvby system.

→ photometric; → system.

Of or relating to → polarimetry.

→ polarimetry; → -ic.

A dating method that uses measurements of certain radioactive isotopes to calculate the ages in years (absolute age) of rocks and minerals.

→ radiometer; → dating.

A positive-definite inner product, (.,.)_x, on T_x(M), the tangent space to a manifold M at x, for each x  ∈ M, which varies continually with x (Douglas N. Clark, Dictionary of Analysis, Calculus, and Differential Equations).

→ Riemannian; → metric.