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

The → zero point of the → Kelvin scale of → temperature; the theoretical point at which all molecular activity ceases, -273.16 °C.

→ absolute; → zero.

Not equal to zero.

→ non-; → zero.

A → polynomial that at least has one non-zero → coefficient. See also → zero polynomial.

→ non-zero; → polynomial.

1) The cardinal number of a class that has no members.
2) The only integer that is neither negative nor positive.
3) The → identity element for addition.

From Fr. zéro, from It. zero, from M.L. zephirum, from Ar. sifr (صفر) "cipher," translation of Skt. śūnya "empty place, void, naught." The rules governing the use of zero appeared for the first time in the Indian mathematician Brahmagupta's book Brahmasputha Siddhanta "The Opening of the Universe," written in 628.

A star that has arrived on the → horizontal branch after leaving the → red giant branch. It begins → helium burning in its core.

→ zero; → age; → horizontal; → branch; → star.

The position on the → Hertzsprung-Russell diagram for newborn stars which have just started → hydrogen burning in their cores. The ZAMS forms the lower luminosity boundary of of the → main sequence strip. See also → terminal age main sequence (TAMS).

→ zero; → age; → main sequence.

Same as → null matrix.

→ zero; → matrix.

same as → null method.

→ zero; → method.

1) General: A starting point for making a measurement.
2) A basic parameter on which a → photometric system relies and must be determined each night. The zero points of → magnitudes and color indices (→ color index) depend on atmospheric transparency that varies from night to night.

→ zero; → point.

The lowest possible energy that a → quantum mechanical system may possess. It is the energy of the → ground state of the system. The term "zero point" refers to the observed fact that → vacuum fluctuations persist at → absolute zero temperature. Same as → vacuum energy.

→ zero; → point; → energy.

A → polynomial whose → coefficients are all zero. See also → non-zero polynomial.

→ zero; → polynomial.

The removal of non-significant zeroes from a number. For example, replacing 531.2300 by 531.23.

→ zero; → suppression.

In the → restricted three-body problem, a surface which limits the region of space in which a small body can move. In the expression for the → Jacobi integral, the left side value is always positive or nul; hence the particle motion is confined to the region where U ≤ C_J. The surface that limits this region, defined by U = C_J, is called the zero-velocity surface.

→ zero; → velocity; → surface.

Two objects that are in → thermal equilibrium with a third object will be in thermal equilibrium with each other.

→ zero; → law; → thermodynamics.