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The total number of protons and neutrons in an atom's nucleus. For example, oxygen-16 has a mass number of sixteen, because it has eight protons and eight neutrons.
Industry:Astronomy
The masses of atoms and molecules are generally given in atomic mass units. These units are based on a scale in which the mass of carbon 12 is taken to be 12. Atomic masses were originally given as atomic weights on a scale where the mass of the hydrogen atom was unity, later they were based on oxygen or oxygen 16; these scales have all been replaced by the carbon 12 scale.
Industry:Astronomy
The number of protons in an atom's nucleus. This determines the type of element.
Industry:Astronomy
the light produced by excited atoms and ions in the upper atmosphere of a planet
Industry:Astronomy
1) Angular distance from the north point eastward to the intersection of the celestial horizon with the vertical circle passing through the object and the zenith.
2) Directional bearing around the horizon, measured in degrees from north (0 degree.)
Industry:Astronomy
A measure of the minor axis of an elliptic orbital of an electron according to the Bohr-Sommerfeld theory.
Industry:Astronomy
A nuclear reaction (3 4He → 12C + γ + 7 MeV) by which helium is transformed into carbon. The process is dominant in red giants. At a temperature of about 2 × 108 K and a density of 105 g cm-3, after core hydrogen is exhausted, three α-particles can fuse to form an excited nucleus of carbon 12, which occasionally decays into a stable carbon 12 nucleus. The overall process can be looked upon as an equilibrium between three helium nuclei and the excited 12C*, with occasional irreversible leakage out of the equilibrium into the ground state of carbon 12. Further capture of α-particles by carbon 12 nuclei produces oxygen 16 and neon 20. (also called the triple-α process.)
Industry:Astronomy
1) A measure of the intrinsic brightness of a star or galaxy. Absolute magnitude is defined as the apparent magnitude the star or galaxy would have if it were 32.6 light-years (10 parsecs) from Earth. The lower an object's absolute magnitude, the greater its intrinsic brightness. For example, the Sun has an absolute magnitude of +4.83, while Sirius, whose intrinsic brightness is greater, has an absolute magnitude of +1.43. A star that is one absolute magnitude brighter than another (e.g., +4 versus +5) is 2.5 times intrinsically brighter; a star that is 5 absolute magnitudes brighter is 100 times intrinsically brighter; and a star that is 10 absolute magnitudes brighter is 10000 times intrinsically brighter.
2) The absolute magnitude (g) of a solar-system body such as an asteroid is defined as the brightness at zero phase angle when the object is 1 AU from the Sun and 1 AU from the observer.
Industry:Astronomy
