An Etymological Dictionary of Astronomy and Astrophysics
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→ Turbulence in which spatial derivatives of all mean turbulent quantities are negligible.

→ homogeneous, → turbulence.

A model Universe which is homogeneous and → isotropic on large scales. It is modeled by a → Robertson-Walker cosmology. A homogeneous Universe is filled with a constant density and negligible pressure. Any small spatial region is characteristic for the whole Universe.

→ homogeneous; → Universe.

The condition or an instance of not being homogeneous.

→ in- "not" + → homogeneity.

Lack of homogeneity; something that is not → homogeneous.

→ in- "not" + → homogeneous.

Postulate that the magnitude of the lepton number density is comparable to or larger than the thermal radiation photon number density, so relaxation to equilibrium produces a degenerate sea of neutrinos. Degenerate neutrinos would suppress the number of neutrons relative to protons in the very early Universe; degenerate antineutrinos would suppress the number of protons relative to neutrons. Either case would affect BBNS (Peebles, P. et al., 2009, Finding the Big Bang, Cambridge: UK, Cambridge Univ. Press).

→ lepton; → degeneracy.

Determining the three various parameters of a microlensing event (the lens-source relative parallax and proper motion, and the mass of the lens) from only one physical parameter (the event time scale). Currently the microlensing degeneracy affects the vast majority of events and makes any individual event impossible to interpret with certainty.

→ microlensing; → degeneracy.

A period of → geologic time within the Cenozoic era, between 23 and 2.6 million years ago, which comprises the Miocene and Pliocene epochs.

From L. neo-, → new, + -gene, → gene.

The state of degeneracy created when the density of matter is so high that neutrons cannot be packed any more closely together. This condition occurs in the core of stars above 1.44 solar masses (→ Chandrasekhar limit) where under the gravitational collapse electrons and protons are forced to combine into neutrons. Therefore, in a → neutron star all the lowest neutron energy levels are filled and the neutrons are forced into higher and higher energy levels, since according to Pauli Exclusion Principle no two neutrons (fermions) can occupy identical states. This creates an effective pressure which prevents further gravitational collapse. However, for masses greater than 3 solar masses, even neutron degeneracy cannot prevent further collapse and it continues toward the black hole state.

→ neutron; → degeneracy.

A catalogue of 7,840 non-stellar objects compiled by J. L. E. Dreyer and published in 1888. A further 1,529 objects were listed in a supplement that appeared seven years later, called the → Index Catalogue (IC). The Second Index Catalogue of 1908 extended the supplementary list to 5,386 objects.

→ new; → general; → catalog

Not homogeneous. → nonhomogeneous linear differential equation.

→ non-; → homogeneous.

A → linear differential equation if Q(x)≠ 0 on interval I.

→ nonhomogeneous; → linear; → differential; → equation.

A period of → geologic time lasting about 42 million years, roughly from 65 to 23 million years ago. The Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals in the wake of the → Cretaceous-Paleogene extinction event that ended the preceding → Cretaceous period. Birds also evolved considerably during this period, changing into roughly modern forms.

Literally "ancient birth," from → paleo- + -gene, → gene.

Same as → PG 1159 star.

→ post-; → degenerate; → star.

1) To produce anew; bring into existence again; to bring new and more vigorous.
2) Biology: To renew or restore (a lost, removed, or injured part).
3) Physics: To restore (a substance) to a favorable state or physical condition.
4) Electronics: To magnify the amplification of, by relaying part of the output circuit power into the input circuit (Dictionary.com).

→ re-; → generate.

1) Act of regenerating; state of being regenerated.
2) Electronics: A feedback process in which energy from the output of an amplifier is fed back to the grid circuit to reinforce the input.
3) Biology: The restoration or new growth by an organism of organs, tissues, etc., that have been lost, removed, or injured (Dictionary.com).

→ re-; → generation.

1) Of, relating to, or characterized by regeneration.
2) Tending to regenerate.

→ re-; → generative.

A branch of medicine that replaces or regenerates injured or diseased human cells, tissue, or organs, to restore or establish normal function.

→ regenerative; → medicine.

A star whose formation is induced by an older star itself formed previously in the same region. See also → stimulated star formation, → sequential star formation, → triggered star formation.

→ second; → generation; → star.

The head or chief administrative officer of a secretariat.

→ secretary; → general.

The situation in which spectroscopic features in a certain optical region are not sensitive enough to distinguish adjacent → luminosity classes, for instance → dwarf stars from → giant stars.

→ spectroscopic; → degeneracy.