An Etymological Dictionary of Astronomy and Astrophysics
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An international collaboration using a → very-long-baseline interferometry (VLBI) array comprising millimeter- and → submillimeter- wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, the EHT → angular resolution (λ/D) is ~25 μas (→ micro- → arcseconds), which is sufficient to resolve nearby → supermassive black hole candidates on spatial and temporal scales that correspond to their → event horizons. EHT observations toward the elliptical → galaxy M87 succeeded in obtaining the first ever image of its supermassive black hole (EHT Collaboration, 2019, ApJL 875, L1-L6). The telescopes contributing to this result were ALMA, APEX, the IRAM 30-m telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope. Petabytes of raw data from the telescopes were combined by highly specialized supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory. The construction of the EHT and the M87 black hole observation result from decades of observational, technical, and theoretical work in close collaboration by researchers from around the world. Thirteen partner institutions worked together to create the EHT, using both pre-existing infrastructure and support from a variety of agencies. Key funding was provided by the US National Science Foundation (NSF), the EU's European Research Council (ERC), and funding agencies in East Asia.

→ event; → horizon; → telescope.

The act or fact of evoking.

Verbal noun of → evoke.

Any process of formation or growth; development; a process of gradual, progressive change; a product of such development; something evolved.
Astro.: A continuous and progressive change according to certain laws and by means of acting physical forces.
Biology: A process of development in which a living organism, through major environmental changes, becomes more and more complex by the differentiation of its parts.

Verbal noun of → evolve.

Of, pertaining to, or in accordance with a theory of evolution.

Adjective of → evolution.

The stellar mass based on → effective temperature and → luminosity, as derived from → evolutionary tracks.

→ evolutionary; → mass.

A model, based on theoretical calculations, which predicts the behavior of an astronomical entity (stars, galaxies, Universe) over time.

→ evolutionary; → model.

A particular step or phase in the evolution of an astronomical object.

→ evolutionary; → stage.

The characteristic time it takes an evolving astronomical object to pass from a step to another.

→ evolutionary; → time scale.

In a theoretical → Hertzsprung-Russell diagram, the path taken by an evolving star.

→ evolutionary; → track.

A → differential equation composed of → continuous  → differentiable functions for which certain conditions are fulfilled. The equation M(x,y)dx + N(x,y)dy = 0 is called exact if M(x,y) and N(x,y) are continuous differentiable functions for which the following relationship is fulfilled: ∂M/∂y = ∂N/∂x, and ∂M/∂y and ∂N/∂x are continuous in some region.

→ exact; → differential; → equation.

1) The act of examining; inspection; inquiry; investigation.
2) The state of being examined.
3) The act or process of testing pupils, candidates, etc., as by questions (Dictionary.com).

Noun from → examine.

1) The act of excepting or the fact of being excepted.
2) Something excepted. 

Verbal noun of → except.

Forming an exception; not ordinary.

→ exception; → -al.

The act of removal; an excising. The surgical removal of a foreign body or of tissue.

Verbal noun of → excise.

1) The addition of → energy to an → atomic or → molecular system, → transferring it from its → ground state to an → excited state.
2) A property of an → emission nebula usually expressed by the ratio [O III] 5007Å/Hβ.

Verbal noun of → excite; → -tion.

Amount of energy (usually measured in → electron-volts) required to bring an electron from its → ground state to a given → excited state.

→ excitation; → energy.

In quantum mechanics, the energy that is necessary to change a system from a → ground state to a given → excited state; also called excitation energy.

→ excitation; → potential.

Of a gas or plasma, the temperature deduced from the → populations of atomic → excited states, as expressed by the Boltzmann formula: N_u/N_l = (g_u/g_l) exp (-ΔE/kT_ex), where N_u and N_l are the upper level and lower level populations respectively, g_u and g_l the statistical weights, ΔE = hν the energy difference between the states, k is → Boltzmann's constant, and h→ Planck's constant. The higher the energy of the occupied states, the higher the excitation temperature.

→ excitation; → temperature.

An act or instance of excluding; the state of being excluded.

Verbal noun of → exclude.

In → quantum mechanics, the principle according to which no → two → fermions of the same kind may simultaneously → occupy the same → quantum state. Also known as → Pauli exclusion principle.

→ exclusion; → principle.