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

The angle of the light coming out of a medium. For a medium with parallel sides (such as a glass slab) it is equal to the angle of incidence.

→ angle; → emergence.

The collision of two → black holes in a → binary black hole system once they come so close that they cannot escape each other's gravity. They will merge in an extremely violent event to become one more massive black hole. The merger would produce tremendous energy and send massive ripples, called → gravitational waves, through the → space-time fabric of the Universe. Such an event (called GW150914) was first detected by the → Laser Interferometer Gravitational-Wave Observatory (LIGO) on September 14, 2015. The initial black hole masses were 36 and 29 Msun which gave a final black hole mass of 62 Msun, with 3 Msun radiated in gravitational waves. The event happened at a distance of 1.3 billion → light-years from Earth (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). Black hole merger is preceded by → inspiral and followed by → ringdown.

→ black; → hole; → merger.

A merger between → gas-poor  → early-type galaxies.

→ dry; → merger.

1) Move out of or away from something and become visible.
2) To rise or come forth from or as if from water or other liquid (Dictionary.com).

→ ex-, + merge, → submerge.

1) The process of becoming visible after being concealed.
2) The escape of an insect or other invertebrate from an egg, cocoon, or pupal case.
3) The process of coming into existence or prominence (OxfordDictionaries.com).

→ emerge; → -ence.

1) Coming into being or notice.
2) Philo.: (of a property) arising as an effect of complex causes and not analyzable simply as the sum of their effects.
3) Ecology: Of or denoting a plant which is taller than the surrounding vegetation, especially a tall tree in a forest (OxfordDictionaries.com).

→ emerge; → -ent.

Optics: The → light ray leaving a → medium, in contrast to the → incident ray. If the medium has parallel sides, → angle of incidence and → angle of emergence

→ emergent; → ray.

To plunge into or place under a liquid; dip; sink (Dictionary.com).

→ in- + merge, → submerge.

The → merging of two spiral galaxies with roughly equal masses colliding at appropriate angles. The dynamical friction is so efficient that the galaxies merge after only a few perigalactic passages.

→ major; → merger.

1) (v.intr.) To become combined, united, swallowed up, or absorbed; lose identity by uniting or blending.
2) (v.tr.) To cause to combine or coalesce. To combine, blend, or unite gradually so as to blur the individuality or individual identity of.
Related terms: → fuse, → coalesce. See also → merger, → mergeburst, → merger process, → merger tree, → merging, → merging galaxy, → minor merger, → mixed merger, → wet merger.

From L. mergere "to dip, immerse," probably rhotacized from *mezgo, and cognate with Skt. majj- "to dive, to sink," majjati "dives under;" Lith. mazgoju "to wash."

Taškidan, taškândan, from Gilaki tašk "tie, knot;" Tabari tešk "knot" + -idan infinitive suffix.

A hypothetical → transient event undergone by a → star due to its violent → merging with another star in a → close binary star. The release of → orbital energy causes the → envelope of the star to heat up and → inflate, causing the star to brighten considerably. Mergebursts are predicted to rival or exceed the brightest classical → novae in luminosity, but to be much cooler and redder than classical novae, and to become slowly hotter and bluer as they age.

→ merge; → burst.

1) Any combination of two or more bodies into a single body. In particular, the formation of a galaxy from the collision of two or more separate galaxies.
2) An act or instance of merging.

From → merge + -er (as in waiver).

Tašké; tašk, nouns from taškidan, → merge.

The process of collision between galaxies which leads to a single galaxy.

→ merger; → process.

A method used in → numerical simulations for studying the growth and development of galaxies and → dark matter halos. Within the currently accepted ΛCDM cosmology, dark matter halos merge from small → clumps to ever larger structures. This merging history can be traced in simulations and stored in the form of merger trees. Merger trees are necessary because a galaxy may have more than one → progenitor at an early time.

→ merger; → tree.

The → merging in which one of the galaxies is significantly larger than the other (mass ratios above 10). The larger galaxy will often "swallow" the smaller satellite galaxy. The swallowed galaxy can trigger disk and nuclear star formation or activate a central core with shells that surround the predator.

→ minor; → merger.

A merger that takes place when a → gas-poor galaxy collides with a → gas-rich galaxy.

Past-participle of → mix; → merger.

1) To sink or plunge under water or beneath the surface of any enveloping medium.
2) To cover or overflow with water; immerse (Dictionary.com).

From L. submergere, from → sub- + mergere "to dip, immerse;" probably by rhotacism from PIE *mezg- "to dip, plunge;" cf. Skt. majj- "to sink in water;" Lith. mazgoju "to wash."

Marcidan, from Av. mraoc- "to float, submerge;" cf. Skt. mroc/mloc "to go down, set (of the Sun), to disappear, to hide;" Kurd., Laki, Nahâvandi, Bovir-Ahmadi mala- "swim," Kurd. melâna "ship, boat," melaq "wave" may be related to this Av. form.

A merger between → gas-rich galaxies. Wet mergers may lead to enhanced star formation, trigger → active galactic nuclei, and transform a → disk galaxy into an → elliptical galaxy. The larger the → redshift, the wetter mergers should be.

→ wet; → merger.