Many words have been dedicated to the English language, and some to astronomy itself! We all know this as a fact, but some astronomy-related terms are lesser known than others, and this article is dedicated to them. In the first list, all words below are courtesy the Grandiloquent Dictionary. Definitions provided by them; copyright Grandiloquent Dictionary.
achluophobia -( ) A fear of darkness or of the night
astrophobia -( ) The fear of stars
barophobia - ( ) Fear of gravity
heliolater - ( ) A sun worshipper
heliophobia - ( ) The fear of the Sun
heliotropism - ( ) The tendency of plants to turn towards the sun
hemeralopia - ( ) Only being able to see at night
hemeraphonia - ( ) Able to speak only at night
lygophobia - ( )A fear of darkness or of the night
myctophobia - ( ) A fear of darkness or of the night
nychthemeron - ( ) A period of 24-hours
phengophobia - ( ) The fear of the Sun or of sunlight
raith - ( ) A quarter of a year
scintillation - ( ) The twinkling of stars or small bursts of light
selenocentric - ( ) One whose life revolves around the moon
Below, more astronomical-related obscure terms are listed, although not necessarily from the Grandiloquent Dictionary.These are words from Dictionary.com and SeaSky Astronomical Dictionary.
Syzygy An alignment of three celestial objects, as the sun, the earth, and either the moon or a planet
Azimuth the arc of the horizon measured clockwise from the south point, in astronomy, or from the north point, in navigation, to the point where a vertical circle through a given heavenly body intersects the horizon.
Ephemeris a table showing the positions of a heavenly body on a number of dates in a regular sequence.
Protoplanet the collection of matter, in the process of condensation, from which a planet is formed.
Zenith the point on the celestial sphere vertically above a given position or observer.
Node either of the two points at which the orbit of a heavenly body intersects a given plane, especially the plane of the ecliptic or of the celestial equator.
Facula an irregular, unusually bright patch on the sun's surface.
achrondite A stone meteorite that contains no chondrules.
Apastron the point at which the stars of a binary system are farthest apart (periastron).
Catena A series or chain of craters.
Ejecta Material from beneath the surface of a body such as a moon or planet that is ejected by an impact such as a meteor and distributed around the surface. Ejecta usually appear as a lighter color than the surrounding surface.
Granulation one of the small, short-lived features of the sun's surface that in the aggregate give it a mottled appearance when viewed with a telescope.
Hypergalaxy A system consisting of a spiral galaxy surrounded by several dwarf white galaxies, often ellipticals. Our galaxy and the Andromeda galaxy are examples of hypergalaxies.
Libration An effect caused by the apparent wobble of the Moon as it orbits the Earth. The Moon always keeps the same side toward the Earth, but due to libration, 59% of the Moon's surface can be seen over a period of time.
Nadir the point on the celestial sphere directly beneath a given position or observer and diametrically opposite the zenith.
Obliquity The angle between a body's equatorial plane and orbital plane.
Planemo A large planet or planetary body that does not orbit a star. Planemos instead wander cold and alone through the cosmos. It is believed that most planemos once orbited their mother star but were ejected from the star system by gravitational interaction with another massive object.