astro-, astr- +

(Greek: star, stars, star shaped; also pertaining to outer space)

astronomical twilight
The time between sunset or sunrise and the moment when the sun's center lies 18 degrees below the horizon.
astronomical unit, AU
1. The mean distance of the earth from the sun, which is 149,597,870 kilometers, or about 93 million miles.
2. A unit of length used by astronomers to measure distances in space.

One astronomical unit, or AU, is equal to the average distance between the earth and the sun, which is 92,955,806 miles or 149,597,870 kilometers.

astronomically
1. A reference to astronomy or the scientific study of stars, planets, and other objects in outer space.
2. Referring to anything which is large in size or quantity: "The cost of health care has risen astronomically."
astronomize
To study or to talk about astronomy.
astronomy
1. The scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena.

Astronomy literally means "law of the stars" or "culture of the stars"; depending on the translation, and it is derived from the Greek αστρονομία, astronomia, from the words άστρον, astron, "star" and νόμος, nomos, "laws" or "cultures".

2. The science that deals with the material universe beyond the earth's atmosphere.
3. The scientific study of the universe, especially of the motions, positions, sizes, composition, and behavior of astronomical objects.

These objects are studied and interpreted from the radiation they emit and from data gathered by interplanetary probes.

The sun, moon, and the stars would have disappeared long ago, had they happened to be within reach of predatory human hands.
—Havelock Ellis
astronomy unit
The average distance from earth to the sun; about 150 million kilometers.
astrophile
1. Someone who is fond of star lore or the acquired knowledge or wisdom about stars; such as, those from local traditions, handed down by word of mouth and usually in the form of stories or historical anecdotes.
2. A love or fondness of the stars.
astrophilic
A reference to someone who has a love or fondness for the stars.
astrophobia (s) (noun) (no plural)
An excessive fear of stars and how they may have adverse influences on one's life or destiny: Since she was a child, Susan suffered from astrophobia and refused to go out when the night was dark and cloudless believing that she would be predestined to doom.
astrophobic (adjective), more astrophobic, most astrophobic
A reference to an excessive or morbid dread of stars and how they may have negative influences on one’s life or future destiny: Tim thought a lot about his job after completing his university education and decided to avoid going out at night because of his astrophobic anxieties which might affect his career in an adverse and destructive way.
astrophotograph
Photography as used in astronomical investigations.
astrophotographer
Someone who specializes in a type of photography that entails making photographs of astronomical objects in the night sky; such as, planets, stars, and deep sky objects including star clusters and galaxies.
astrophotography
1. The art of photographing astronomical objects and events for astronomical studies>
2. The photography of stars and other celestial objects.
3. The use of photographs to record extraterrestrial objects in order to study their surface features, positions, motions, radiation, and spectra.
astrophotometer
1. A photometer (light meter) for measuring the brightness of stars.
2. The measurement of the intensity of light of celestial objects.
astrophotometrical
Relating to the measurement of the intensity of light of celestial objects.

Links to star words Other "star" units: aster-, sidero-, stell-.

Links to astronomical wordsYou may also see an extensive list of astronomy; astronomical terms at this Get Words site.