(astronomy) An observational branch of astronomy, which deals with the study of X-ray emission from celestial objects.

The time it takes the Earth to pass once around the Sun, particularly a tropical, sidereal, or anomalistic year.

(nautical) Navigation by using the positions of the stars and other heavenly bodies / (science fiction) Navigation through space

A person who studies radio astronomy.

plural of radio astronomer

(obsolete) An astrologer.

The period in which the sun is between 12° and 18° below the horizon in the morning and evening.

plural of astronavigator

One who performs astronavigation; an astronaut or space pilot.

In an astronautic way.