There are so many astronomical objects out there behaving in mysterious ways that astronomers are still trying to figure out. A brand new set of words and language has to be invented every time something is discovered and that is part of what makes the study of space so interesting. There’s so much out there that is waiting to be found.
The use of mythological and ancient names to name all the objects that are in space has also always given astronomy an air of mystery and wonder that attracts all kinds of people and incentivizes them to look at the sky every night.
There are so many space-related words and terms that it is hard to keep up.
This is why below, we have compiled a list of space words that start with A so you can learn more about the study of the universe. These are words that are related to astronomy and space, if what you are looking for is specifically for name ideas or the names of objects, check out our lists of star names, planets, or constellations. You will also find those sorted by letter.
| Word | Meaning |
|---|---|
| Absolute Magnitude | Measure of a celestial object’s intrinsic brightness. |
| Absolute Zero | Lowest possible temperature, 0 Kelvin or -273.15 degrees Celsius. |
| Accretion | Process of matter accumulating onto a celestial object. |
| Accretion Disk | Rotating disk of gas and dust around a central object. |
| Active Galactic Nucleus | Central region of a galaxy with a high-energy output. |
| Active Region | Area on the Sun’s surface with increased magnetic activity. |
| Adaptive Optics | Technology to correct distortions caused by Earth’s atmosphere in telescopes. |
| Airlock | Sealed chamber used for entering and exiting a spacecraft in space. |
| Albedo | Reflectivity of a surface, often of a planet or moon. |
| Aldebaran | Brightest star in the Taurus constellation. |
| Almagest | Ancient Greek astronomical treatise by Ptolemy. |
| Alpha Centauri | Closest star system to the Solar System. |
| Altazimuth Mount | Telescope mount with vertical and horizontal rotation axes. |
| Altitude | Height above a reference point, usually Earth’s surface. |
| Analemma | Figure-eight shape traced by the Sun’s position over a year. |
| Andromeda | Spiral galaxy nearest to the Milky Way in the Local Group. |
| Andromeda Galaxy | Spiral galaxy that is the largest in the Local Group. |
| Angular Diameter | Measure of the apparent size of an object in the sky. |
| Angular Momentum | Measure of rotational motion of an object, including celestial bodies. |
| Anomaly | Deviation from the expected orbit of a celestial object. |
| Antares | Brightest star in the Scorpius constellation. |
| Antimatter | Counterpart to normal matter, composed of antiparticles. |
| Antipodal Point | Point on the opposite side of a celestial body from another. |
| Apastron | Farthest point of an object’s orbit around another in binary systems. |
| Aperture | Diameter of the opening in a telescope or camera lens. |
| Aperture Synthesis | Technique combining signals from multiple telescopes to create high-resolution images. |
| Aphelion | Farthest point in a planet’s orbit from the Sun. |
| Apogee | Farthest point of an object’s orbit around another body. |
| Apollo | Series of US missions that landed astronauts on the Moon. |
| Apparent Magnitude | Brightness of a celestial object as seen from Earth. |
| Apparent Motion | Illusion of movement of celestial objects due to Earth’s rotation. |
| Appulse | Least apparent distance between one celestial object and another |
| Apsis | Point of an object’s orbit closest (periastron) or farthest (apastron) from a center of attraction. |
| Arcminute | Unit of angular measurement, 1/60th of a degree. |
| Arcsecond | Unit of angular measurement, 1/3600th of a degree. |
| Ascending Node | Point where an orbit crosses a reference plane from below. |
| Ascension | Right ascension (RA) is a celestial coordinate used to locate objects in the sky. |
| Asterism | Group of stars forming a recognizable pattern within a constellation. |
| Asteroid | Small rocky body that orbits the Sun in the asteroid belt. |
| Asteroid Belt | Region between the orbits of Mars and Jupiter with numerous asteroids. |
| Asteroseismology | Study of star interiors through observation of their oscillations. |
| Asthenosphere | Part of a planet’s mantle that allows tectonic plate movement. |
| Astrobiology | Study of life in the universe and its potential origins. |
| Astrochemistry | Study of chemical processes in space, especially in interstellar medium. |
| Astrograph | Telescope designed for astrophotography. |
| Astrolabe | Ancient instrument used to determine celestial positions. |
| Astrometry | Precise measurement of the positions and motions of celestial objects. |
| Astronaut | Trained individual who travels and works in space. |
| Astronomer | Scientist who studies celestial objects and phenomena. |
| Astronomical Calendar | Calendar based on astronomical events, like solstices and equinoxes. |
| Astronomical Clock | Timekeeping device that displays astronomical information. |
| Astronomical Twilight | Period when the Sun is between 12 and 18 degrees below the horizon. |
| Astronomical Unit (AU) | Average distance between Earth and the Sun (about 93 million miles). |
| Astronomy | Scientific study of celestial objects and the universe. |
| Astrophysics | Branch of astronomy dealing with the physical properties of celestial objects. |
| Astrostatistics | Application of statistics to analyze astronomical data. |
| Atmosphere | Layer of gases surrounding a planet or celestial body. |
| Auroras | Natural light displays in the Earth’s polar regions. |
| Axial Tilt | Angle between a celestial body’s rotational axis and its orbital axis. |
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