* Asteroid: A small, rocky body that orbits the Sun.
* Algol: A binary star system in the constellation Perseus.
* Andromeda Galaxy: A spiral galaxy that is the closest major galaxy to the Milky Way.
* Antlia: A constellation in the southern celestial hemisphere.
* Arcturus: A bright orange giant star in the constellation Boötes.
* Asterism: A recognizable pattern of stars that is not a constellation.
* Aurora: A natural light display in the sky, predominantly seen in the high-latitude regions (around the Arctic and Antarctic).
There are likely many other celestial bodies that start with "A" depending on how broadly you define the term "celestial body".
