There isn't a single word that perfectly describes something that is between celestial objects, as the term is quite broad. The most appropriate word depends on what specifically you're referring to. Here are some options:

General Terms:

* Interstellar: This refers to the space between stars.

* Interplanetary: This refers to the space between planets.

* Intergalactic: This refers to the space between galaxies.

* Cosmic: This is a general term for anything related to the universe.

* Celestial: This term refers to objects in the sky, including stars, planets, moons, etc.

Specific Terms:

* Void: This refers to a vast empty space, often used to describe the space between galaxies.

* Dust cloud: A concentration of interstellar dust and gas.

* Nebula: A cloud of gas and dust in space.

* Cometary debris: Fragments of comets that have broken apart.

* Asteroid belt: A region of space between Mars and Jupiter containing many asteroids.

More descriptive options:

* The space between... (followed by the specific celestial objects you're referring to)

* The region surrounding... (followed by the specific celestial object you're referring to)

The best word choice will depend on the context and what you are specifically trying to describe.