That's a great question! It depends on what you mean by "piece of matter" and "space."

Here are some possibilities:

General:

* Anything moving in a vacuum: This could be a particle, a dust grain, a rock, a spacecraft, or even a planet.

* Anything moving relative to another object: Even something on Earth is technically moving through space, as the Earth orbits the Sun.

More specific:

* Meteoroid: A small piece of rock or dust in space.

* Asteroid: A larger rocky body in space.

* Comet: A ball of ice and dust that orbits the Sun.

* Satellite: An artificial object that orbits the Earth or another celestial body.

* Spacecraft: A vehicle designed for travel in space.

Can you give me more context about what you're interested in? Knowing more will help me give you a more precise answer! 😊