Why the celestials bodies send out waves?

It's a scientific frontier in the space, a mysterious place outside the Earth, where all is an uncharted thing. This is uncharted because is a general discussion if it is a sound wave, sonic wave, or an interpretation.

They don't have to do a journey to investigate it, only send a ship with the capacity to grab radio waves and this are sent to a laboratory to process it. 

The terrain what the ship is sent is a dark and cold place, no light, no oxygen. The little ship has no human inside, it's only a machine to take photos and recipe waves. 

The main risk of this is the possibility to lose the ship, or it maybe destroys or lose the battery.