NASA's Juno spacecraft entered Jupiter's orbit last night. On its way there, though, the craft was able to record some interesting sounds that seem to belong on the 2001: A Space Odyssey soundtrack. Many articles are describing the sound as a "creepy" roar. While this descriptor is pretty accurate, the sounds are actually easily explained (spoiler: its still not aliens).
The noise is actually the 'bow shock' caused by the spacecraft's entry into the planet's magnetic field that protects the planet from solar winds. You can hear it in the video from NASA below:
When supersonic solar winds are suddenly slowed down and heated up as they plough into the gas giant's magnetosphere, they produce a bow shock. This is comparable to the sonic boom produced when an aircraft goes faster than the speed of sound on Earth. The compression waves produced combine to form a shockwave.
The eerie-sounding recording lasted for around 2 hours, which is a great feat considering that the spacecraft is traveling at the speed of 241,000 km/h (150,000 mph).
Who knows what other sounds we are missing when our spacecraft aren't around to capture the noises of the universe.