The spacecraft detected a faint hum coming from deep space.

Imagine throwing a message in a bottle into the ocean, then waiting 48 years for it to wash up on a distant shore with news from an unknown land. That’s essentially what’s happening with NASA’s Voyager 1 spacecraft, except the ocean is space and the distant shore is 15 billion miles away.
The little spacecraft that could has been traveling since 1977, and it just sent back some pretty wild information. Scientists have discovered something they never expected to find in the emptiness between stars.