A spinning object in our neighborhood of the galaxy is beaming powerful radio waves at Earth — and astronomers don't know what it is. The object is smaller than the sun and it must be spinning, because it only appears as an ultra-powerful radio signal for about one minute every 20 minutes, according to the Australian researchers studying it. The signal appeared and disappeared at this rhythm for several hours of telescope observations between January and March 2018. During its minute-long broadcasts, it was among the strongest radio signals in the sky.