Peng Jiang

In cold clouds of interstellar gas, carbon hides inside carbon monoxide (CO) molecules, like sugar dissolved in tea. But near hot, massive stars, this 'tea' boils: harsh radiation tears the molecules apart, and carbon escapes as lone atoms or ions.

In the dense family of old stars that astronomers call the cluster NGC 6791, a lonely radio beacon has been spotted — the pulsar PSR J1922+3745. Such objects are born when a massive star explodes and its core collapses into a tiny sphere the size of a city, which spins and emits radio waves like a rotating lighthouse beam.

Radio pulsar J1574+4703 behaves like a finicky lighthouse. Instead of shining steadily, it turns its radio beam on in short flashes and then falls silent for long stretches. Objects like this are called 'rotating radio transients', or RRATs for short.