The signal that returns every 16 days
The account
A signal with such a regular rhythm could only be a beacon programmed by someone.
What investigators found
The cycle may come from an orbit in a binary system or from the wobble of a neutron star's axis.
The story
Most fast radio bursts happen only once. FRB 20180916B, detected by the Canadian radio telescope CHIME, was different. In 2020, researchers announced that it followed a pattern: for a few days it emitted bursts, then it went silent, and the full cycle repeated every 16.35 days. The source was pinpointed in a spiral galaxy about 500 million light-years away.
A cosmic clock like that raised the inevitable question online: could it be an artificial beacon? Astronomers point to simpler paths. The source may be orbiting a companion star, and we can only see the bursts during a certain phase of that orbit. Another hypothesis is a magnetar whose axis wobbles like a spinning top. The exact mechanism is still being studied.