Sometimes, a rogue radio signal detected by astronomers is the result of aliens trying to make contact with Earth. Other times, it’s just a coworker trying to heat up her lunch.
This is what a group of researchers working at the CSIRO Parkes Observatory in Australia discovered after more than 15 years of studying fast radio bursts—intermittent pulses of radio waves from space that only last a few seconds—using the facility's 200-foot-wide radio telescope. Every once in a while, an errant signal would be detected, throwing a wrench in the team's data.
In a new paper, the lab group describes “perytons,” transient signals that look similar to the astrophysical pulses as detected through cold plasma. Mysteriously, these signals usually seemed to be picked up around lunchtime. Sadly, these weren't coming from aliens hoping to break bread with us. The radio pulses were generated by the microwave in the staff kitchen.
In the scientists’ words:
A peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explain all of the observed properties of the peryton signals.
There were three microwave ovens near the telescope, plus another two microwaves housed half a mile away. Even as these astronomers conducted tests hunting for the source of their mysterious radio waves, rogue microwaving got in the way. The researchers heated a cup of water in the microwave in the tower beneath the telescope while it was running, and were surprised to detect a single peryton. “The detection of radiation from the tower microwave would be very surprising as the tower is shielded on the windows and in the walls and the dish surface blocks the line of sight to the receiver in the cabin at the prime focus,” they write. They later discovered that someone else was using the microwave in the staff kitchen at the time. In a later trial, they opened the same microwave before it finished its heating cycle, producing three perytons. The scientists succeeded in creating these errant signals with their microwaves about 50 percent of the time.
On the bright side, the researchers were able to document notable differences between these decidedly terrestrial perytons and the supposedly cosmic fast radio bursts, giving them reason to believe that the FRBs are genuine astrophysical signals, not just the sign of someone’s ramen being ready. Still, astronomers working at Parkes may be eating cold lunches for a while.