Signals that baffled astronomers for 17 years traced to observatory's microwave oven

For 17 years, astronomers at a well-known Australian radio telescope known as "The Dish" had not been able to figure out the source of a strange, vexing interference.

Now they've solved the mystery, and the culprit was right under their nose rather than in a galaxy far, far away.

Simon Johnston, head of astrophysics at the CSIRO, the national science agency, told the Guardian that a couple of times a year signals known as perytons were detected "within five kilometers" of the Parkes Observatory in New South Wales. The first theory was that the perytons were caused by local lightning strikes.

On New Year's Day, the observatory installed a new receiver to monitor the interference, and it detected strong signals at 2.4 GHz.

Two point four gigahertz is the signature of a microwave oven.

When scientists tested the facility's lunchroom microwave, no perytons were found — at least not at first.

But when the door of the microwave was opened while food was heating — as one might do to check on a reheated dish — bingo! Perytons spilled out like microwaved popcorn.

Complicating matters was that the Dish only registered the perytons when it was pointed at the microwave.

Astronomers generally operate the telescope remotely, but several maintenance workers are on the site during daytime hours. Little did they know that reheating their coffee created an enigma that would remain unsolved for almost two decades.