It took scientists 17 years to figure out that a microwave oven was causing interference with a radio telescope

Flickr/Chris Kelly

For close to 17 years, astronomers at Parkes Observatory in Australia searched in vain to track down the source of interference with their observations.

Until early this year, when they discovered that it was coming from the microwave oven in the observatory's kitchen.

The observatory is home to the country's best-known radio telescope, which is used to measure radio signals for signs of extraterrestrial life.  The interference, which began in 1988, was soon determined to be nearby, The Guardian is reporting, but the source remained a mystery.

Simon Johnston, head of astrophysics at the CSIRO, Australia's national science agency, told the newspaper that the radio signals, called perytons, "were reasonably local, say within 5km of the telescope" and appeared only once or twice a year. They were believed to be from lightning strikes. 

That changed when a new receiver installed at the site measured radio signals at 2.4 GHz, the same frequency as a microwave oven, he explained.

Getty ImagesThe radio telescope at Parkes Observatory.

Scientists honed in on the microwave but still had trouble pinpointing it as the real cause of interference until opening the door before it finished heating the food.

"If you set it to heat and pull it open to have a look, it generates interference," said Johnston.

The findings were published in a scientific paper, according to The Guardian.

Parkes Observatory was completed in 1961. The 210-foot moveable dish was one of the many used to both track and televise the Apollo 13 emergency landing in 1970.