[RFI] Radio signals puzzled astrophysicists for 17 years. They were coming from a microwave oven.

[Steve Sacco NN4X]

[ SNIP ]

Since 1998, astrophysicists at Australia's Parkes Observatory have been 
detecting mysterious bursts of radio waves (named "perytons") that 
seemed to emanate from all parts of the sky. They lasted for just 
fractions of a second and happened once or twice a year.

Most believed they came from somewhere quite nearby (perhaps resulting 
from lightning strikes), but the bursts had some characteristics that 
made it seem like they'd traveled millions of light-years from distant 
galaxies or other astronomical objects.

The truth, as recently discovered by graduate student Emily Petroff of 
Swinburne University of Technology, is decidedly more mundane. It turns 
out the signals were generated by someone at the facility opening the 
door of a microwave oven while it was still running.
[ /SNIP ]

http://www.vox.com/2015/5/5/8553609/microwave-oven-perytons