U.S. astronomers have determined that radio waves generated by solar particles high above the Earth travel into space in a narrow plane. The findings by University of Iowa scientists refute the decades-long assumption that such radio waves disperse in an ever-widening cone. The researchers studied radio waves called the Auroral Kilometric Radiation generated by the same solar particles that produce auroral lights. The scientists said they analysed data collected by instruments on the European Space Agency's four Cluster spacecraft.
The first thing an alien race is likely to hear from Earth is chirps and whistles, a bit like R2-D2, the robot from Star Wars. In reality, they are the sounds that accompany the aurora. Now ESAs Cluster mission is showing scientists how to understand this emission and, in the future, search for alien worlds by listening for their sounds.