You would think that a 500-kilometer-wide solar jet stretching several thousands of kilometers high would be easy to spot. But because they are on the surface of the sun, these so-called spicules are close to the limits of optical resolution, which makes them difficult to observe. How and why solar spicules shoot out from the sun has confounded scientists ever since their discovery in 1877. Findings published today in the journal Nature solve the 127-year-old mystery.

Bart de Pontieu of the Lockheed Martin Solar and Astrophysics Lab (LMSAL) and his colleagues combined satellite data with high-resolution images taken by the Swedish Solar Telescope to investigate the solar jets and found that they tend to occur periodically--about every five minutes or so--at the same locations. "We developed a computer model of the sun's atmosphere to show that the periodicity of the spicules is caused by sound waves at the solar surface that have the same five-minute period," explains study co-author Robert Erdélyi of the University of Sheffield in England.

Spicules have a lot of mass, which means they play a large role in the flux of material going in and out of the sun's outer layer, or corona. Understanding the force behind the spicules should help researchers discern how the supersonic jets are tied to the solar wind, the stream of particles that reaches Earth's orbit.