Voyager 1, launched way back in 1977, is still giving us Science, far away beyond the influence of the Sun. In the past few years, the spacecraft has passed the boundary between the Solar System and the Interstellar Medium, the so called Heliopause. This has given scientists the first ever direct look at the Space between stars.
Since then, Voyager has felt some interesting shock waves, which are being referred to as ‘Tsunami Waves.’
When the Sun emits a Coronal Mass Ejection, the charged particles travel through the Solar System as a pressure wave. When this wave hits the Heliopause and the charged particle plasma of interstellar space, it creates a shock wave, similar to a large ripple.
“The tsunami causes the ionized gas that is out there to resonate — “sing” or vibrate like a bell,” said Ed Stone, project scientist for the Voyager mission based at California Institute of Technology in Pasadena. “The density of the plasma is higher the farther Voyager goes. Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet.”
Voyager has felt three such waves, and the current one has been ongoing since February 2014! During this time, Voyager has travelled 400 Million Km through Space.
The second plasma wave in December 2013 helped scientists verify once and for all that Voyager had left the Heliosphere, the solar wind bubble surrounding the Sun and Planets in the Solar System. They found that the waves ‘ring’ in lower frequencies at higher plasma densities, and measured a density 40 times higher than when Voyager was within the Heliosphere.
Amazing that even in deep Space, Earthbound Physics such as fluid dynamics can help us solve mysteries and piece together our knowledge of the Cosmos.