The winds of change are among us. According to data scientists have accumulated over 40 years and with the help of 11 different satellites, we have reason to believe the direction interstellar wind is “blowing” has changed direction.
First, it’s important to note that space isn’t really a true vacuum. There are tenuous clouds of material, along with random atoms/molecules all over the place. These interstellar clouds are measurable and are sensitive to other galactic forces, which can be very helpful for astronomers studying our position in the galaxy and the structure of the Milky Way.
As our sun moves through space, interstellar particles penetrate our heliosphere and enter the solar system. Our sun has been moving through this cloud for the last 45,000 or so years. Originally, scientists expected this cloud would be calm for the next few million years, but the change we’ve observed in the last few decades paints a very different picture. As I said before, the cloud is very thin. Priscilla Frisch from the University of Chicago describes the density of then cloud by saying, “If you took a handful of the air we breathe on Earth and stretched it out to the nearest star, it would have the same density as this cloud.” The fact that this change is happening so quickly tells one of two things; either we are passing through an unusually turbulent region or a solar system several hundred light-years away is creating a wake of turbulence for us.
Scientists know which direction the interstellar wind is blowing by measuring the direction the interstellar particles approach the solar system (the atom of choice is helium) . Such interstellar atoms are only harmful in the minds of Hollywood moviemakers, so we don’t have anything to worry about. The evidence for the changing winds primarily comes from NASA’s Interstellar Boundary Explorer (IBEX) – the spacecraft that so rudely showed us the Sun did not make a bow shock (which, lets face it, would be cool. There is a little hope yet). After IBEX data was compared to historical data regarding the interstellar winds, scientists noticed the discrepancy. The challenging part was figuring out if the intergalactic winds had actually changed direction or if we were just getting more accurate date from IBEX.
Ten satellites in total (not including IBEX) have provided measurements regarding the interstellar winds dating back to the 1970s. The missions that collected these measurements were launched by organizations from all over the world including the US, USSR (yes, as in the Soviet Union and not modern-Russia), the ESA, and Japan. These observations corroborate each other while IBEX is the odd one out. Eric Christian, one of the IBEX mission scientists, said, “The direction of the wind obtained from the most recent data does not agree with the direction obtained from the earlier measurements, suggesting that the wind itself has changed over time. It’s an intriguing result, which relied on looking at a suite of data measured in a bunch of different ways.”
Whereas scientists are still unsure as to what is causing this shift, the event itself still shows this cloud to be much more dynamic than we previously thought.