It's not everyday that spacecraft reveal something like this, but thanks to the U.S. Department of Defense's Space Test Program 72-1 and SOLRAD 11B, NASA's Mariner, the Soviet Prognoz 6, IBEX, STEREO, ACE, MESSENGER, Ulysses and Japanese Aerospace Exploration Agency's Nuzomi, we now know that the interstellar wind changed direction over the course of the last 40 years.
According to a news release from NASA, this information is invaluable to scientists trying to answer such questions as: what is our current location in the cosmos?
Evidence of the interstellar wind flowing into the heliosphere is one of several ways that scientists can get a glimpse of what resides just beyond our own home, in the galactic cloud through which the solar system moves. According to NASA, the heliosphere and an interstellar cloud zip past each other at a speed of approximately 50,000 miles per hour. This movement generates a wind of neutral interstellar atoms flowing past our planet, of which helium is the simplest to measure.
In January 2012, IBEX revealed that the interstellar wind was accessing the heliosphere from a different direction than had been determined by the space agency's Ulysses mission in the 1990s. Had the wind direction itself changed or was the space agency's latest technology offering more accurate results?
The study's authors looked at data from the aforementioned spacecraft and discovered that the direction of the wind obtained from the latest data does not match up with the direction of the wind obtained from the earlier measurements, implying that the wind itself has changed direction over time.
According to NASA, various sets of observations provided by the spacecraft relied on three different techniques to determine the direction of the incoming interstellar wind. Click here to read an in-depth explanation of these three techniques.
The data from these spacecraft reveals that the direction of the interstellar winds has altered approximately four to nine degrees over the last 40 years.
Although the exact reason for the shift in wind direction is still unknown, the study's authors think that new data should eventually explain the shift.
To learn more about this study, check out the published version in the journal Science.
