Confirmed: Voyager 1 Has Gone 'Interstellar'
Three separate shock waves from solar activity have helped NASA confirm that the Voyager 1 unmanned craft has made its way into interstellar space - drifting past the outer layers of the Sun's heliosphere.
Voyager 1 had been coasting on a pre determined course through the outer heliosphere of Earth's Sun over the past two years, helping NASA scientists collect data that would lead them to discover that the Sun's atmosphere - called the corona - is actually far larger than originally thought.
Then, in April 2013, the craft detected a shock wave from a solar coronial mass ejection (CME). This was the first indication to scientists that Voyager had likely entered interstellar space. According to NASA, interstellar space begins when the Sun's massive hemisphere - a bubble of solar particles and magnetic fields that surround the whole star - ends. However, it is important to point out that while Voyager 1 may be past the Sun's direct influence, the crafts till very-much remains in the solar system, which is surrounded by a ring of comets known as the Oort Cloud.
As of July 8, NASA's Jet Propulsion Laboratory (JPL) confirmed that Voyager is indeed just entering interstellar space, determining that two other CME plasma waves have disturbed particles around Voyager 1 since it left the hemisphere.
"All is not quiet around Voyager," said Don Gurnett, the principal investigator of the plasma wave instrument on Voyager, which collected the definitive evidence that Voyager 1 had left the sun's heliosphere. "We're excited to analyze these new data. So far, we can say that it confirms we are in interstellar space."
According to the space agency mission team cosmic rays from nearby stars in the Milkyway Galaxy are pushed around "like buoys in a tsunami" during moments of increased Sun activity, such as CMEs, allowing for them to be analyzed more easily. Plasma electrons in these waves can help reveal the location of Voyager based on their density. The 2013 CME waves helped reveal that Voyager 1 was now surrounded by plasma 40 times denser than previously seen - a certain sign that it is in interstellar space.
Voyager 1 was launched 16 days after its twin Voyager 2 in 1977, but Voyager 2 was sent on a longer loop around the Sun. That second spacecraft is expected to reach interstellar space in a few years.