NASA's Voyager 1 spacecraft has left the solar system. The space agency announced Voyager 1 has entered into interstellar space and is currently 12 billion miles from the Sun. According to NASA, Voyager 1 left the solar system and entered interstellar space in August 2012.
NASA announced the historic milestone as Voyager 1 is the first man-made object to go beyond our solar system and into interstellar space. Voyager 1 is currently in a transitional region just outside of the solar system, notes NASA. The team of researchers behind the study, led by Don Gurnett, from the University of Iowa, Iowa City, analyzed the data collected by Voyager 1 and determined that the spacecraft was in interstellar space. “The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we've all been asking -- 'Are we there yet?' Yes, we are,” said Gurnett in a statement.
The biggest concern, when it came to confirming Voyager 1’s entry into interstellar space, for researchers determining where the sun’s influence, or the heliosphere, ended. The heliosphere is a massive bubble that surrounds the solar system and stretches well beyond Pluto.
According to NASA, Voyager 1 did not have a plasma sensor and researchers could not analyze the composition of the surrounding environment. One of the ways to determine if Voyager 1 left the solar system was to look for the presence of solar wind particles, indicating the spacecraft was still inside the heliosphere, and the presence of galactic particles, indicating Voyager 1 had reached interstellar space.
Gurnett’s team had to find a way to analyze particles surrounding the spacecraft and was able to do so with the help of a coronal mass ejection, or CME. A CME is a massive burst of solar wind and magnetic fields ejected into space, notes NASA. The CME occurred in March 2012 and was felt by Voyager 1 in April 2013.
Using the onboard plasma wave instrument, which detects the pitch of the particles in order to determine the density of the plasma, Voyager 1 collected the data needed by researchers. Based on the data from the CME, the plasma surrounding Voyager 1 was 40 times denser than that of the plasma found in the outer layers of the heliosphere, a number that was consistent with earlier predictions of the plasma density in interstellar space. The results were confirmed when Voyager 1 collected another set of data in October and November 2012, reports NASA.
Based on these calculations, the researchers concluded Voyager 1 entered interstellar space in August 2012. Gurnett said, “We literally jumped out of our seats when we saw these oscillations in our data -- they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble.”
There was some controversy prior to the official announcement from NASA as a recent research paper concluded Voyager 1 had already left the solar system. The study, led by Marc Swisdak from the University of Maryland, used a new model that indicated Voyager 1 had actually left the solar system more than a year ago. According to Swisdak, the transition zone between the heliosphere and interstellar space, known as the heliopause, the boundary between solar wind and interstellar wind, was porous. The model would explain the lack of solar particles but not a change of direction in magnetic field, something researchers believed would happen as Voyager 1 entered interstellar space. NASA confirmed Voyager 1 exited the heliopause around the same time as Swisdak’s model predicted.
After 36 years and a historic milestone under its belt, Voyager 1 will continue its scientific mission and the space agency is excited about the new data the spacecraft will collect. Suzanne Dodd, Voyager project manager, said in a statement, “We expect the fields and particles science instruments on Voyager will continue to send back data through at least 2020. We can't wait to see what the Voyager instruments show us next about deep space.” The data collected by Voyager 1 will provide new insights into the heliosphere, the furthest reaches of our solar system and interstellar space.
There is no set time for when Voyager 1 will totally be free from the influence of the sun but NASA is receiving regular transmissions from the spacecraft. Voyager 1’s twin, Voyager 2, is older by 16 days and spent time observing Jupiter, Saturn, Uranus and Neptune. Voyager 2 will be the next spacecraft to enter interstellar space but researchers are not sure when it will exit the solar system.
In addition to its scientific tools, Voyager 1 is carrying a special message from Earth on a golden record. The 12-inch record includes instructions, necessary for any interstellar travelers, 115 encoded images from Earth, music, sounds and greetings from the most ancient language, Akkadian,t to modern languages, including Wu, a Chinese dialect. Carl Sagan chaired the committee that selected the contents of the golden record and said, “The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet,” reports NASA.
A video of Voyager 1's mission, courtesy of NASA's Jet Propulsion Laboratory, can be viewed below.