In 1977, two unmanned space crafts were launched to explore space and report back to NASA with information about the major planets: Voyager 1 and 2. Within the first 12 years of launching, both Voyagers returned information about Jupiter, Saturn, Uranus and Neptune. Now though, after 36 years of being in space, NASA is extremely proud to announce that Voyager 1 has left the solar system.
In actual fact, although NASA announced the Voyager’s departure from the solar system quite recently on September 12th 2013, it appears the leaving date itself was way back in 2012 – August 25th to be precise. So why the big delay on the celebrations?
At the moment, Voyager 1 is over 11 billion miles or 17 billion kilometers away from Earth. NASA can’t see the spacecraft at all. All that is visible is a radio signal that is being bounced back to Earth from the Voyager which looks like a pale blue light.
Unlike travelling out of town, there are no signs which tell concerned onlookers exactly where the Solar System ends. Instead, scientists must look for clues in the direction and number of cosmic rays as well as a difference in magnetic fields. However, the signs just didn’t appear to be there. It wasn’t until information from a plasma blast that hit the voyager in April 2013 that NASA had any indication that the Voyager was outside of the solar system.
The Clue Is In The Plasma
In March 2012, the sun emitted a huge blast of plasma which took 13 months to hit the Voyager. When it did hit though and the information was read by NASA experts, they were astonished to see that the density of the plasma was 40 times what they expected it to be. In short, it was the density of plasma they expected to find outside of the solar system.
Following this discovery, NASA quickly began to backtrack and look for any other signs of interstellar activity and found another similar event back in October to November the same year. A rise in tone from the plasma instrument on the voyager indicated that the spacecraft left the solar system on August 25th 2012 which is now known as the day when the first man made object went into interstellar space. Officially.