NASA’s Voyager 1, which left Earth on 5th September 1977 reached the news yesterday as the first man made object to leave our solar system and enter interstellar space, although scientists believe it actually left our solar system in August 2012!
In mid 2012 NASA knew something was up. They had noticed that Voyager’s instruments had started to see a drop off in the numbers in energetic particles coming up behind it from the Sun. At the same time they had also noticed a sharp increase in the low energy cosmic rays hitting the detectors on the front of the probe. In March this year a press release was placed into a journal by the American Geophysical Union saying: “Voyager 1 has left the solar system, sudden changes in cosmic rays indicate” Although at the time NASA’s mission team for Voyager-1 denied this. 
Even though scientists are receiving the data about the probe now, in the next decade or so will go offline; however on board Voyager is a golden record which has a selection of multicultural greetings, photos, songs and even directions to earth in case the Voyager is spotted by any outer space intelligence!
Surrounding the solar system is a plasma “bubble” which is basically ionised gas. This is one of the most densest, slowest moving charged particles in space. This plasma is of huge significance to whether Voyager 1 has actually left the solar system. The image above shows a diagram of where scientists believe Voyager 1 actually is.  As the probe went through the plasma, the probe recorded an “unearthly howl” which you can hear if you click on the third reference. These sounds would be inaudible in space but the sounds are at frequencies that we can hear. The pitch of these oscillations helped scientists to determine the density of the plasma and therefore whether the probe has entered interstellar space, which it has.
Voyager travels at a maximum speed of 62,136 km/h and has travelled around 13 billion miles, this BBC interactive gives a fantastic idea of Voyager’s speed: www.bbc.co.uk/news/science-environment-21937524 . If clicking on the link doesn’t work try copy-pasting it into the browser box at the top of the internet page. Follow @NASAVoyager on twitter for more updates on the Voyager Space Probe.
References: 1. http://www.bbc.co.uk/news/science-environment-24068221 Accessed 13/9/13 2. http://www.jpl.nasa.gov/news/news.php?release=2013-278 Accessed 13/9/13 3. http://uk.news.yahoo.com/nasa-probe-hears–shriek–in-space-as-it-leaves…