Basic Astronomy

It is official: Voyager 1 finally out of Solar System

13 September 2013: Now it is official. Scientists confirmed that NASA's 36-year-old Voyager 1 probe finally went out of Solar system and become the first human made object to reach interstellar space beyond Solar system.

For over a year, scientists are debating whether Voyager 1 has left the Solar system or not.

Presently Voyager 1 probe located about 12 billion miles (19 billion kms) away our Sun.

Scientists found new and unexpected data which indicates that Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Right now, Voyager 1 is in a transitional region immediately outside the solar bubble, where some effects from our Sun are still evident.

On 13th September 2013's edition of the famous scientific journal Science, a report on the analysis of this new data from Voyager 1 is published by Don Gurnett and the plasma wave science team at the University of Iowa, Iowa City.

Voyager project scientist Ed Stone said "Now that we have new, key data, we believe this is mankind's historic leap into 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". NASA’s associate administrator for science John Grunsfeld said "Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavors". He also added "Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey".

Since Voyager 1 is not carrying a working plasma sensor, scientists needed to use indirect way to measure plasma environment of the probe to be sure about its location. Luckily, scientist got a unexpected gift from Sun to confirm location of Voyager 1. A coronal mass ejection erupted from the sun in March 2012 which arrived at Voyager 1's location 13 months later, in April 2013 provided scientists the missing data they needed. When this ejection from Sun reached Voyager 1, the spacecraft starts to vibrate. On April 9 2013, Voyager 1's plasma wave instrument detected this vibration. Scientists determine the density of the plasma from the nature of the oscillations. The result showed that the surrounding plasma of Voyager 1 is 40 times denser than plasma density of outer layer of the heliosphere. In interstellar space this kind of plasma density is expected.

After finding this piece of evidence to confirm that Voyager 1 is presently moving outside solar system, scientists checked previous data and found an earlier, fainter set of oscillations in October and November 2012. By extrapolation of measured plasma densities from both of these events, scientists predict that Voyager 1 first entered interstellar space in August 2012.

"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," Gurnett explained. "Clearly we had passed through the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma" he further added.

Scientists are not sure when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from our Sun.

Scientists expect the instrument will work till 2020 after which scientists will start turning off instruments and around 2025 the probes will be completely out of power and will fall silent.

Another probe Voyager 2 is moving in another direction of the Solar system and it is expected that it will move out of Solar system after five to seven more years.

Both of the Voyager probes were launched 16 days apart in 1977 to study the outer planets of the solar system. Both of these probes flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. These probes contain gold phonographic records etched with greetings, music, sounds and images from Earth.

Voyager mission controllers still receive data from Voyager 1 and Voyager 2 every day, though the emitted signals are currently very dim due to large distance between these probes and Earth. Data from Voyager 1's instruments are captured by 34 and 70 meter NASA Deep Space Network stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours to reach Earth.

Voyager 1 will encounter a star after about 40,000 years when it will fly about 1.7 light years away from a star AC +79 3888 which is located in the constellation Camelopardalis.

Voyager 1 is traveling about 1 million miles (1.6 million km) a day.

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