Thursday, October 4, 2012

What Voyager is doing now

In our last article about Voyager, we discussed Voyager's last photo from space. After taking that photo which was the end of the grand tour, it seemed reasonable to shut down the mission and let the spaceships continue their eternal journey in space. However, since the spaceships' condition was still very good, most of the systems still functioning and their location was the furthest any object had arrived it seemed sensible to find a new mission for Voyager and not let it waste in space.
Every end is a new beginning and the end of the "Grand Tour" was the beginning of VIM - "Voyager Interstellar Mission". You might have heard on the news that Voyager left or is about to leave the solar system. This is not accurate and we need to first determine where the solar system ends. If our criteria for the edge of the solar system is the distance at which the sun gravity has little effect on celestial bodies, Voyager is still in the inner part of the solar system. The influence of the sun gravity reaches to a distance of about 1 light year from the sun, to the end of the Oort cloud.
A definition which is better for our purpose, is the border of the magnetic field of the sun. The sun's magnetic field moves with the sun. As it is illustrated in the diagram below, the magnetic field seems like a bullet advancing with the sun. It travels with and in front of the sun and stretches to a great distance behind it. Charged particles from the sun (a.k.a "Solar wind") travel very fast, they start to slow down when they meet other charged particles coming from space (a.k.a "Space wind"). The area where Voyager 1 is currently traveling is the place where these two "winds" meet ("wind" is used as a metaphor).

Voyager Interstellar Mission
Voyager Interstellar Mission. NASA
In this diagram, the inner circle is the Solar system with its 8 planets (as we said before, there are other objects further away which orbit the sun). The Heliosphere, the sun's atmosphere, reaches beyond and behind the sun, and the Heliosheath is the area where Voyager 1 is currently traveling.
The size of the Heliosheath is unknown and it is changing constantly. The scientists hope that Voyager will be able to cross it and reach the area of the bow-shock. Voyager's energy supply (we will deal with this matter in our next article) will last for the next 10-15 years. In order to conserve energy, all unnecessary instruments were shutdown long ago, and only 5 systems are still functioning. These systems include the communication system, the magnetometer and other instruments to measure the speed and direction of charged particles.
What Voyager discovered is that particles from the sun's direction become slower and slower, and particles not from the sun's direction become more and more common (and with greater speed). This means that Voyager is getting nearer to the area where the majority of particles will not be from the sun (and only in that sense, leaving the solar system). So, it is now a race against time, to get as far as possible before all Voyager's energy is used. The current distance of Voyager 1 from the sun is 120 AU (astronomical unit - the distance from the sun to earth - 150,000,000 KM) and its speed is 3.6 AU per year. In 10 years it will reach a distance of 150 AU from the sun, and if it will still function we will learn a lot about the strange conditions at that far place. Voyager 1 is the front lab of humanity and it provides sci-fi enthusiastic some food for thought  about spaceship travels to other stars and planets.

See Voyager exact distance from earth and sun

Previous articles
Voyager - The grand tour
Voyager's last photo