Voyager 1 crosses the final frontier

Voyager 1 has passed the termination shock, the final frontier of the solar system. Scientists had questioned whether or not this had happened already, but now everyone’s in agreement: Voyager 1 is on its way to interstellar space. In approximately 40,000 years, Voyager 1 will have its next encounter with a celestial body when it passes within 1.6 light years (9.3 trillion miles) of a the star AC+79 3888 in the constellation Camelopardalis.

Before it leaves the solar system, the probe will pass through a turbulent area of space where the solar wind compresses and gets both denser and hotter, whilst electrically charged particles and magnetic fields bombard the probe. When it leaves the solar system, Voyager 1 will experience the full onslaught of interstellar winds.

Voyager 1 is now the most distant human-made object in the Universe (with Pioneer 10 coming in second). At 8.7 billion miles from the Sun, it’s only 1/5,000th as bright as here on Earth. In 1998 Voyager 1 was so far from Earth that it took over 9 and a half hours for a radio signal to reach Earth. Voyager’s 20 watt signal is so faint that the power reaching NASA’s antennas is 20 billion times smaller than a digital watch battery’s.

The heliosheath is the area where the Sun’s solar wind collides with interstellar particles. The solar system is surrounded by a bubble of solar wind called the heliosphere. As the solar wind passes through the solar system it loses energy and speed, until it reaches the point where the speed suddenly drops as the influence of interstellar wind becomes stronger than the wind itself.

This point is called the Termination Shock. Once the Termination Shock has been passed, we enter the heliosheath, where the solar wind slows down and gets hotter and denser as the wind is pushed up against interstellar winds. The point where the solar wind meets interstellar space is known as the heliopause. Voyager 1 should encounter the heliopause in 10-20 years.

Both Voyager probes contain ‘golden records’, discs with instructions for any civilisation encountering the probes on how to play them. It is highly unlikely that anyone or thing will ever pick up the discs, and the exercise can be compared to putting a message in a bottle and throwing it into the ocean. Then President Jimmy Carter has a speech on the disc, on which he has this to say:

This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings. We are attempting to survive our time so we may live into yours.

On the disc are greetings in 55 languages, a selection of 115 images of earth and 90 minutes of music. Information on the contents of the disc (including the images and sounds) can be found here. A book on the disc, Murmurs of Earth: The Voyager Interstellar Record, contains most of the images along with information about the disc’s compilation.