Voyager edges near interstellar space

A NASA update this week disclosed that the twin Voyager probes launched into space three decades ago are now poised at the edge of the solar system. Over the course of the intervening years, the two crafts have sent back a trove of data and pictures from their visits to our neighboring planets.

This image sent back by Voyager 1 offers a look at the active plume of Loki on the limb of Jupiter's moon, Io.

Both Voyagers have since left our solar system and are now sailing somewhere in what astronomers call the heliosphere, an interstellar medium composed of solar plasma and magnetic fields.

It's still unclear how much farther they will need to travel in order to reach interstellar space - but they are getting close. "The heliosheath is 3 to 4 billion miles in thickness," according to Ed Stone of the California Institute of Technology in Pasadena, who has been Voyager Project Scientist since 1972. "That means we'll be out within five years or so."

Voyager 1 has visited Jupiter and Saturn, while Voyager 2 has flown past Jupiter, Saturn, Uranus and Neptune. This graphic is an artist's concept showing the two Voyager spacecraft.

An artist's rendering of the Voyager encountering Jupiter, Saturn, Uranus and Neptune. Both Voyager spacecrafts are identical. Voyager 2 was launched on Aug. 20, 1977. Voyager 1 was launched on Sept. 5, 1977.

The mission was conceived to exploit a rare geometric arrangement in the late 1970s and the 1980s which allowed for a four-planet tour for a minimum of propellant and trip time past Jupiter, Saturn, Uranus and Neptune. This particular layout occurs about every 175 years.

Between them, the two craft have racked up serious mileage including visits to the giant outer planets of the solar system, 48 of their moons, as well as the rings and magnetic fields those planets possess.

On the odd chance that the Voyagers meet someone - some thing? - that can understand it, each craft is hauling with it a Golden Record, containing music, sounds and scenes from Earth, as well as greetings from Earth in 55 languages.

Color mosaic of Triton photographed by Voyager 2 during a pass by the Neptune system. Triton, the biggest satellite of Neptune, also is just one of only three objects in the solar system known to have a nitrogen-dominated atmosphere. The others are Earth and Saturn's moon, Titan.

Earlier this year, Voyager 1 was estimated to be about 17.5 billion 10.9 billion miles away from the sun. Voyager 2 is about 8.8 billion miles away from the sun.

A screen grab of an animation displaying streams of charged particles inside the bubble around our sun as well as those found in interstellar space.

This is how our solar system would look like to a visitor in interstellar space. The colors map the intensity of the magnetic field around our solar system. Red indicates the highest intensity field and blue, the lowest. You can make out the recent trajectory of Voyager 1 by following the thick red line. The thick magenta line marks the path taken by Voyager 2.

A map of the heliosphere based upon data sent back from NASA's Cassini spacecraft. The regions with the highest intensity of particles created from the mingling of interstellar medium and solar wind are red; those with the lowest intensity of particles are blue.

Map of the interactions occurring at the edge of the solar system based on measurements taken by the two Voyagers during their journeys out of our solar system.

The first-ever shot of the Earth taken by Voyager 1. The narrow-angle color image was part of a wider "portrait" of the solar system taken from a distance of more than 4 billion miles from Earth.