Where does the solar system end? Voyager 1 probe to find out, eventually. (+video)
Launched on Sept. 5, 1977 and now more than 11 billion miles from the sun, the Voyager 1 probe was expected to be exiting the solar system by now. But it seems the edge is farther out than scientists thought.
NASA's Voyager 1 spacecraft, which launched 35 years ago today (Sept. 5), surprisingly may have far more to travel before it leaves the solar system, researchers say.
How much more is up for debate. The scientists say their new finding suggests much about the outer reaches of the solar system remains unknown.
Voyager 1, which left Earth on Sept. 5, 1977, is about 11.3 billion miles (18.2 billion kilometers) from the sun. Meanwhile, Voyager 2, which launched 16 days earlier on a longer trajectory, is approximately 9.3 billion miles (14.9 billion km) from the sun.
NASA launched the twin Voyager 1 and Voyager 2 spacecraft to explore the outer planets in our solar system. Researchers had thought the probes, which are still occasionally beaming back data, might be exiting the solar systemby now – but the direction of the solar wind is telling them otherwise.
One way to think about the edge of the solar system is to measure it in terms of the solar wind, the stream of energetic particles pouring from the sun. The area dominated by the solar wind is known as the heliosphere.
The distant region where the solar wind slows as it begins to run into interstellar gas and dust is known as the heliosheath. The mysterious boundary where the solar wind finally ends and the interstellar medium begins is called the heliopause.