Where does the solar system end? Voyager 1 probe to find out, eventually.

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/JPL-Caltech
NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space, which scientists are calling the stagnation region. This image shows that the inner edge of the stagnation region is located about 10.5 billion miles (16.9 billion kilometers) from the sun. The distance to the outer edge is unknown.

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.

Past research suggested the Voyager probes were entering an unknown part of the heliosheath (dubbed the "transition zone" or the "stagnation region") where the flow of solar wind had apparently calmed down. Scientists thought that by now Voyager 1 would start to see the solar wind deflected from its straight outward path into a more northward or southward manner as it curved to form the heliopause. [Photos from NASA's Far-Flung Voyager Probes]

Now researchers using data from the Voyager 1 spacecraft find the probe is not yet close to the heliopause.

"The implication is that the flow of solar wind plasma in the heliosheath is more complex that we had expected," study lead author Robert Decker, a space physicist at Johns Hopkins University, told SPACE.com.

Decker and his colleagues requested that the Voyager project team rotate Voyager 1 periodically to see if the solar wind was in fact getting deflected in a northward or southward manner. They found no evidence of deflection in the zone the probe was zipping through.

It remains uncertain how much farther outward the transition region extends, researchers say. As to when Voyager 1 might actually leave the heliopause, "opinions vary on this," Decker said. "Based on the changes we have seen in the Voyager 1 data during the past year, I would expect that Voyager 1 will cross the heliopause within one year."

Decker and his colleagues detail their findings in the Sept. 6 issue of the journal Nature.

NASA's Voyager 1 and Voyager 2 spacecraft amazed astronomers with close-up views of the gas giant planets Jupiter, Saturn, Uranus and Neptune during their tag-team mission. Voyager 2, which launched Aug. 20, 1977, is currentlyNASA's longest running mission ever.

Each Voyager probe carries a golden record with a collection of sights and sounds from Earth, just in case the spacecraft are discovered by intelligent beings in interstellar space.

The recordings include 117 images of Earth, animals and humans, as well as greetings in 54 languages, with a variety of natural and human-made sounds like storms, volcanoes, rocket launches, airplanes and animals. The collection was chosen by a committee chaired by Cornell University astronomer Carl Sagan.

Follow SPACE.com on Twitter @Spacedotcom. We're also on Facebook and Google+.

Copyright 2012 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Where does the solar system end? Voyager 1 probe to find out, eventually.
Read this article in
https://www.csmonitor.com/Science/2012/0905/Where-does-the-solar-system-end-Voyager-1-probe-to-find-out-eventually
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe