Where Does Our Solar System End?

Apr 13, 2013 By Sarah Charley
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[This article is a continuation of Part 1 here]

Where exactly is Voyager 1 in space? Just like you would see the landscape change as you drive across the country, scientists measure changes in space to gauge the location of Voyager 1 and see if their theories about the solar system match reality.

Leaving the solar system means leaving the influence of the sun. The sun has three main attributes: the solar wind, a gravitational pull, and a magnetic field. Voyager 1 and 2 collect data about these attributes as they coast through space. By studying this data, scientists can piece together what space looks like far away from our sun.

Solar Wind

The sun is constantly shooting off high energy particles into space. These particles—called the solar wind—cause the Northern Lights on Earth, and mark important boundaries in space. The first thing to change as the solar system meets interstellar space is the speed of the solar wind. 

The meeting of the solar wind and the interstellar wind at the edge of the solar system is like two rivers converging. When the fast “streams” of particles emanating from our sun intermingle with the slow and sluggish interstellar wind, they swirl, bubble and slow. The convergence is called the termination zone, and the region of swirling particles is the heliosheath.

Scientists suspect Voyager is somewhere between the turbulent heliosheath and the placid heliopause— a region where the swirling stops and only particles in interstellar space are detectable. But because no spacecraft has ever entered the outer regions of our solar system, scientists do not know what to expect when Voyager 1 reached this odd intersection in space. 

Magnetic Field

The sun is composed of charged particles, and these charged particles create a huge magnetic field. Because the sun is constantly spinning, its magnetic field is also spinning. Unlike the magnetic field created by bar magnets, the sun’s magnetic field twists like the dress of a spinning figure skater.

Recently, NASA scientists clarified that the end of the solar system will be marked by a change in the direction of the magnetic field. However, they are unsure what this change will look like or when it will occur. Initially they suspected the union of the sun’s magnetic field and the interstellar magnetic fields would be smooth and simple, but this meeting is much more twisted and tangled than expected, probably because of gas and dust particles interrupting the magnetic fields.

Gravity

But even after the stream of charged particles dissipates and the magnetic field disappears, scientists suspect that the sun’s gravity will continue to effect objects as far away as two light years (or 125,000 times the distance between the earth and the sun.) Scientist also theorize that a spherical cloud of icy objects—called the Oort cloud—encompasses the solar system and marks the edge of the sun’s gravitational pull. However, scientists think that it will take another 14,000 to 28,000 years before Voyager 1 breaks through this theoretical sphere and leaves the last lingering influences of our sun forever.