The Heliosphere
(Photo : NASA) An illustration of the position of the twin Voyager space probes.

The edge of the solar system remains to be a mystery for mankind, but recent data sent back by NASA spacecraft Voyager 2 provides enough evidence for astronomers to formulate a conclusion regarding the characteristics of the heliosphere.

BEYOND THE SOLAR SYSTEM

The heliosphere lies at the edge of the solar system, exactly twelve billion miles away from Earth. It is considered as some elusive boundary that serves as a marker to where the sun's reach ends and where the interstellar space begins.

It is an exciting time, indeed, because this is the first time that a man-made spacecraft reached this region of space and beams back data that let astronomers piece together a picture of the edge of the system. 

SHAPE OF THE HELIOSPHERE

The heliosphere serves as a cosmic weather front, a sort of a distinction between the solar system and interstellar space. In this region, charged particles are moving away from the sun at supersonic speed. These charged particles will then meet the cooler interstellar wind, which came from a supernova that must have exploded millions of years ago. 

Before the arrival of the Voyager spacecraft, it was thought that these solar wind eventually fade into space. It was thanks to Voyager 1 that scientists found out the presence of a boundary. Within this boundary, a sudden drop in the temperature can be experienced along with an increase in the density of the charged particles.

The Voyager 2 spacecraft, on the other hand, brought back measurements that provided insights on the components of the heliosphere, which were all published in Nature Astronomy. 

The measurements revealed that Voyager 2 encountered a thinner heliosphere boundary while Voyager 1 might have crossed during the solar maximum or may have crossed in a less perpendicular trajectory. 

Through a press release, Bill Kurth, a research scientist from the University of Iowa and co-author of the study, explains: "It implies that the heliosphere is symmetric, at least at the two points where the Voyager spacecraft crossed, and this states that these two points on the surface are almost at the same distance."

Voyager 2 was also able to measure the thickness of the outermost part of the heliosphere called the heliosheath. The heliosheath is the point where solar winds pile up and go against the incoming interstellar wind. 

These additional data sent back by Voyager fuel debate on the actual overall shape of the heliosphere. Spherical models were developed by some researchers to illustrate the activity in these regions while other scientists believe that the heliosphere's shape is similar to a windsock or a long tail floating behind as the solar system moving its way through the galaxy. 

However, the data that consist of measurement brought back by Voyager 2 seem to support the spherical model due to the magnetic fields outside and inside the heliosphere.

THE VOYAGER

Voyager 2 was launched by the National Aeronautics and Space Administration back in 1977 together with its twin spacecraft Voyager 1 as parts of the Voyager program designed to study the outer planets of the solar system. 

Considered as the longest-running space mission, Voyager 2 had successfully crossed the frontier in 2017, 40 years after its launch. Although launched 16 days prior to the launch of Voyager 1, the spacecraft was able to cross the threshold six years later than its twin and was able to take close photographs of Uranus and Neptune.