NASA’s Voyager 2 reveals mysteries of interstellar space as it travels beyond solar system

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VOYAGER 2 has just sent back its first message after breaking through the heliosphere “bubble” that surrounds our solar system and crossing into the mysteries of interstellar space.

The NASA probe has sent back data of what is out there beyond, beyond the solar system’s edge. Professor Ed Stone, of the California Institute of Technology, who has been working on the mission since before its launch in 1977, said: “We didn’t know how large the bubble was and we certainly didn’t know that the spacecraft could live long enough to reach the edge of the bubble and enter interstellar space.” The information sent back gives some insight into the shape of the heliosphere, tracing out a leading edge something like a blunt bullet.

Bill Kurth, a University of Iowa research scientist and a co-author on one of the studies, said: “It implies that the heliosphere is symmetric, at least at the two points where the Voyager spacecraft crossed,”

Mr Kurth added: “That says that these two points on the surface are almost at the same distance.”

Measurements published in five separate papers in Nature Astronomy reveal that Voyager 2 encountered a much sharper, thinner heliosphere boundary than Voyager 1.

This could be due to Voyager 1 crossing during a solar maximum, as presently solar activity is currently at a low, or the craft itself might have crossed through on a less perpendicular trajectory that meant it ended up spending longer at the edge.

It was once thought that the solar wind faded away gradually with distance, but Voyager 1 confirmed there was a boundary, defined by a sudden drop in temperature and an increase in the density of charged particles, known as plasma.

The heliosphere is twelve billion miles from Earth.

It is an elusive boundary that marks the edge of the sun’s realm and the start of interstellar space.

The heliosphere is a bubble-like region of space which surrounds and is created by the Sun.

In plasma physics terms, this is the cavity formed by the Sun in the surrounding interstellar medium.

The “bubble” of the heliosphere is continuously “inflated” by plasma originating from the Sun, known as the solar wind.

Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating our galaxy.

Radiation levels inside and outside the heliosphere differ; in particular, the galactic cosmic rays are less abundant inside the heliosphere, so that the planets inside (including Earth) are partly shielded from their impact.


The word “heliosphere” is said to have been coined by Alexander J. Dessler, who is credited with first use of the word in scientific literature in 1967.

The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.

Voyager 2 is now in its extended mission to study the outer reaches of the Solar System and has been operating for 42 years, 2 months and 15 days as of November 4, 2019. It remains in contact through the NASA Deep Space Network.

The Voyager 2 probe was launched on August 20, 1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida, aboard a Titan IIIE/Centaur launch vehicle.

Two weeks later, the twin Voyager 1 probe was launched on September 5, 1977.

However, Voyager 1 reached both Jupiter and Saturn sooner, as Voyager 2 had been launched into a longer, more circular trajectory.

Voyager 2 is equipped with 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG).

Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch.

Collectively, the power unit within the spacecraft will allow operations to continue until at least 2020.

It uses 24 pressed plutonium-238 oxide spheres and provides enough heat to generate approximately 157 watts of electrical power initially, halving every 87.7 years.

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