An increase in cosmic rays originating outside our solar system has been detected by NASA’s Voyager 2 probe, which is presently on a journey toward interstellar space.
Voyager 2 was deployed in 1977 and is currently just under 11 billion miles (about 17.7 billion kilometres) from Earth or more than 118 times the distance from Earth to the Sun.
Ever since 2007, the probe has been flying through the outermost layer of the heliosphere, which is the massive bubble around the Sun and the planets controlled by solar material and magnetic fields.
The scientists behind Voyager have been watching for the spacecraft to reach the outer boundary of the heliosphere, called the heliopause. Once Voyager 2 exits the heliosphere, it will become the second man made object, after Voyager 1, to enter interstellar space.
Of course, as Asgardia works towards setting up habitable platforms in space, spacecraft that can journey through space are important to follow.
What’s more, for the past two months the Cosmic Ray Subsystem instrument on Voyager 2 has measured approximately a 5 percent increase in the rate of cosmic rays hitting the spacecraft in comparison to early August. The probe’s Low-Energy Charged Particle instrument has identified a similar rise in higher-energy cosmic rays.
Cosmic rays are fast-moving particles that are born outside our solar system. The heliosphere blocks some of these cosmic rays, so mission planners anticipate that Voyager 2 will measure an increase in the rate of cosmic rays as it nears and crosses the boundary of the heliosphere.
What’s more, in May 2012, Voyager 1 detected an increase in the rate of cosmic rays much like what Voyager 2 is now picking up. That was around three months before Voyager 1 crossed the heliopause and entered interstellar space.
But, Voyager team members state that the increase in cosmic rays is not proof that the probe is about to cross the heliopause. Voyager 2 is in a different location in the heliosheath — the outer region of the heliosphere — than Voyager 1 had been, and possible differences in these regions mean Voyager 2 could experience a different exit timeline than Voyager 1.
It is relevant that Voyager 2 could be approaching the heliopause six years after Voyager 1 since the heliopause moves inward and outward during the Sun’s 11-year activity cycle. Solar activity deals with emissions from the Sun, such as solar flares and eruptions of material known as coronal mass ejections. During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of this activity.
Voyager Project Scientist Ed Stone, based at Caltech in Pasadena explained that experts are seeing a change in the environment around Voyager 2, which means they will learn a lot in the coming months. However, they still don’t know when Voyager 2 will reach the heliopause.
NASA’s Jet Propulsion Laboratory in Pasadena, California, built the Voyager spacecraft and they continue to operate both. JPL is a division of Caltech. The Voyager missions are a part of the NASA Heliophysics System Observatory, managed by the Heliophysics Division of the Science Mission Directorate in Washington.