NASA’s Voyager 2 probe (Voyager 2), currently on its way to interstellar space, recorded an increase in the intensity of cosmic rays coming from outside the solar system. Launched into space in 1977, the Voyager 2 probe is located at a distance of just under 17.7 million kilometers from Earth, which is equivalent to 118 distances from Earth to the Sun.
Since 2007, the probe has moved through the outermost layer of the heliosphere – a huge “bubble” surrounding the Sun and planets, within which the solar material and magnetic fields dominate. The scientists at Voyager 2 expected to see signs that the spacecraft would reach the outer boundary of the heliosphere, called the heliopause. When the Voyager 2 goes beyond the heliosphere, it will become the second artificial object in the world, after Voyager 1, that has ever entered interstellar space.
In the second half of August, the onboard instrument of the Voyager 2 probe, called Cosmic Ray Subsystem, recorded a 5 percent increase in the intensity level of cosmic rays reaching the device, compared with the beginning of August. The Low-Energy Charged Particle probe tool registered a similar increase in the intensity of high-energy cosmic rays.
Cosmic rays are fast-moving particles from outside the solar system. Some of these cosmic rays are blocked by the heliosphere, so it is believed that a sharp increase in the intensity of cosmic rays should be observed on the border with interstellar space.
In May 2012, the Voyager 1 apparatus experienced a similar increase in the intensity of cosmic rays, and then, three months later, crossed the heliopause and entered into interstellar space. However, according to scientists, such a 5 percent increase in the intensity of cosmic rays is not an unambiguous sign of the output of the apparatus from the heliosphere. In fact, the Voyager 2 can leave the heliosphere much later. The large difference in the time of the intersection of the heliopause for two twin machines can be explained by different activity of the Sun and, accordingly, by different sizes of the heliosphere “bubble”, the scientists explained.