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NASA's Voyager 2 spacecraft has detected an increase in cosmic rays from the solar system. The probe is currently about 17.7 billion kilometers from Earth.
This image shows the position of NASA's Voyager 1 and Voyager 2 probes, relative to the heliosphere. Image credit: NASA / JPL-Caltech.
Voyager 2 was launched on August 20, 1977 from the NASA Kennedy Space Center in Cape Canaveral, Florida, and was propelled into space aboard a Titan / Centaur rocket.
The initial mission plan for the spacecraft specified visits only to Jupiter and Saturn. The plan was strengthened in 1981 to include a visit to Uranus, and again in 1985 to include an overview of Neptune.
Since 2007, Voyager 2 traverses the outermost layer of the heliosphere, a comet-like bubble around the solar system dominated by solar material and magnetic fields.
NASA scientists are monitoring the presence of the probe in the outer limit of the heliosphere, the heliopause.
Once Voyager 2 has left the heliosphere, it will become the second human-made object, after Voyager 1, to enter the interstellar medium.
Since August 2018, the Voyager 2 Cosmic Ray Subsystem subsystem instrument has measured an increase of approximately 5% in the cosmic ray rate reaching the spacecraft. Its low-energy charged particle instrument has detected a similar increase in high-energy cosmic rays.
"Cosmic rays are fast-moving particles that come from the solar system," NASA researchers said.
"Some of these cosmic rays are blocked by the heliosphere, so we expect Voyager 2 to measure an increase in the rate of cosmic rays as it approaches and crosses the boundaries of the heliosphere. . "
In May 2012, Voyager 1 experienced an increase in the cosmic ray rate similar to that detected by Voyager 2.
It was about three months before Voyager 1 passed through the heliopause and entered the interstellar medium.
"However, the increase in cosmic rays is not a definite sign that the probe is about to pass through the heliopause," the scientists said.
"Voyager 2 is at a different location than Voyager 1 in the heliosheath – the outer region of the heliosphere – and the possible differences at these locations mean that Voyager 2 might experience a different exit schedule from Traveling 1. "
"We are seeing a change in the environment around Voyager 2, there is no doubt about it," said Ed Stone, a researcher at Voyager, a researcher at Caltech.
"We will learn a lot in the months to come, but we still do not know when we will hit the heliopause. We are not there yet. It's something I can say with confidence. "
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