Space

NASA Voyager 2 Nearing Interstellar Space, Measures Increase in Cosmic Rays

Voyager 2 Nearing Interstellar Space

This graphic shows the position of the Voyager 1 and Voyager 2 probes relative to the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Voyager 1 crossed the heliopause, or the edge of the heliosphere, in 2012. Voyager 2 is still in the heliosheath, or the outermost part of the heliosphere. Credit: NASA/JPL-Caltech

NASA’s Voyager 2 probe, currently on a journey toward interstellar space, has detected an increase in cosmic rays that originate outside our solar system. Launched in 1977, Voyager 2 is a little less than 11 billion miles (about 17.7 billion kilometers) from Earth, or more than 118 times the distance from Earth to the Sun.

Since 2007 the probe has been traveling through the outermost layer of the heliosphere — the vast bubble around the Sun and the planets dominated by solar material and magnetic fields. Voyager scientists have been watching for the spacecraft to reach the outer boundary of the heliosphere, known as the heliopause. Once Voyager 2 exits the heliosphere, it will become the second human-made object, after Voyager 1, to enter interstellar space.

Since late August, the Cosmic Ray Subsystem instrument on Voyager 2 has measured about a 5 percent increase in the rate of cosmic rays hitting the spacecraft compared to early August. The probe’s Low-Energy Charged Particle instrument has detected a similar increase in higher-energy cosmic rays.

Cosmic rays are fast-moving particles that originate outside the solar system. Some of these cosmic rays are blocked by the heliosphere, so mission planners expect that Voyager 2 will measure an increase in the rate of cosmic rays as it approaches and crosses the boundary of the heliosphere.

In May 2012, Voyager 1 experienced an increase in the rate of cosmic rays similar to what Voyager 2 is now detecting. That was about three months before Voyager 1 crossed the heliopause and entered interstellar space.

However, Voyager team members note that the increase in cosmic rays is not a definitive sign 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 locations means Voyager 2 may experience a different exit timeline than Voyager 1.

The fact that Voyager 2 may be approaching the heliopause six years after Voyager 1 is also relevant, because the heliopause moves inward and outward during the Sun’s 11-year activity cycle. Solar activity refers to emissions from the Sun, including solar flares and eruptions of material called coronal mass ejections. During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of activity.

“We’re seeing a change in the environment around Voyager 2, there’s no doubt about that,” said Voyager Project Scientist Ed Stone, based at Caltech in Pasadena. “We’re going to learn a lot in the coming months, but we still don’t know when we’ll reach the heliopause. We’re not there yet — that’s one thing I can say with confidence.”

The Voyager spacecraft were built by NASA’s Jet Propulsion Laboratory in Pasadena, California, which continues 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.

Share

View Comments

By
Calla Cofield / Jia-Rui Cook, Jet Propulsion Laboratory

Recent Posts

Explosive Neutron Star Merger Captured in Millimeter Light for the First Time

The flash is one of the most energetic short-duration gamma-ray bursts ever observed. For the…

October 3, 2022

New Method Converts Fish Waste Into Valuable Nanomaterial in Seconds

Researchers create a simple, quick, and energy-efficient approach for synthesizing quality carbon nano-onions from fish scales.…

October 3, 2022

Scientists Find That Men Have a High Probability of Outliving Women

Large disparities in life expectancy may often obscure significant overlap in lifespan. A statistical analysis…

October 3, 2022

Incredible Telescope View Captures DART Asteroid Impact

On Monday, September 26, 2022, at 7:14 p.m. EDT (23:14 UTC), NASA's DART spacecraft successfully…

October 3, 2022

New Air Filter Features Excellent Performance and Endurance in Harsh Environments

New air filter design promises strong potential for applications in automobiles and industry. A high-performance…

October 3, 2022

Advancing Structural Biology With Novel Cell-Free Protein Crystallization Method

Tokyo Tech developed a new cell-free protein crystallization (CFPC) method that includes direct protein crystallization…

October 3, 2022