Voyager 1 and Voyager 2 launched a few weeks apart in 1977, tasked with performing unprecedented “grand tour” of the solar system’s giant planets. Voyager 1 flew by Jupiter and Saturn; Voyager 2 did the same but then zoomed past Uranus and Neptune as well.
Voyager 1 continues to collect information in the coming years, Voyager 2 will also pass beyond the Solar System. Because it’s leaving at a different angle to its twin. The data Voyager 2 gathers will give scientists an insight into the shape of the solar bubble.
Voyager 2 traversed the heliopause, the boundary between the heliosphere and interstellar space. When the probe was 119 astronomical units (AU) from the sun. (One AU is the average Earth-sun distance, which is about 93 million miles, or 150 million kilometers.) Voyager 1 made the crossing at nearly the same distance, 121.6 AU.
Voyager 2’s measurements of the interstellar magnetic field are also intriguing. Before Voyager 1’s 2012 crossing, the team expected to see significant differences in the direction of the magnetic field outside the heliosphere. It is compared with the single inside, said Leonard Burlaga of NASA’s Goddard Space Flight Center in Maryland.
Voyager 2 measured relatively high solar-wind speeds almost all the way through until crossing. And Voyager 2’s data suggest a smoother and thinner heliopause than that observed by Voyager 1 (though both spacecraft apparently traversed the boundary in less than a day).
The newly detected electron bursts are like an advanced guard accelerated along magnetic field lines in the interstellar medium. The electrons travel at nearly the speed of light, some 670 times faster than shock waves that initially propelled them. The bursts were followed by plasma wave oscillations caused by lower-energy electrons.
The discovery could help physicists better understand the dynamics underpinning shock waves. And also cosmic radiation that come from flare stars (which can vary in brightness briefly due to violent activity on their surface) and exploding stars.
The Voyagers continue teaching scientists more about the region to this day. And they have informed subsequent missions of exploration, explained Linda Spilker, deputy project scientist for Voyager and former project scientist for the Cassini mission to Saturn.
As well as finding new rings and identifying an additional moon, the Voyager spacecraft investigated the moon of Titan with its thick petrochemical atmosphere and methane rain. It also sent back close-up images of the moon Enceladus. This tiny, ice-encased world, around the size of the UK, is the most reflective body in the Solar System. Both moons have subsequently been investigated by the Cassini-Huygens mission, with Enceladus now ranked as a prime candidate for life.
“Data from the Voyager 2 Saturn flyby provided key information for the development of instruments. And science goals for the Cassini orbiter mission that circled Saturn for 13 years, starting in 2004,” she said. “Voyager 2 data, in conjunction with Cassini data, provided a multi-decade temporal view of Saturn, rings and Titan.”
The “leakage” observed by both spacecraft. Voyager 1 detected interstellar particles on two separate occasions as it neared the heliopause. And the mission team has attributed that finding to two intruding “interstellar flux tubes”. But Voyager 2’s experience was quite the opposite. The probe detected some solar particles for a while after it left the heliosphere.
Voyager 1 and Voyager 2 spacecraft, occurred as the Voyagers continue their journey outward through interstellar space, thus making them the first craft to record this unique physics in the realm between stars.
In the coming 5 to 10 years, the spacecraft will continue sending back data on how far into the interstellar medium the Sun’s influence extents. How changes in the solar cycle affect the physics of the very local interstellar medium. And how particles and fields in the very local interstellar medium change in relation to distance from the Sun, she said.
But the Voyagers are nearing the end of the line. Each spacecraft is powered by three radioisotope thermoelectric generators (RTGs), which convert to electricity the heat generated by the radioactive decay of plutonium-238. The RTGs’ power output decreases over time as more and more of the plutonium decays.