News brief: Voyager 2 has passed beyond the heliopause

At a press briefing at the American Geophysical Union meeting today, NASA announced that several instruments on Voyager 2 confirmed that it had passed beyond the solar system boundary known as the heliopause. Unlike Voyager 1, which spent several years flirting with this boundary, the signs were pretty clear on Voyager 2. It helps that Voyager 2’s Plasma Spectrometer (PLS) is functioning (Voyager 1’s failed in 1980). Voyager 2 passed the termination shock in 2007; its passage across the heliopause means that it is now sensing the interstellar medium and is beyond the reach of the solar wind. It is still well inside the solar system: the Voyagers will take a few hundred years to reach the Oort cloud, the birthplace of comets. I like Phil Metzger’s framing of this news: Voyager 2 “went outside the Sun.”

Project manager Suzanne Dodd said that Voyager 2 can keep functioning for 5 to 10 more years in this new region of space, though not with all its instruments operating. It is currently running at only 3.6 degrees Celsius, not much higher than the freezing point of hydrazine. Still, she’s set a personal goal of keeping at least one of the Voyagers going until 2027, making it a 50-year mission.

For more on this story:

• NASA press release: “NASA’s Voyager 2 Probe Enters Interstellar Space”
• NASA educational video: “NASA’s Voyager 2 Enters Interstellar Space”
• JPL article on the interstellar medium
• Ed Stone’s kitchen sink, a visual analogy for the termination shock, heliosheath, and heliopause
• Routinely updated data from the Voyager cosmic ray subsystem