Posted: Sun, Dec 16, 2018, 12:35 PM ET (1735 GMT)

Voyager 2 has joined its twin spacecraft in interstellar space. NASA announced Monday that the 41-year-old spacecraft passed the heliopause, the boundary between the bubble of space dominated by the solar wind and the surrounding interstellar medium, last month. Voyager 1, on a different trajectory out of the solar system, crossed the heliopause in 2012. Voyager's project manager said at a briefing Monday that the two spacecraft remain in good health but face dwindling power as their nuclear power sources decay. The spacecraft may be able to continue operating for as long as a decade.