Posted: Wed, May 25, 2005, 5:33 AM ET (0933 GMT)
Space scientists said Tuesday that NASA's Voyager 1 spacecraft has reached the frontier of the solar system, a turbulent boundary between interplanetary and interstellar space. Speaking at an American Geophysical Union meeting in New Orleans, project scientists said that the magnetic field in the vicinity of the spacecraft suddenly increased by a factor of 2.5 last December and has remained at that high level since then. Scientists infer that the increase in magnetic field strength is caused by a decrease in the speed of the solar wind, evidence that the spacecraft has crossed a boundary called the "termination shock" where the outbound solar wind is slowed by pressure from the interstellar medium. Scientists had seen evidence as early as November 2003 that Voyager 1 was approaching or had entered the termination shock, but these results are the most convincing evidence to date that the spacecraft, launched in 1977 on a mission to the outer solar system, has in fact reached the solar system's boundary. The future of Voyager 1 and its twin, Voyager 2, remains in doubt as NASA considers cutting funding for continued operation of the spacecraft to help pay for other projects.
