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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Voyager 1 | 4/7 | https://en.wikipedia.org/wiki/Voyager_1 | reference | science, encyclopedia | 2026-05-05T13:27:04.653048+00:00 | kb-cron |
==== Heliosheath ==== On March 31, 2006, amateur radio operators from AMSAT in Germany tracked and received radio waves from Voyager 1 using the 20-meter (66 ft) dish at Bochum with a long integration technique. Retrieved data was checked and verified against data from the Deep Space Network station at Madrid, Spain. This seems to be the first such amateur tracking of Voyager 1. It was confirmed on December 13, 2010, that Voyager 1 had passed the reach of the radial outward flow of the solar wind, as measured by the Low Energy Charged Particle device. It is suspected that solar wind at this distance turns sideways because of interstellar wind pushing against the heliosphere. Since June 2010, detection of solar wind had been consistently at zero, providing conclusive evidence of the event. On this date, the spacecraft was approximately 116 AU (17.4 billion km; 10.8 billion mi) from the Sun. Voyager 1 was commanded to change its orientation to measure the sideways motion of the solar wind at that location in space in March 2011 (~33 years 6 months from launch). A test roll in February had confirmed the spacecraft's ability to maneuver and reorient itself. The course of the spacecraft was not changed. It rotated 70 degrees counterclockwise with respect to Earth to detect the solar wind. This was the first time the spacecraft had done any major maneuvering since the Family Portrait photograph of the planets was taken in 1990. After the first roll the spacecraft had no problem in reorienting itself with Alpha Centauri, Voyager 1's guide star, and it resumed sending transmissions back to Earth. Voyager 1 was expected to enter interstellar space "at any time". Voyager 2 was still detecting outward flow of solar wind at that point but it was estimated that in the following months or years it would experience the same conditions as Voyager 1. The spacecraft was reported at 12.44° declination and 17.163 hours right ascension, and at an ecliptic latitude of 34.9° (the ecliptic latitude changes very slowly), placing it in the constellation Ophiuchus as observed from the Earth on May 21, 2011. On December 1, 2011, it was announced that Voyager 1 had detected the first Lyman-alpha radiation originating from the Milky Way galaxy. Lyman-alpha radiation had previously been detected from other galaxies, but because of interference from the Sun, the radiation from the Milky Way was not detectable. NASA announced on December 5, 2011, that Voyager 1 had entered a new region referred to as a "cosmic purgatory". Within this stagnation region, charged particles streaming from the Sun slow and turn inward, and the Solar System's magnetic field is doubled in strength as interstellar space appears to be applying pressure. Energetic particles originating in the Solar System decline by nearly half, while the detection of high-energy electrons from outside increases 100-fold. The inner edge of the stagnation region is located approximately 113 AU from the Sun.
==== Heliopause ==== NASA announced in June 2012 that the probe was detecting changes in the environment that were suspected to correlate with arrival at the heliopause. Voyager 1 had reported a marked increase in its detection of charged particles from interstellar space, which are normally deflected by the solar winds within the heliosphere from the Sun. The craft thus began to enter the interstellar medium at the edge of the Solar System. Voyager 1 became the first spacecraft to cross the heliopause in August 2012, then at a distance of 121 AU (1.12×1010 mi; 1.81×1010 km) from the Sun, although this was not confirmed for another year. As of September 2012, sunlight took 16.89 hours to reach Voyager 1, which was at a distance of 121 AU. The apparent magnitude of the Sun from the spacecraft was −16.3 (about 30 times brighter than the full Moon). The spacecraft was traveling at 17.043 km/s (10.590 mi/s) relative to the Sun. At this rate, it would need about 17,565 years to travel a single light-year. To compare, Proxima Centauri, the closest star to the Sun, is about 4.2 light-years (2.65×105 AU) distant. If the spacecraft was traveling in the direction of that star, it would take 73,775 years to reach it. Voyager 1 is heading in the direction of the constellation Ophiuchus. In late 2012, researchers reported that particle data from the spacecraft suggested that the probe had passed through the heliopause. Measurements from the spacecraft revealed a steady rise since May in collisions with high energy particles (above 70 MeV), which are thought to be cosmic rays emanating from supernova explosions far beyond the Solar System, with a sharp increase in these collisions in late August. At the same time, in late August, there was a dramatic drop in collisions with low-energy particles, which are thought to originate from the Sun. Ed Roelof, a space scientist at Johns Hopkins University and principal investigator for the Low-Energy Charged Particle instrument on the spacecraft, declared that "most scientists involved with Voyager 1 would agree that [these two criteria] have been sufficiently satisfied". However, the last criterion for officially declaring that Voyager 1 had crossed the boundary, the expected change in magnetic field direction (from that of the Sun to that of the interstellar field beyond), had not been observed (the field had changed direction by only 2 degrees), which suggested to some that the nature of the edge of the heliosphere had been misjudged. On December 3, 2012, Voyager project scientist Ed Stone of the California Institute of Technology said, "Voyager has discovered a new region of the heliosphere that we had not realized was there. We're still inside, apparently. But the magnetic field now is connected to the outside. So it's like a highway letting particles in and out." The magnetic field in this region was 10 times more intense than Voyager 1 encountered before the termination shock. It was expected to be the last barrier before the spacecraft exited the Solar System completely and entered interstellar space.