Editing Voyager 1 (section)

=== 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 (astronomy)|heliopause]].<ref>{{Cite web |date=June 18, 2012 |title=NASA Voyager 1 Spacecraft Nears Interstellar Space |url=https://www.space.com/16167-voyager1-spacecraft-interstellar-space.html |url-status=live |archive-url=https://web.archive.org/web/20130705080432/http://www.space.com/16167-voyager1-spacecraft-interstellar-space.html |archive-date=July 5, 2013 |access-date=August 19, 2013 |publisher=Space.com}}</ref> ''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.<ref>{{Cite web |date=June 14, 2012 |title=Data From NASA's Voyager 1 Point to Interstellar Future |url=https://www.nasa.gov/mission_pages/voyager/voyager20120614.html |url-status=live |archive-url=https://web.archive.org/web/20120617040828/http://www.nasa.gov/mission_pages/voyager/voyager20120614.html |archive-date=June 17, 2012 |access-date=June 16, 2012 |publisher=[[NASA]]}}</ref>

''Voyager 1'' became the first spacecraft to cross the heliopause in August 2012, then at a distance of {{Convert|121|AU|mi km|abbr=unit}} from the Sun, although this was not confirmed for another year.<ref name="cook-2013a">{{Cite web |last1=Cook |first1=J.-R.C. |last2=Agle |first2=D.C. |last3=Brown |first3=D. |date=September 12, 2013 |title=NASA Spacecraft Embarks on Historic Journey into Interstellar Space |url=https://www.nasa.gov/mission_pages/voyager/voyager20130912.html |url-status=live |archive-url=https://web.archive.org/web/20200413080742/http://www.nasa.gov/mission_pages/voyager/voyager20130912.html |archive-date=April 13, 2020 |access-date=September 14, 2013 |website=NASA}}</ref><ref name="ghose-2013" /><ref name="cowen-2013" /><ref name="kerr-2013" /><ref name="gurnett-2013" />

As of September 2012, sunlight took 16.89 hours to get to ''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).<ref name="peat-2012">{{Cite web |last=Peat |first=Chris |date=September 9, 2012 |title=Spacecraft escaping the Solar System |url=https://www.heavens-above.com/SolarEscape.aspx |url-status=live |archive-url=https://web.archive.org/web/20180511013456/http://www.heavens-above.com/SolarEscape.aspx |archive-date=May 11, 2018 |access-date=March 16, 2014 |publisher=[[Heavens-Above]]}}</ref> The spacecraft was traveling at {{Convert|17.043|km/s|mi/s|abbr=on}} relative to the Sun. At this rate, it would need about 17,565 years to travel a single [[light-year]].<ref name="peat-2012" /> To compare, [[Proxima Centauri]], the closest star to the Sun, is about 4.2 light-years ({{val|2.65|e=5|u=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 (constellation)|Ophiuchus]].<ref name="peat-2012" />

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 ray]]s 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.<ref name="wolchover-2012">{{Cite web |last=Wolchover |first=Natalie |date=October 9, 2012 |title=Did NASA's Voyager 1 Spacecraft Just Exit the Solar System? |url=https://www.livescience.com/23822-voyager-spacecraft-solar-system.html |url-status=live |archive-url=https://web.archive.org/web/20131003054345/http://www.livescience.com/23822-voyager-spacecraft-solar-system.html |archive-date=October 3, 2013 |access-date=August 20, 2013 |publisher=livescience}}</ref>

Ed Roelof, 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".<ref name="wolchover-2012" /> 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),<ref name="ghose-2013" /> 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."<ref>{{Cite magazine |last=Matson |first=John |date=December 4, 2012 |title=Despite Tantalizing Hints, Voyager 1 Has Not Crossed into the Interstellar Medium |url=https://blogs.scientificamerican.com/observations/2012/12/04/despite-tantalizing-hints-voyager-1-has-not-crossed-into-the-interstellar-medium/ |magazine=Scientific American |access-date=August 20, 2013 |archive-date=March 13, 2013 |archive-url=https://web.archive.org/web/20130313051418/http://blogs.scientificamerican.com/observations/2012/12/04/despite-tantalizing-hints-voyager-1-has-not-crossed-into-the-interstellar-medium/? |url-status=live }}</ref> 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.<ref>{{Cite web |date=December 3, 2012 |title=Voyager 1 Can 'Taste' the Interstellar Shore |url=http://news.discovery.com/space/voyager-1-flys-into-a-mystery-magnetic-highway-121203.html |url-status=dead |archive-url=https://web.archive.org/web/20121205081342/http://news.discovery.com/space/voyager-1-flys-into-a-mystery-magnetic-highway-121203.html |archive-date=December 5, 2012 |access-date=September 16, 2013 |website=Discovery News |publisher=Discovery Channel}}</ref><ref>{{Cite web |last=Oakes |first=Kelly |date=December 3, 2012 |title=Voyager 1 is still not out of the Solar System |url=https://blogs.scientificamerican.com/basic-space/2012/12/03/voyager-1-is-still-not-out-of-the-solar-system/ |url-status=live |archive-url=https://web.archive.org/web/20130310144859/http://blogs.scientificamerican.com/basic-space/2012/12/03/voyager-1-is-still-not-out-of-the-solar-system/ |archive-date=March 10, 2013 |access-date=September 16, 2013 |website=Basic Space Blog |publisher=Scientific American}}</ref><ref>{{Cite news |date=December 4, 2012 |title=Voyager 1 probe leaving Solar System reaches 'magnetic highway' exit |work=Daily News & Analysis |agency=Reuters |url=http://www.dnaindia.com/scitech/report_voyager-1-probe-leaving-solar-system-reaches-magnetic-highway-exit12-4-2012-8-04-28-am_1773168%7C |url-status=live |access-date=December 4, 2012 |archive-url=https://web.archive.org/web/20230813133221/https://www.dnaindia.com/technology/report_voyager-1-probe-leaving-solar-system-reaches-magnetic-highway-exit12-4-2012-8-04-28-am_1773168%7C |archive-date=August 13, 2023}}</ref>