page_title: Voyager 1
section_title: Interstellar medium
hierarchical_section_title: Voyager 1 / Interstellar medium
caption_attribution_description: English: Spacecraft that are on trajectories to leave the Solar System.
context_page_description: Voyager 1 is a space probe that was launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 was launched 16 days after its twin, Voyager 2. Having operated for 42 years, 11 months and 25 days as of August 30, 2020, the spacecraft still communicates with the Deep Space Network to receive routine commands and to transmit data to Earth. Real-time distance and velocity data is provided by NASA and JPL. At a distance of 149.39 AU from Earth as of July 26, 2020, it is the most distant man-made object from Earth.
  The probe's objectives included flybys of Jupiter, Saturn, and Saturn's largest moon, Titan. Although the spacecraft's course could have been altered to include a Pluto encounter by forgoing the Titan flyby, exploration of the moon took priority because it was known to have a substantial atmosphere. Voyager 1 studied the weather, magnetic fields, and rings of the two planets and was the first probe to provide detailed images of their moons.
context_section_description: On September 12, 2013, NASA officially confirmed that Voyager 1 had reached the interstellar medium in August 2012 as previously observed, with a generally accepted date of August 25, 2012 (approximately 10 days before the 35th anniversary of its launch), the date durable changes in the density of energetic particles were first detected. By this point most space scientists had abandoned the hypothesis that a change in magnetic field direction must accompany crossing of the heliopause; a new model of the heliopause predicted that no such change would be found. A key finding that persuaded many scientists that the heliopause had been crossed was an indirect measurement of an 80-fold increase in electron density, based on the frequency of plasma oscillations observed beginning on April 9, 2013, triggered by a solar outburst that had occurred in March 2012 (electron density is expected to be two orders of magnitude higher outside the heliopause than within). Weaker sets of oscillations measured in October and November 2012 provided additional data. An indirect measurement was required because Voyager 1's plasma spectrometer had stopped working in 1980. In September 2013, NASA released recordings of audio transductions of these plasma waves, the first to be measured in interstellar space.
  While Voyager 1 is commonly spoken of as having left the Solar System simultaneously with having left the heliosphere, the two are not the same. The Solar System is usually defined as the vastly larger region of space populated by bodies that orbit the Sun. The craft is presently less than one-seventh the distance to the aphelion of Sedna, and it has not yet entered the Oort cloud, the source region of long-period comets, regarded by astronomers as the outermost zone of the Solar System.
caption: Voyager 1 and the other probes that are in or on their way to interstellar space, except New Horizons.
exif: {}