November and there has been no sign of it since. The three other instruments on board measuring cosmic rays, low-energy charged particles, and magnetic fields also recorded the transition. The observations complement data from NASA's IBEX mission. NASA is also preparing an additional mission, Interstellar Mapping and Acceleration Probe (IMAP) which is due to launch in 2024 to capitalise on Voyager observations. Timeline of exploration and detection 1904: The Potsdam Great Refractor with a spectrograph detects interstellar medium. The binary star Mintaka in Orionis determined to have the element calcium in the intervening space. January 1959: Luna 1 becomes the first spacecraft to observe the solar wind. 1962: Mariner 2 detects the solar wind. 1972–1973: Pioneer 10 becomes the first spacecraft to explore the heliosphere past Mars, flying by Jupiter on 4 December 1973 and continuing to return solar wind data out to a distance of 67 AU. February 1992: After flying by Jupiter, the Ulysses spacecraft becomes the first to explore the mid and high latitudes of the heliosphere. 1992: Pioneer and Voyager probes detected Ly-α radiation resonantly scattered by heliospheric hydrogen. 2004: Voyager 1 becomes the first spacecraft to reach the termination shock. 2005: SOHO observations of the solar wind show that the shape of the heliosphere is not axisymmetrical, but distorted, very likely under the effect of the local galactic magnetic field. 2009: IBEX project scientists discover and map a ribbon-shaped region of intense energetic neutral atom emission. These neutral atoms are thought to be originating from the heliopause. October 2009: the heliosphere may be bubble, not comet shaped. October 2010: significant changes were detected in the ribbon after six months, based on the second set of IBEX observations. May 2012: IBEX data implies there is probably not a bow "shock". June 2012: At 119 AU, Voyager 1 detected an increase in cosmic rays. 25 August 2012: Voyager 1 crosses the heliopause, becoming the first human-made object to depart the heliosphere. August 2018: long-term studies about the hydrogen wall by the New Horizons spacecraft confirmed results first detected in 1992 by the two Voyager spacecraft. 5 November 2018: Voyager 2 crosses the heliopause, departing the heliosphere. See also Coronal mass ejection Fermi glow References Sources Further reading Universe Today this-is-what-the-solar-system-really-looks-like External links Voyager Interstellar Mission Objectives NASA GALEX (Galaxy evolution Explorer) homepage at Caltech A Big Surprise from the Edge of the Solar System (NASA 06.09.11) Articles