Editing Voyager 2 (section)

=== Encounter with Neptune ===
{{Further|Exploration of Neptune}}

Following a course correction in 1987, ''Voyager 2''{{'}}s closest approach to Neptune occurred on August 25, 1989.<ref>{{cite news |title=Voyager Steered Toward Neptune |url=https://www.newspapers.com/image/555835 |access-date=December 6, 2017 |work=Ukiah Daily Journal |date=March 15, 1987 |archive-date=December 7, 2017 |archive-url=https://web.archive.org/web/20171207085743/http://www.newspapers.com/image/555835/ |url-status=live }}</ref><ref name="nasajpl"/> Through repeated computerized test simulations of trajectories through the Neptunian system conducted in advance, flight controllers determined the best way to route ''Voyager&nbsp;2'' through the Neptune–Triton system. Since the plane of the orbit of Triton is tilted significantly with respect to the plane of the ecliptic; through course corrections, ''Voyager&nbsp;2'' was directed into a path about {{Convert|4950|km|mi|abbr=unit}} above the north pole of Neptune.<ref name="national aeronautics and space administration-2" /><ref>{{cite web |title=Neptune |url=https://voyager.jpl.nasa.gov/science/neptune.html |publisher=Jet Propulsion Laboratory |access-date=March 3, 2016 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304090349/http://voyager.jpl.nasa.gov/science/neptune.html |url-status=live }}</ref> Five hours after ''Voyager 2'' made its closest approach to Neptune, it performed a close fly-by of [[Triton (moon)|Triton]], Neptune's largest moon, passing within about {{Convert|40000|km|mi|abbr=unit}}.<ref name="national aeronautics and space administration-2">[[National Aeronautics and Space Administration]] [https://voyager.jpl.nasa.gov/mission/science/neptune/ "Neptune Approach"] {{Webarchive|url=https://web.archive.org/web/20180909173736/https://voyager.jpl.nasa.gov/mission/science/neptune/ |date=September 9, 2018 }} NASA Jet Propulsion Laboratory: California Institute of Technology. Accessed December 12, 2018.</ref>

In 1989, the ''Voyager 2'' Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7×10{{sup|8}}&nbsp;J.<ref>{{cite journal |last1=Borucki |first1=W.J. |title=Predictions of lightning activity at Neptune |journal=Geophysical Research Letters |date=1989 |volume=16 |issue=8 |page=937-939 |doi=10.1029/gl016i008p00937|bibcode=1989GeoRL..16..937B }}</ref> A plasma wave system (PWS) detected 16 electromagnetic wave events with a frequency range of 50&nbsp;Hz&nbsp;– 12&nbsp;kHz at magnetic latitudes 7˚–33˚.<ref name="aplin-2020" /><ref name="gurnett-1990">{{cite journal |title=Whistlers in Neptune's magnetosphere: Evidence of atmospheric lightning |journal=Journal of Geophysical Research: Space Physics |date=1990 |volume=95 |page=20967-20976 |doi=10.1029/ja095ia12p20967|bibcode=1990JGR....9520967G |hdl=2060/19910002329 |hdl-access=free |last1=Gurnett |first1=D. A. |last2=Kurth |first2=W. S. |last3=Cairns |first3=I. H. |last4=Granroth |first4=L. J. |issue=A12 }}</ref> These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere.<ref name="gurnett-1990" /> During ''Voyager 2''{{'}}s closest approach to Neptune, the PWS instrument provided Neptune’s first plasma wave detections at a sample rate of 28,800 samples per second.<ref name="gurnett-1990" /> The measured plasma densities range from 10{{sup|–3}} – 10{{sup|–1}} cm{{sup|–3}}.<ref name="gurnett-1990" /><ref>{{cite journal |last1=Belcher |first1=J.W. |last2=Bridge |first2=H.S. |last3=Bagenal |first3=F. |last4=Coppi |first4=B. |last5=Divers |first5=O. |last6=Eviatar |first6=A. |last7=Gordon |first7=G.S. |last8=Lazarus |first8=A.J. |last9=McNutt |first9=R.L. |last10=Ogilvie |first10= K.W. |last11=Richardson |first11= J.D. |last12= Siscoe |first12=G.L. |last13=Sittler |first13=E.C. |last14=Steinberg |first14=J.T. |last15=Sullivan |first15=J.D. |last16=Szabo |first16=A. |last17=Villanueva |first17=L. |last18=Vasyliunas |first18=V.M. |last19=Zhang |first19=M. |title= Plasma observations near Neptune: Initial results from Voyager 2 |journal=Science |date=1989 |volume=246 |issue=4936 |pages=1478–1483 |doi=10.1126/science.246.4936.1478 |pmid=17756003 |bibcode=1989Sci...246.1478B }}</ref>

''Voyager 2'' discovered previously unknown [[Rings of Neptune|Neptunian rings]],<ref>[[National Aeronautics and Space Administration]] [https://solarsystem.nasa.gov/moons/neptune-moons/in-depth/ "Neptune Moons"] {{Webarchive|url=https://web.archive.org/web/20200410070225/https://solarsystem.nasa.gov/moons/neptune-moons/in-depth/ |date=April 10, 2020 }} NASA Science: Solar System Exploration. Updated December 6, 2017. Accessed December 12, 2018.</ref> and confirmed six new moons: [[Despina (moon)|Despina]], [[Galatea (moon)|Galatea]], [[Larissa (moon)|Larissa]], [[Proteus (moon)|Proteus]], [[Naiad (moon)|Naiad]] and [[Thalassa (moon)|Thalassa]].<ref name="elizabeth howell">Elizabeth Howell (2016) [https://www.space.com/22222-neptunes-moons.html "Neptune's Moons: 14 Discovered So Far"] {{Webarchive|url=https://web.archive.org/web/20181215172111/https://www.space.com/22222-neptunes-moons.html |date=December 15, 2018 }} ''[[Space.com]]'', June 30, 2016. Accessed December 12, 2018.</ref>{{efn-ua|One of these moons, [[Larissa (moon)|Larissa]], was first reported in 1981 from ground telescope observations, but not confirmed until the ''Voyager 2'' approach.<ref name="elizabeth howell" />}} While in the neighborhood of Neptune, ''Voyager 2'' discovered the "[[Great Dark Spot]]", which has since disappeared, according to observations by the [[Hubble Space Telescope]].<ref>Phil Plait (2016) [https://slate.com/technology/2016/06/hubble-observation-reveals-a-new-dark-spot-on-neptune.html "Neptune Just Got a Little Dark"] {{Webarchive|url=https://web.archive.org/web/20181215175353/https://slate.com/technology/2016/06/hubble-observation-reveals-a-new-dark-spot-on-neptune.html |date=December 15, 2018 }} ''[[Slate (magazine)|Slate]]'', June 24, 2016. Accessed December 12, 2018.</ref> The Great Dark Spot was later hypothesized to be a region of clear gas, forming a window in the planet's high-altitude methane cloud deck.<ref>[[National Aeronautics and Space Administration]] (1998) [https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA01286 "Hubble Finds New Dark Spot on Neptune"] {{Webarchive|url=https://web.archive.org/web/20170611173537/https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA01286 |date=June 11, 2017 }} NASA Jet Propulsion Laboratory: California Institute of Technology, August 2, 1998. Accessed December 12, 2018.</ref>

{{Gallery| align = center
| style="width:175px;"|File:Neptune Voyager2 color calibrated.png|alt1=''Voyager 2'' image of Neptune | ''Voyager 2'' image of [[Neptune]]
|File:Voyager 2 Neptune and Triton.jpg|alt2=Neptune and Triton three days after Voyager's flyby | [[Neptune]] and [[Triton (moon)|Triton]] three days after ''Voyager 2'' flyby
|File:Neptune clouds.jpg|alt7=Cirrus clouds imaged above gaseous Neptune | [[Cirrus clouds]] imaged above gaseous [[Neptune]]
|File:Rings of Neptune PIA01997.png|alt8=Rings of Neptune taken in occultation from 280,000&nbsp;km | [[Rings of Neptune]] taken in [[occultation]] from 280,000&nbsp;km
|File:Triton moon mosaic Voyager 2 (large).jpg|alt6=Color mosaic of ''Voyager 2'' Triton | Color mosaic of ''Voyager 2'' [[Triton (moon)|Triton]]
}}