Saturn timeline, from Babylon to Dragonfly
This Saturn timeline lists the key dates in the discovery and exploration of the ringed planet. The milestones are Galileo's first telescopic view in 1610, Huygens' discovery of Titan in 1655 and of the ring in 1659, Cassini's discovery of the division in 1675, the first spacecraft flyby by Pioneer 11 in 1979, the Cassini orbiter from 2004 to 2017 with the Huygens landing on Titan in 2005, and the count of 274 moons reached in March 2025. NASA's Dragonfly is the next planned step, with arrival at Titan in 2034.
Contents
Antiquity to the Renaissance
| Date | Event |
|---|---|
| 1st millennium BCE | Babylonian astronomers record Saturn's positions and its 59-year cycle of recurring appearances |
| c. 4th century BCE | Greek astronomers call the planet Phainon; it later becomes the star of Kronos, Saturn to the Romans |
| c. 150 CE | Ptolemy's Almagest models Saturn's motion; it is the outermost known planet |
| 1543 | Copernicus places Saturn in a Sun-centered system with a period of about 30 years |
Saturn's mythological background is explored in the mythology section.
The age of the telescope: 1610–1700
| Date | Event |
|---|---|
| July 1610 | Galileo sees Saturn as "triple": a central body with two companions |
| 1612 | The companions vanish as Earth crosses the ring plane |
| 1616 | Galileo draws them as "ears" or handles |
| 25 March 1655 | Christiaan Huygens discovers Titan |
| 1659 | Huygens' Systema Saturnium explains the ring |
| 1669 | Giovanni Domenico Cassini arrives in Paris to work at the new Observatory |
| October 1671 | Cassini discovers Iapetus |
| December 1672 | Cassini discovers Rhea |
| 1675 | Cassini observes the dark gap in the ring, now the Cassini Division |
| March 1684 | Cassini discovers Tethys and Dione |
The people behind these dates are profiled on Huygens and Cassini, the astronomers; the full story is on the history of observation page.
The physics of the rings: 1700–1966
| Date | Event |
|---|---|
| 1781 | Uranus is discovered; Saturn is no longer the most distant known planet |
| 1787 | Laplace shows that a wide solid ring would be unstable |
| August–September 1789 | William Herschel discovers Enceladus and Mimas |
| 1837 | Encke reports a dark band in the A ring (Encke Gap) |
| September 1848 | Hyperion is discovered by the Bonds and by Lassell |
| 1848–1849 | Édouard Roche defines the Roche limit |
| 1850 | The faint C ring is described |
| 1859 | Maxwell proves the rings must consist of countless particles |
| 1876 | A great white storm is recorded, the first of a series roughly every 30 years |
| 1895 | Keeler confirms by spectroscopy that the rings are made of particles |
| 1899 | Pickering discovers Phoebe on photographic plates |
| 1933 | A great white spot is seen by the amateur astronomer Will Hay |
| 1944 | Kuiper detects methane on Titan, the first moon known to have an atmosphere |
| December 1966 | Audouin Dollfus (France) discovers Janus; Richard Walker sees Epimetheus |
The spacecraft era: 1973–2017
| Date | Event |
|---|---|
| 6 April 1973 | Launch of Pioneer 11 |
| 1977 | Launch of Voyager 2 (20 August) and Voyager 1 (5 September) |
| 1 September 1979 | Pioneer 11 makes the first flyby; discovery of the F ring |
| 12 November 1980 | Voyager 1 flyby; close pass of Titan |
| 26 August 1981 | Voyager 2 flyby; the probe then continues to Uranus |
| 1988 | The north polar hexagon is identified in Voyager images |
| September 1990 | A Great White Spot erupts and is imaged by Hubble |
| 1995–1996 | Earth crosses the ring plane; Hubble studies the edge-on rings |
| 15 October 1997 | Launch of Cassini-Huygens |
| 11 June 2004 | Cassini flies past Phoebe |
| 1 July 2004 | Cassini enters orbit around Saturn |
| 14 January 2005 | Huygens lands on Titan |
| 2005 | Cassini discovers the water plumes of Enceladus |
| 2006 | Cassini confirms lakes near Titan's north pole |
| August 2009 | Saturn's equinox; Spitzer announces the giant Phoebe ring |
| December 2010 | A great storm erupts in the northern hemisphere |
| 19 July 2013 | "The Day the Earth Smiled": Cassini photographs Earth from Saturn |
| 2015 | Cassini data confirm a global ocean beneath Enceladus' ice |
| 26 April 2017 | First of 22 Grand Finale dives |
| May 2017 | Northern summer solstice |
| 15 September 2017 | Cassini plunges into Saturn |
Recent discoveries: 2018 to today
| Date | Event |
|---|---|
| 2019 | Ring seismology gives a rotation period of about 10 h 33 min; 20 new moons announced |
| June 2019 | NASA selects Dragonfly |
| 21 December 2020 | Great conjunction of Jupiter and Saturn, 0.1 degree apart |
| 2023 | Phosphates found in Enceladus ice grains (Cassini data); 62 new moons announced; Webb images Saturn and Enceladus' plume |
| February 2024 | Cassini data suggest a young ocean inside Mimas |
| April 2024 | Dragonfly confirmed for construction |
| March 2025 | 128 new moons announced, total 274; Earth crosses the ring plane on 23 March |
| May 2025 | Saturn's equinox |
Looking ahead
| Date | Event |
|---|---|
| July 2028 | Planned launch of Dragonfly |
| 2034 | Planned arrival of Dragonfly at Titan |
| 2038–2039 | Next ring-plane crossing seen from Earth |
| 2040 | Next great conjunction of Jupiter and Saturn |
| Late 2030s or later | Possible launch of an Enceladus mission (concepts only, see future missions) |
FAQ
When was Saturn discovered?
Saturn was never "discovered": it is visible to the naked eye and has been observed since prehistoric times. Recorded observations go back to Babylonian astronomers of the 1st millennium BCE.
When were Saturn's rings discovered?
Galileo first saw them in 1610 without understanding what they were. Christiaan Huygens identified them as a ring in 1659.
What are the most important dates in Saturn exploration?
Pioneer 11's first flyby on 1 September 1979, the Voyager flybys of 1980 and 1981, Cassini's arrival on 1 July 2004, the Huygens landing on 14 January 2005 and Cassini's final plunge on 15 September 2017.
How many moons does Saturn have today?
274 confirmed moons since March 2025, when 128 new small moons were announced. The count may keep rising as telescopes find fainter objects.
Sources
- NASA Science: Saturn
- NASA Science: Cassini mission
- IAU Minor Planet Center
- Van Helden, A., "Saturn and his anses", Journal for the History of Astronomy 5, 1974