4179 Toutatis, provisional designation , is an elongated, stony

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

and slow rotator, classified as a

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (Apsis, perihelion) is less than 1.3 astronomical unit ...

and potentially hazardous asteroid of the

Apollo asteroid The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth ...

and Alinda asteroid groups, approximately 2.5 kilometers in diameter. Discovered by French astronomer

Christian Pollas Christian Pollas (b. 1947) is a French astronomer, known for the discovery and observation of minor planets and supernovae. Pollas is credited by the Minor Planet Center with the discovery of 26 asteroid An asteroid is a minor planet of th ...

at Caussols in 1989, the asteroid was named after

Toutatis Toutatis or Teutates is a Celtic god who was worshipped primarily in ancient Gaul and Britain. His name means "god of the tribe", and he has been widely interpreted as a tribal protector.Paul-Marie Duval (1993). ''Les dieux de la Gaule.'' Éditio ...

from Celtic mythology. Toutatis is also a Mars-crosser asteroid with a

chaotic Chaotic was originally a Danish trading card game. It expanded to an online game in America which then became a television program based on the game. The program was able to be seen on 4Kids TV (Fox affiliates, nationwide), Jetix, The CW4Kid ...

orbit produced by a 3:1

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscil ...

with the planet

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...

, a 1:4 resonance with the planet

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

, and frequent close approaches to the

terrestrial planet A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, ...

s, including Earth. In December 2012, Toutatis passed within about 18 lunar distances of Earth. The Chinese lunar probe

Chang'e 2 Chang'e 2 (; ) is a Chinese unmanned lunar probe that was launched on 1 October 2010. It was a follow-up to the Chang'e 1 lunar probe, which was launched in 2007. Chang'e 2 was part of the first phase of the Chinese Lunar Exploration Program, ...

flew by the asteroid at a distance of 3.2 kilometers and a relative velocity of 10.73 km/s. Toutatis approached Earth again in 2016, but will not make another notably close approach until 2069.

Properties

Toutatis was first sighted on 10 February 1934, as object 1934 CT, but lost soon afterwards. It remained a

lost asteroid A minor planet is "lost" when today's observers cannot find it, because its location is too uncertain to target observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observat ...

for several decades until it was rediscovered on 4 January 1989 by

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

, and was named after the

Celtic god The gods and goddesses of the pre-Christian Celtic peoples are known from a variety of sources, including ancient places of worship, statues, engravings, cult objects and place or personal names. The ancient Celts appear to have had a pantheon ...

of tribal protection

(Teutates). The name of this god is very familiar in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

due to the

catchphrase A catchphrase (alternatively spelled catch phrase) is a phrase or expression recognized by its repeated utterance. Such phrases often originate in popular culture and in the arts, and typically spread through word of mouth and a variety of mass ...

''Par Toutatis!'' by the Gauls in the

comics a medium used to express ideas with images, often combined with text or other visual information. It typically the form of a sequence of panels of images. Textual devices such as speech balloons, captions, and onomatopoeia can indicate ...

Asterix ''Asterix'' or ''The Adventures of Asterix'' (french: Astérix or , "Asterix the Gaul") is a ''bande dessinée'' comic book series about a village of indomitable Gaulish warriors who adventure around the world and fight the Roman Republic, wi ...

. The spectral properties suggest that this is an S-type, or stony asteroid, consisting primarily of

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is a ...

s. It has a moderate

Bond albedo The Bond albedo (or ''spheric albedo'' or ''planetary albedo'' or ''bolometric albedo''), named after the American astronomer George Phillips Bond (1825–1865), who originally proposed it, is the fraction of power in the total electromagnetic ra ...

of 0.13.

Radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

imagery shows that Toutatis is a highly irregular body consisting of two distinct lobes, with maximum widths of about 4.6 km and 2.4 km, respectively. It is hypothesized that Toutatis formed from two originally separate bodies which coalesced at some point, with the resultant asteroid being compared to a

rubble pile In astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the ...

. Its rotation combines two separate periodic motions into a non-periodic result; to someone on the surface of Toutatis, the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

would seem to rise and set in apparently random locations and at random times at the asteroid's horizon. It has a

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

around its long axis (P_ψ) of 5.38 days. This long axis is precessing with a period (P_φ) of 7.38 days. The asteroid may have lost most of its original angular momentum and entered into this tumbling motion as a result of the

YORP effect Yorp or YORP may refer to one of the following: * 54509 YORP, an Earth co-orbital asteroid * Yarkovsky–O'Keefe–Radzievskii–Paddack effect, a second-order variation on the Yarkovsky effect *Yorps, friendly one-eyed Martians from the Commander ...

Orbit

With a

semimajor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the lo ...

of 2.5294 AU, or roughly 2.5 times the distance between Earth and the Sun, Toutatis has a 3:1

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Jupiter and a near-1:4 resonance with Earth making it a member of the Alinda asteroid group. It thus completes one orbit around the Sun for every 4.02 annual orbits of Earth. The

gravitational perturbation In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body. The other forces can include a third (fourth, fifth, etc.) body, resistance, as from ...

s caused by frequent close approaches to the terrestrial planets lead to

behavior in the orbit of Toutatis, making precise long-term predictions of its location progressively inaccurate over time. Estimates in 1993 put the Lyapunov time horizon for predictability at around 50 years, after which the uncertainty region becomes larger with each close approach to a planet. Without the perturbations from the terrestrial planets the Lyapunov time would be close to 10,000 years. The initial observations that showed its chaotic behavior were made by

Wiśniewski Wiśniewski (; feminine: Wiśniewska, plural Wiśniewscy) is the third most common surname in Poland (111,174 people in 2009).Ministry of Interior (Poland). Statystyka najpopularniejszych nazwisk występujących w Polsce in 2009'' (The most popula ...

. The low

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Ea ...

(0.47°) of the orbit allows frequent transits, where the inner planets Mercury, Venus, Earth, and Mars can appear to cross the Sun as seen from the perspective of Toutatis. Earth did this in January 2009, July 2012, July 2016 and 2020.

Close approaches and collision risk

Toutatis makes frequent close approaches to Earth, with a currently minimum possible distance (Earth

MOID Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits of ...

) of just 0.006 AU (2.3 times as far as the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

). The approach on 29 September 2004 was particularly close, at 0.0104 AU (within 4 lunar distances) from Earth, presenting a good opportunity for observation, with Toutatis having an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of 8.8 at its brightest. A close approach of happened on 9 November 2008. The most recent close approach was on 12 December 2012, at a distance of , with a magnitude of 10.7. At magnitude 10.7, Toutatis was not visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to norma ...

, but just visible to experienced observers using high-end

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

. During the 2012 encounter Toutatis was recovered on 21 May 2012, by the Siding Spring Survey at

18.9. A close approach will be 5 November 2069, at . Given that Toutatis makes many close approaches to Earth, such as in 1992, 1996, 2000, 2004, 2008, 2012, and 2016, it is listed as a potentially hazardous object. With an

uncertainty parameter The uncertainty parameter ''U'' is introduced by the Minor Planet Center (MPC) to quantify the uncertainty of a perturbed orbital solution for a minor planet. The parameter is a logarithmic scale from 0 to 9 that measures the anticipated longit ...

of 0, the orbit of Toutatis is very well determined for the next few hundred years. The probability of the orbit intersecting Earth is essentially zero for at least the next six centuries. The likelihood of collision in the distant future is considered to be very small. As a planet-crossing asteroid, Toutatis is likely to be ejected from the inner Solar System within a few million years. In 2004 a chain e-mail falsely claimed that Toutatis had a 63% chance of impacting Earth then. In fact, Toutatis passed by at 1.5 million kilometres, or about four Earth–Moon distances, as predicted. In 2006 Toutatis came closer than 2 AU to Jupiter; its orbit lies inside of Jupiter's. In the 2100s, it will approach Jupiter many times at a similar distance.

Physical characteristics

Large amounts of data of Toutatis were obtained during

's flyby. Toutatis is not a monolith, but most likely a coalescence of shattered fragments. This bifurcated asteroid is shown to be mainly consisting of a head (small lobe) and a body (large lobe). The two major parts are not round in shape, and their surfaces have a number of large facets. In comparison with radar models, the proximate observations from Chang'e 2's flyby have revealed several remarkable discoveries concerning Toutatis, among which the presence of the giant basin at the big end appears to be one of the most compelling geological features, and the sharply perpendicular silhouette in the neck region that connects the head and body is also quite novel. A large number of boulders and several short linear structures are also apparent on the surface.

Giant basin

The giant basin at the big end of Toutatis has a diameter of ~805 m, suggesting that one or more impactors may have collided with it there. The most significant feature is the ridge around the largest basin. The wall of this basin has a relatively high density of lineaments, some of which seem to be concentric to the basin. These ridges are indicative of an internal structure of small bodies and most of the ridges near the largest basin at the big end are most likely related to the huge stress energy during impact.

Observation

Toutatis has been observed with radar imaging from the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science ...

and the

Goldstone Solar System Radar The Goldstone Solar System Radar (GSSR) is a large radar system used for investigating objects in the Solar System. Located in the desert near Barstow, California, it comprises a 500-kW X-band (8500 MHz) transmitter and a low-noise receiver on the ...

during the asteroid's prior Earth flybys in 1992, 1996, 2000, 2004, and 2008. It was also observed with radar during the December 2012 flyby and observed more distant flyby with radar in December 2016. After 2016, Toutatis will not pass close to Earth again until 2069. Resolution of the radar images is as fine as 3.75 m per pixel, providing data to model Toutatis's shape and spin state.

Exploration

The Chinese lunar probe

departed from the Sun–Earth L2 point in April 2012 and made a flyby of Toutatis on 13 December 2012, with closest approach being 3.2 kilometers and a relative velocity of 10.73 km/s, when Toutatis was near its closest approach to Earth. It took several pictures of the asteroid, revealing it to be a dusty red/orange color.

References

External links

More Chang'E 2 Toutatis flyby images
(Emily Lakdawalla : 2013/01/20)

(Planetary Society)
CCTV13 Special
(all in Mandarin)
China joined the interplanetary club by successfully imaging the asteroid Toutatis
( Franck Marchis, 14 December 2012)
Chinese space probe flies by asteroid Toutatis
(Xinhua 2012-12-15)
Surface Features of Asteroid Toutatis Revealed by Radar
(YouTube: JPLnews)

* ttp://www.solarviews.com/eng/toutatis.htm Interesting views of asteroid
Astrobiology Magazine article
(09/27/04)

(Gravity Simulator)

(Emily Lakdawalla 2012-12-06)

Size comparison

Chang'e 2 fly-by of Toutatis
Presentation from Small Bodies Assessment Group (SBAG) 8 meeting
Boulders on asteroid Toutatis as observed by Chang'e-2
(

arXiv arXiv (pronounced "archive"—the X represents the Greek letter chi ⟨χ⟩) is an open-access repository of electronic preprints and postprints (known as e-prints) approved for posting after moderation, but not peer review. It consists of ...

:1511.00766 : 3 Nov 2015) * * * {{DEFAULTSORT:Toutatis 004179 004179 Discoveries by Christian Pollas Named minor planets 004179 004179 20121213 004179 004179 20121212 19890104