Tempel 1 (official designation: 9P/Tempel) is a periodic Jupiter-family comet discovered by

Wilhelm Tempel Ernst Wilhelm Leberecht Tempel (4 December 1821 – 16 March 1889), normally known as Wilhelm Tempel, was a German astronomer who worked in Marseille until the outbreak of the Franco-Prussian War in 1870, then later moved to Italy. Tempel was ...

in 1867. It completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the ''Deep Impact'' space mission, which photographed a deliberate high-speed impact upon the comet in 2005. It was re-visited by the ''Stardust'' spacecraft on February 14, 2011 and came back to perihelion in August 2016.

Discovery and orbital history

Tempel 1 was discovered on April 3, 1867, by

, who was working at

Marseille Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Fra ...

. At the time of discovery, it approached

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

once every 5.68 years (designations 9P/1867 G1 and 1867 II). It was subsequently observed in 1873 (9P/1873 G1, 1873 I, 1873a) and in 1879 (1879 III, 1879b). Photographic attempts during 1898 and 1905 failed to recover the comet, and astronomers surmised that it had disintegrated, when in reality, its orbit had changed. Tempel 1's orbit occasionally brings it sufficiently close to

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 ...

to be altered, with a consequent change in the comet's orbital period. This occurred in 1881 (closest approach to Jupiter of 0.55 AU), lengthening the orbital period to 6.5 years.

Perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

also changed, increasing by 50 million kilometres, rendering the comet far less visible from

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 ...

Tempel 1 was rediscovered in 1967 (as 9P/1967 L1, 1966 VII), after British astronomer

Brian G. Marsden Brian Geoffrey Marsden (5 August 1937 – 18 November 2010) was a British astronomer and the longtime director of the Minor Planet Center (MPC) at the Center for Astrophysics Harvard & Smithsonian (director emeritus from 2006 to 2010). ...

performed precise calculations of the comet's orbit that took into account Jupiter's perturbations. Marsden found that further close approaches to Jupiter in 1941 (0.41 AU) and 1953 (0.77 AU) had decreased both the perihelion distance and the orbital period to values smaller than when the comet was initially discovered (5.84 and 5.55 years, respectively). These approaches moved Tempel 1 into its present

libration In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. It permits an observer to see slightly different hemispheres of the surface at different tim ...

around the 1:2 resonance with Jupiter. Despite an unfavorable 1967 return, Elizabeth Roemer of the Catalina Observatory took several photographs. Initial inspection revealed nothing, but in late 1968 she found a June 8, 1967 exposure (Tempel 1 had passed perihelion in January) that held the image of an 18th magnitude diffuse object very close to where Marsden had predicted the comet to be. At least two images are required for orbit computation, so the next return had to be awaited. Roemer and L. M. Vaughn recovered the comet on January 11, 1972, from Steward Observatory (9P/1972 A1, 1972 V, 1972a). The comet became widely observed, reached a maximum brightness of magnitude 11 during May, and was last seen on July 10. Since that time the comet has been seen at every apparition, in 1978 (1978 II, 1977i), 1983 (1983 XI, 1982j), 1989 (1989 I, 1987e1), 1994 (1994 XIUX, 1993c), 2000 and 2005. Its orbital period is 5.515 years.

Physical characteristics

Tempel 1 is not a bright comet; its brightest

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 ...

since discovery has been 11, far below naked-eye visibility. Its nucleus measures . Measurements taken by the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

in visible light and the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, ...

in infrared light suggest a low

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refle ...

of only 4%. A two-day rotation rate was also determined.

Exploration

''Deep Impact'' space mission

On 4 July 2005 at 05:52 UTC (01:52 EDT), Tempel 1 was deliberately struck by one component of the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

''Deep Impact'' probe, one day before perihelion. The impact was photographed by the other component of the probe, which recorded a bright spray from the impact site. The impact was also observed by earthbound and space telescopes, which recorded a brightening of several magnitudes. The

crater Crater may refer to: Landforms * Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet * Explosion crater, a hole formed in the ground produced by an explosion near or below the surf ...

that formed was not visible to ''Deep Impact'' due to the cloud of dust raised by the impact, but was estimated to be between 100 and 250 meters in diameter and 30 meters deep. The probe's spectrometer instrument detected dust particles finer than human hair, and discovered the presence of

silicates 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 ...

, carbonates, smectite, metal sulfides (such as fool's gold), amorphous carbon and polycyclic aromatic hydrocarbons. Water ice was detected in the

ejecta Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma ...

. The water ice came from 1 meter below the surface crust (the devolatized layer around the nucleus).

NEXT mission

In part because the crater formed during the ''Deep Impact'' collision could not be imaged during the initial flyby, on 3 July 2007, NASA approved the New Exploration of Tempel 1 (or NExT) mission. The low-cost mission utilized the already existing ''Stardust'' spacecraft, which had studied Comet Wild 2 in 2004. ''Stardust'' was placed into a new orbit so that it approached Tempel 1. It passed at a distance of approximately on February 15, 2011, 04:42 UTC. This was the first time that a comet was visited twice. On February 15, NASA scientists identified the crater formed by ''Deep Impact'' in images from ''Stardust''. The crater is estimated to be in diameter, and has a bright mound in the center likely created when material from the impact fell back into the crater
Energy of impactor
According to NASA "The impactor delivers 19 Gigajoules (that's 4.8 tons of TNT) of kinetic energy to excavate the crater. This kinetic energy is generated by the combination of the mass of the impactor (370 kg; 816 lbs) and its velocity when it impacts (~10.2 km/s)". According to NASA, "The energy from the impact will excavate a crater approximately 100m wide and 28m deep". The geometry of the flyby allowed investigators to obtain considerably more three-dimensional information about the nucleus from stereo pairs of images than during ''Deep Impacts encounter. Scientists were able to quickly spot locations where an elevated flow-like formation of

icy Icy commonly refers to conditions involving ice, a frozen state, usually referring to frozen water. Icy or Icey may also refer to: People * Icy Spicy Leoncie, an Icelandic-Indian musician Arts, entertainment, and media Music * ICY (band), a vo ...

material on the comet's surface receded due to sublimation between encounters.

Close approaches

Comets are in unstable orbits that evolve over time due to perturbations and

outgassing Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the release of a gas that was dissolved, trapped, frozen, or absorbed in some material. Outgassing can include sublimation and evaporation (which ...

. Tempel 1 passed within 0.04 AU – or 5.9 million km (3.7 million mi) – of the

dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to ...

Ceres on November 11, 2011. Then, as a Jupiter-family comet, it will spend years interacting with the

giant planet The giant planets constitute a diverse type of planet much larger than Earth. They are usually primarily composed of low-boiling-point materials (volatiles), rather than rock or other solid matter, but massive solid planets can also exist. The ...

Jupiter, finally passing within 0.02 AU – or 3.0 million km (1.9 million mi) – of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

on October 17, 2183.

Gallery

StardustTemple1.jpg, Tempel 1 from the ''Stardust'' spacecraft in 2011 PIA13862 Tempel 1 annotated.jpg, Comparison of ''Deep Impact'' and ''Stardust'' photos of a smooth elevated feature on the surface of the nucleus showing recession of icy cliffs at the margins.

References

External links

Space.com - ''Deep Impact''NASA - ''Deep Impact''NASA - ''Stardust''-NExT

Tempel 1 natural/contrast-enhanced

Four views of Tempel 1
{{DEFAULTSORT:Tempel, 009P Periodic comets 0009 Comets visited by spacecraft Comets in 2011 Comets in 2016 18670403