Tempel 1

Tempel 1 ( official designation 9P/Tempel ) is a short- period comet, which was investigated by the NASA Deep Impact spacecraft in the summer of 2005.

• 8.1 Background Information

Discovery

The comet Tempel 1 was discovered on April 3, 1867 in the observatory of Marseilles by the Saxon astronomer and lithographer Ernst Wilhelm Leberecht temple. Subsequent calculations showed that he was at that time 0.71 astronomical units (AU ) from Earth and 1.64 AU from the sun. Temple described at the time that the comet had an apparent diameter of 4 to 5 arc minutes.

Orbit

At the time of its discovery, the comet had an orbital period of approximately 5.7 years. In 1881 the comet approached up to 0.55 AE to the planet Jupiter, the orbit of the comet has been modified by the gravitational effect of the planet that the orbital period has lengthened to 6.5 years. Through this web change the comet was initially lost. As its orbit could be calculated taking into account the path interference by the planet in the 1960s, showed that the comet in the meantime two more times at Jupiter approached (1941 to 0.41 in 1953 to 0.77 AE and AE ), so that his turnaround time was shortened to around the present-day value of 5.5 years. Under these new provisions track the comet could subsequently be discovered in December 1968 on a photographic plate in June 1967. The retrieval was finally confirmed with the return of the comet in 1972. Currently he is at perihelion 1.506 AU and aphelion distance 4.738 AU from the sun and its orbital inclination to the ecliptic is 10,530 °.

Deep Impact spacecraft

During his appearance in the summer of 2005 the comet Tempel 1 was examined not only of telescopes, but also by the Deep Impact spacecraft. The spacecraft, NASA began a 372 kg heavy, large fridge projectile free, hit the comet nucleus, and observed the impact of this so-called impactor from a distance of about 8600 km. Here, about 4500 images were taken. Subsequently, the spacecraft passed the comet about 500 m distance, but no observations was able to perform, as their instruments to protect against the ejected particles had to be turned away from the comet. The event was also observed by several space-based and earth telescopes.

Results

The size of the comet could be determined by the recordings of the spacecraft to 7.6 × 4.9 km and its albedo by 0.04.

Before the impact of the impactor, the scientists were in the dark about whether he evoke a classic impact craters penetrate its mark in the comet or would even destroy the entire comet.

The output of the mission turned out to be rather conventional. Shortly after the impact of the impactor, first, a thermal flash has been observed where the floor has been explosively destroyed. As a result of the explosion, a fountain rose from about 3,500 ° C on hot, molten core material with a total mass of about four tons and a speed of 5-8 km / s. While formed on the nucleus of an impact crater with an estimated diameter of about 100 (-50 / 100 ) meters and a depth of about 30 meters, more 10,000 to 20,000 tons of material were ejected, of which 3,000 to 6,000 tons of dust. Thus, Tempel 1 has no hard crust, but is surrounded by a soft layer of dust.

The released gas spread with 1 km / s and more, while the dust particles were significantly slower at speeds between 10 and 400 m / s. The bulk of the dust ( about 80 %) therefore fell back to the core, the remaining dust and gas were in the comet's coma, and subsequently in interplanetary space are submitted. Unexpectedly, powdery material was ejected so much that the view was completely obscured on the resulting crater. Therefore, the size of the crater could only be estimated from the mass of the released material. Images of the mission Stardust - NExT show the crater, which has about 150 m in diameter and has a central mountain.

From the trajectory of the ejected dust was the density of the nucleus to 0.62 ( 0.47 / -0.33 ) g/cm3 - about two-thirds the density of water ice - to be determined. The nucleus appears to consist of porous and brittle material; approximately between 50 % and 70 % of the comet are empty space. On the surface of the core, the surface temperature was between 56 ° C and -13 ° C, traces were detected in some remote areas of water ice. In the spectrum of the ejecta but water could also be found, such as carbon dioxide, carbonates, complex organic compounds ( such as polycyclic aromatic hydrocarbons), silicates (such as the mineral olivine ) and clay minerals. In any case, the solid components against the volatile elements seem to prevail, so that comets, which until then often snowballs ( dirty snowballs ) were described as dirty, are more likely to be regarded as snowy dirtballs ( icy dirt balls).

The composition and amount of ejecta is reminiscent of some already examined the Oort cloud comets. May therefore come from some comets from the Kuiper belt, including one temple, near the gas giant region of the protoplanetary disk. This would suggest a common origin for today distant comets far from the Sun.

One surprise was that the surface of the comet since its emergence not only of impact craters - which were observed here for the first time in a comet - and unevenness is marked by loss of ice and sun warming. It could also have different geological layers are observed, reminiscent of the comet-like Saturn's moon Phoebe. Thus, comets could be subject to certain geological processes, or Tempel 1 have originated from the merger of two different bodies.

Stardust spacecraft

A further investigation of the comet by a space probe happened on February 14, 2011. The Stardust spacecraft, which is on the road since 1999, the comet came extremely close. She flew in only 181 km Distance to "Temple 1" over. The pictures taken by the probe will be compared with those of the Deep Impact to see what and how much has changed has. In this way, should therefore be started to unravel the story of a comet's surface. Besides the photos, the spacecraft obtains information about the composition and amount of dust particles that are secreted from the comet "Temple 1". The researchers want to learn in this way, as the heavenly bodies is formed millions of years ago.