Vulcanoid asteroid

Vulkanoiden (also Vulcanoiden ) are hypothetical asteroids that might exist in a sparse " third asteroid belt " within the orbit of the planet Mercury.

Despite a long search programs their existence has not yet been proven. It results from theoretical considerations alone for the time being for stability weakly eccentric orbits in the ecliptic between the Sun and Mercury. As a further indication of the fact one can evaluate that Mercury was exposed as a planet closest to the Sun in the early days of the solar system an intense bombardment by smaller celestial bodies.

Properties

The Vulkanoiden must, if they exist, be less than about 50 km in diameter, because larger bodies would otherwise have been the solar probe Solar and Heliospheric Observatory (SOHO ) have already discovered. Previously, it was found in this area, only a few asteroids in an extremely eccentric orbit ellipses, spending only a few percent of their circulation within the orbit of Mercury ( 1566) Icarus (1949, 0.19 to 1.97 AU) and the comet-like, from the IRAS Space Telescope in 1984 discovered (3200) Phaethon ( 0.14 to 2.40 AE). He is at perihelion about 200 km / s and quickly heats up to about 850 K [ESA 2002].

Possible preferred train areas of Vulkanoiden were calculated at 0.18 and 0.15 AU distance from the Sun. Like the rings of Saturn or the asteroid belt would also have a Vulkanoidengürtel Kirkwood gaps and concentrations.

Search

Already about 100 years sought the then " record holder " of discovered asteroids, the Bohemian- Austrian astronomer Johann Palisa, during an eclipse expedition to the South Seas after Vulcan, a hypothetical "Intra -Mercury ". Although his search was unsuccessful, but it was now this small bodies analogous designation.

Particularly difficult is the discovery and observation of Vulkanoiden from the surface due to its perihelion, because it would be seen only in the twilight area of ​​on - and the setting sun. Alternatively, the solar neighborhood would scan at a total solar eclipse. Large telescopes are unsuitable for such search programs, because the sensitive optics would be destroyed by high possible light. The use of space-based telescopes is hampered by high costs that would be responsible more for the search of any collision- prone near-Earth objects ( NEOs).

Meanwhile, the search is therefore intensified by high-altitude aircraft from the infrared region, because it is likely that bodies are very hot this close to the sun and emit significant heat radiation. Are expected surface temperatures of 700 K to 900 K.