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Comets and asteroids

Comets have been observed for thousands of years, and asteroids for more than 200 years. Over 2500 comets (more than 1200 of which have been discovered by the SOHO satellite) and more than 370000 asteroids have been discovered. These bodies have traditionally been studied using ground-based optical means.

However, radar has now come into its own (through the imaging of surfaces and the detection of asteroid satellites) and spacecraft have carried out studies of the surfaces and environments of various asteroids and comets. Space missions are in progress and being planned in order to visit asteroids and comets in order to collect and return samples to Earth. These missions are important because comets are considered to be composed of pristine material unaltered from the time of formation of the planets.

Developments over the last few decades in this field include: the extraordinary impact of Comet D/1993 F2 (Shoemaker-Levy 9) on the planet Jupiter in 1994 July, the spectacular encounter of the Deep Impact spacecraft with Comet 9P/Tempel in 2005, the discovery of asteroid satellites, and the discovery of objects belonging to the Kuiper belt in the outer solar system.

The last few decades or so have also thrown light on a reason for the demise of the dinosaurs (at the Cretaceous-Tertiary boundary 65 million years ago) as being due to an asteroid (or asteroids) colliding with the Earth. The crater of the main impactor has been found in Central America at Chicxulub.

Inspec provides coverage of comets and asteroids, their observations and properties. In Section A (Physics Abstracts), the following parts of the classification scheme contain the relevant information:

A9190: Other topics in solid Earth physics (used for impacts and meteorite craters)

A9460Q: Solar wind interaction with Moon, planets, satellites, and comets

A9510J: Astrometry and spherical astronomy

A9555L: Aerospace instrumentation (used for spacecraft/balloon/rocket equipment)

A9555P: Lunar, planetary, and deep space probes

A9580D: Radio, radar, and microwave astronomical observations

A9580E: Sub-millimetre astronomical observations (used for 300-1000 microns range)

A9580G: Infrared astronomical observations (used for 1-300 microns range)

A9580J: Photographic region astronomical observations (used for ground-based UV up to 1-micron range)

A9580M: Space ultraviolet astronomical observations

A9630H: Asteroids

A9630T: Other planets (used for trans-Neptunian objects, Plutinos, Cubewano objects, Kuiper Belt objects, Oort Cloud objects, scattered disk objects)

A9635: Planetary and satellite characteristics and properties (used for comet and asteroid characteristics and properties)

A9650G: Comets

A9650K: Meteors, showers and meteoroids

The most important controlled terms from the Thesaurus are:

• asteroids

• astrometry

• astronomical ephemerides

• astronomical instruments

• astronomical photometry

• astronomical polarimetry

• astronomical spectra

• astrophysical plasma

• astrophysical jets

• cometary nuclei

• comets

• cosmic dust

• infrared astronomy

• interplanetary magnetic fields

• Kuiper belt objects

• meteorite craters

• meteoroids

• meteors

• planetary atmospheres

• planetary interiors

• planetary magnetism

• planetary remote sensing

• planetary satellites

• planetary surfaces

• radioastronomy

• solar wind

• space vehicles

• submillimetre astronomy

• ultraviolet astronomy

• astronomy


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