Asteroids

Information about Asteroids

Published on December 23, 2009

Author: jesudass

Source: authorstream.com

Content

ASTEROIDS : ASTEROIDS Submitted By P.A.Nandhini REG No. 09IT30 CIT Sign Asteroid-Intro : Asteroid-Intro Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System. They are smaller than planets but larger than meteoroids. Traditionally, small bodies orbiting the Sun were classified as asteroids, comets or meteoroids. Asteroid Belt : Asteroid Belt Over 100,000 objects greater than 10 km. now identified in the Main Belt Total mass less than 1% of moon’s mass Over 100 NEAs greater than 1 km. across are being tracked; probably part of a population of about 2000 Kirkwood gap (and others) occur in the belt where there are orbital resonances with Jupiter Asteroids classified by spectral group Formation : Formation It is believed that planetesimals in the main asteroid belt evolved much like the rest of the Solar Nebula until Jupiter neared its current mass. Both simulations and a discontinuity in spin rate and spectral properties suggest that asteroids larger than approximately 120 km (75 mi) in diameter accreted during that early era. smaller bodies are fragments from collisions between asteroids during or after the Jovian disruption. Characteristics : Characteristics Objects in the main asteroid belt vary greatly in size, from a diameter of 950 kilometres for the dwarf planet Ceres and over 500 kilometres for the asteroids. A few of the largest are roughly spherical and are very much like miniature planets. The vast majority, however, are much smaller and are irregularly shaped. The physical composition of asteroids is varied . Ceres appears to be composed of a rocky core covered by an icy mantle, whereas Vesta is thought to have a nickel-iron core, olivine mantle, and basaltic crust. How to Classify Asteroids : How to Classify Asteroids Glass (or a fine mist of water droplets) separates lignt into separate wavelengths due to ‘differential refraction Eyes are sensitive to brightness variations (rod cells) and 3 colors (R, G, B cone cells) S Asteroids (‘silicaceous’) : S Asteroids (‘silicaceous’) 951 Gaspra 433 Eros (true color) Ida (and Dactyl) 19 x 12 x 11 km 33 x 13 x13 km 58 x 23 km (1km) Galileo flyby, 199 NEAR orbit/landing Galileo flyby, 1993 Grooves, curved near-Earth asteroid, member of Koronis depressions, ridges space weathering family, first ID of (Phobos-like) . effects documented. asteroid ‘moons’. C Asteroids (‘carbonaceous’) : C Asteroids (‘carbonaceous’) 253 Mathilde; 66 x 48 x 46 km, visited by NEAR Shoemaker Surface as dark as charcoal; typical outer belt asteroid What is in the Asteroid Threat? : What is in the Asteroid Threat? Controversial until late 20th century; few NEAs were known, spectral matches between asteroids and meteorites were poor, and no known mechanism could account for their delivery from the asteroid belt. Recognition of ‘chaos’, extreme sensitivity to initial conditions, as fundamental to most natural processes, especially for orbital dynamics (Comet SL 9, 1994). What is in the Asteroid Threat? : What is in the Asteroid Threat? Collisional (orbital) and radiation (space weathering, Yarkovsky effect) processes become important to objects in asteroid belt over billions of years. Combination of processes provides a ‘conveyer belt’ of (reddened) material to Earth orbit. Must look to geology for ‘ground truth’ – what is the evidence for impact, size-frequency distribution of impacting bodies? Asteroid Belt : Asteroid Belt The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter where 98.5% of the known minor planet orbits can be found Asteroids, or minor planets, are small celestial bodies composed of rock, ice, and some metal that orbit the Sun. This region is termed the main belt when contrasted with other concentrations of minor planets, since these may also be termed asteroid belts. Asteroid Moon : Asteroid Moon An asteroid moon is an asteroid that orbits another asteroid as its natural satellite. It is thought that many asteroids may possess moons, in some cases quite substantial in size. Discoveries of asteroid moons (and binary objects, in general) are very important because the determination of their orbits provides estimates (or at least constraints) on their density and mass allowing an insight into their physical properties, impossible otherwise. Three views of Vesta : Three views of Vesta Hubble image, model and color-shaded topography Largest member of V class of asteroids (vestoids) Spectral variations consistent with HEDs THANK YOU : THANK YOU

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