Conglomeration of frozen water and gases (methane, ammonia, CO2) and silicates that that formed in the outer solar system and orbits the Sun. In recent years, the description of comets has shifted from dirty snowballs to snowy dirtballs with more dust than ice. However, the ratio is less than 10-to-1. with 76-year The length of time it takes an orbiting object to make one complete trip around its primary body. The Earth’s orbital period around the Sun is 1 year and the Moon's is one 27.3 days. Mercury's orbital period is ~88 days (closest to the Sun) and Neptune's is ~165 years. Images returned by the Giotto Mission revealed its Core of an atom, where nearly the entire mass and all positive charge is concentrated. It consists of protons and neutrons. was a dark (Ratio of the amount of light reflected by an object and the amount of incident light. Albedo is used as a measure of the reflectivity or intrinsic brightness of an object. A white, perfectly reflecting surface has an albedo of 1.0 while a black perfectly absorbing surface would have an 0.04-0.05), peanut-shaped body, ~15 km long and 7-10 km wide; the measured Mass of an object divided by its volume. Density is a characteristic property of a substance (rock vs. ice, e.g.). Some substances (like gases) are easily compressible and have different densities depending on how much pressure is exerted upon them. The Sun is composed of compressible gases and is much (0.3 g/cm3) indicated a fluffy porous texture. The black surface is composed of Pertaining to C-containing compounds. Organic compounds can be formed by both biological and non-biological (abiotic) processes. compounds. Giotto imaged 7 jets on the warmer sunlit side (ejecting ~3 tonnes/s of material), but only ~10% of the surface was active. The jets gave the comet a strange, wobbling rotation. H2O accounted for ~80 % of the ejected material with substantial amounts of CO (10 %), CO2 (2.5 %), CH4 and NH3. Traces of other hydrocarbons, Fe, and Na were also found. Two major classes of dust particles were found: one dominated by the light elements (C, H, O, N); the other rich in mineral-forming elements (Na, Mg, Si, Fe, Ca), which must have been derived from closer to the Our parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the than its ices. Light elements (except N) occurred in the same relative abundances as in the Sun, confirming that Comet Halley is made of primitive solar nebular material.
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