Monday, March 18, 2019
Stars :: essays research papers
STARSThe magnitude scale was invented by an ancient Greek astronomer named Hipparchus in nearly 150 BC He ranked the stars he could see in terms of their ignitor, with 1 representing the hopefulest down to 6 representing the expireest. Modern astronomy has extended this system to stars brighter than Hipparchus first magnitude stars and ones much, much fainter than 6. As it turns out, the eye senses brightness logarithmically, so for each one increase in 5 magnitudes corresponds to a decrease in brightness by a factor 100. The absolute magnitude is the magnitude the stars would lay down if viewed from a distance of 10 parsecs or some 32.6 light years. Obviously, Deneb is intrinsically very bright to make this list from its greater distance. Rigel, of nearly the corresponding absolute magnitude, but closer, stands even higher in the list. Note that virtually of these distances atomic number 18 really nearby, on a cosmic scale, and that they be broadly speaking uncertain b y at least 20%. All stars be variable to some extent those which are visibly variable are marked with a "v". What are unpatterned and absolute magnitudes? patent is how bright the appear to us in the sky. The scale is somewhat arbitrary, as explained above, but a magnitude difference of 5 has been rope to barely a factor of 100 in intensity. Absolute magnitudes are how bright a star would appear from some standard distance, arbitrarily set as 10 parsecs or about 32.6 light years. Stars can be as bright as absolute magnitude -8 and as faint as absolute magnitude +16 or fainter. There are thus (a very few) stars more than 100 times brighter than Sirius, while scarcely any are known fainter than Wolf 356.Star, large celestial dead body composed of gravitationally contained hot gases emitting electromagnetic radiation, especially light, as a result of nuclear reactions inside the star. The sun is a star. With the sole exception of the sun, the stars appear to be fixed, mai ntaining the same pattern in the skies year aft(prenominal) year. In fact the stars are in rapid motion, but their distances are so great that their relative changes in position become apparent only over the centuries.The number of stars visible to the naked eye from body politic has been estimated to total 8000, of which 4000 are visible from the northern hemisphere and 4000 from the southern hemisphere. At any one time in either hemisphere, only about 2000 stars are visible.