Matches in DBpedia 2014 for { <http://dbpedia.org/resource/Color_index> ?p ?o. }
Showing items 1 to 42 of
42
with 100 items per page.
- Color_index abstract "In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. To measure the index, one observes the magnitude of an object successively through two different filters, such as U and B, or B and V, where U is sensitive to ultraviolet rays, B is sensitive to blue light, and V is sensitive to visible (green-yellow) light (see also: UBV system). The set of passbands or filters is called a photometric system. The difference in magnitudes found with these filters is called the U-B or B–V color index, respectively. The smaller the color index, the more blue (or hotter) the object is. Conversely, the larger the color index, the more red (or cooler) the object is. This is a consequence of the logarithmic magnitude scale, in which brighter objects have smaller (more negative) magnitudes than dimmer ones. For comparison, the yellowish Sun has a B–V index of 0.656 ± 0.005, while the bluish Rigel has a B–V of –0.03 (its B magnitude is 0.09 and its V magnitude is 0.12, B–V = –0.03).In principle, the temperature of a star can be calculated directly from the B-V index, and there are in the literature several formulae to make this connection. A good approximation can be obtained by considering stars as black bodies, using Ballesteros' formula:Color indices of distant objects are usually affected by interstellar extinction —i.e. they are redder than those of closer stars. The amount of reddening is characterized by color excess, defined as the difference between the Observed color index and the Normal color index (or Intrinsic color index), the hypothetical true color index of the star, unaffected by extinction.For example, in the UBV photometric system we can write it for the B-V color:The passbands most optical astronomers use are the UBVRI filters, where the U, B, and V filters are as mentioned above, the R filter passes red light, and the I filter passes infrared light. This system of filters is sometimes calledthe Johnson-Cousins filter system, named after the originators of the system (see references). These filters were specified as particular combinations of glass filters and photomultiplier tubes. M. S. Bessell specified a set of filter transmissions for a flat response detector, thus quantifying the calculation of the color indices. For precision, appropriate pairs of filters are chosen depending on the object's color temperature: B-V are for mid-range objects, U-V for hotter objects, and R-I for cool ones.".
- Color_index wikiPageExternalLink nph-bib_query?bibcode=1953ApJ...117..313J&db_key=AST&high=3c321cbf8303780.
- Color_index wikiPageExternalLink nph-bib_query?bibcode=1974MNRAS.166..711C&db_key=AST&high=3c321cbf8304063.
- Color_index wikiPageExternalLink nph-bib_query?bibcode=1974MNSSA..33..149C&db_key=AST&high=3c321cbf8304063.
- Color_index wikiPageExternalLink nph-bib_query?bibcode=1990PASP..102.1181B&db_key=AST&high=3c321cbf8304649.
- Color_index wikiPageID "30871458".
- Color_index wikiPageRevisionID "590197075".
- Color_index hasPhotoCollection Color_index.
- Color_index subject Category:Index_numbers.
- Color_index subject Category:Photometric_systems.
- Color_index type Artifact100021939.
- Color_index type Instrumentality103575240.
- Color_index type Object100002684.
- Color_index type PhotometricSystems.
- Color_index type PhysicalEntity100001930.
- Color_index type System104377057.
- Color_index type Whole100003553.
- Color_index comment "In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. To measure the index, one observes the magnitude of an object successively through two different filters, such as U and B, or B and V, where U is sensitive to ultraviolet rays, B is sensitive to blue light, and V is sensitive to visible (green-yellow) light (see also: UBV system). The set of passbands or filters is called a photometric system.".
- Color_index label "Color index".
- Color_index label "Farbindex".
- Color_index label "Indice de couleur".
- Color_index label "Indice di colore".
- Color_index label "Kleurindex".
- Color_index label "Wskaźnik barwy".
- Color_index label "Показатель цвета".
- Color_index label "色指数".
- Color_index label "色指數".
- Color_index sameAs Barevný_index.
- Color_index sameAs Farbindex.
- Color_index sameAs Indice_de_couleur.
- Color_index sameAs Indeks_warna.
- Color_index sameAs Indice_di_colore.
- Color_index sameAs 色指数.
- Color_index sameAs 색지수.
- Color_index sameAs Kleurindex.
- Color_index sameAs Wskaźnik_barwy.
- Color_index sameAs m.025tt44.
- Color_index sameAs Q271860.
- Color_index sameAs Q271860.
- Color_index sameAs Color_index.
- Color_index wasDerivedFrom Color_index?oldid=590197075.
- Color_index isPrimaryTopicOf Color_index.