Star yellow: examples, the difference of stars in color
Any star - yellow, blue or red -is a hot glow ball. The modern classification of luminaries is based on several parameters. These include surface temperature, size and brightness. The color of the star, visible at a clear night, depends mainly on the first parameter. The hottest stars are blue or even blue, the coldest are red. Yellow stars, examples of which are named below, occupy the middle position on the temperature scale. The sun enters into the number of these stars.
Differences
The bodies heated to different temperatures radiatelight from an unequal long wave. The color determined by the eye of a person depends on this parameter. The shorter the wavelength, the hotter body and the closer its color to white and blue. This is true for the stars.
The red lights are the coldest. The temperature of their surface reaches only 3 thousand degrees. The star is yellow, like our Sun, already hotter. Its photosphere is heated to 6000º. White luminaries are hot even more - from 10 to 20 thousand degrees. And, finally, the blue stars are the hottest. The temperature of their surface reaches from 30 to 100 thousand degrees.
General characteristics
Yellow stars, the names of many of which are goodknown to people far from astronomy, found scientists in large numbers. They differ in size, mass, luminosity and some other characteristics. Common to such luminaries is the surface temperature.
The yellow color of the luminary can be acquired in the processevolution. However, the vast majority of such stars are located on the main sequence of the Hertzsprung-Russell diagram. These are the so-called yellow dwarfs, to which the Sun belongs.
The main star of the system
Dwarfs such luminaries are called because of the relatively small size. The diameter of the Sun averages 1.39 * 109 m, weight - 1.99 * 1030 kg. Both parameters significantly exceed the analogous characteristics of the Earth, but in outer space are not something out of the ordinary. There are other yellow stars, examples of which are given below, considerably ahead of the Sun in size.
The surface temperature of our luminary reaches6 thousand Kelvin. The sun belongs to the spectral class G2V. In fact, it emits almost pure white light, but due to the nature of the planet's atmosphere, the short-wave part of the spectrum is absorbed. The result is a yellow tint.
Features of the yellow dwarf
Small in size luminaries are characterized byan impressive life expectancy. The average value of this parameter is 10 billion years. The sun is now located approximately at the middle of the life cycle, that is, before leaving the Main sequence and turning into a red giant, it remains about 5 billion years.
The star, yellow and belonging to the type of "dwarfs"has dimensions similar to solar ones. The source of energy of such luminaries is the synthesis of helium from hydrogen. The next stage of evolution, they pass after the nucleus ends in hydrogen and starts burning helium.
In addition to the Sun, the yellow dwarfs include Alpha Centauri A, Alpha North Crown, Myu Beopas, Tau Ceti and other luminaries.
Yellow sub-giants
Stars, similar to the Sun, after exhaustionhydrogen fuel, begin to change. When the core lights up, helium will expand and turn into a red giant. However, this stage does not come immediately. First, the outer layers begin to burn. The star has already descended from the Main sequence, but has not yet expanded - it is in the sub-gigant stage. The mass of such a luminary usually varies from 1 to 5 solar masses.
The stage of the yellow sub-gigant can also pass through more impressive stars. However, for them, this stage is less pronounced. The most famous sub-gigant for today is Procyon (Alpha Small Dog).
A real rarity
Yellow stars, whose names were cited above,belong to a fairly common in the universe types. Otherwise, things are going on with hyper-giants. These are real giants, considered to be the heaviest, brightest and largest and at the same time possessing the shortest lifespan. Most of the known hypergigants are bright blue variables, but there are white, yellow stars and even red ones among them.
Among such rare cosmic bodies is,for example, Ro Cassiopeia. It is a yellow hypergigant, according to luminosity 550,000 times ahead of the Sun. From our planet it is removed by 12,000 light years. On a clear night, you can see it with the naked eye (visible luster - 4,52m).
Supergiants
Hypergigants are a particular case of supergiants. The latter also includes yellow stars. They, in the opinion of astronomers, are a transitional stage of the evolution of the stars from the blue to the red supergiant. Nevertheless, in the yellow supergiant stage, the star can survive long enough. As a rule, at this stage of evolution, the luminaries do not perish. During the entire study of outer space, only two supernovae generated by the yellow supergiants were recorded.
Such luminaries include Canopus (Alfa Kiel), Rastaban (Beta Dragon), Betu Aquarius and some other objects.
As you can see, each star, yellow like the Sun,has specific characteristics. However, everyone has something in common - a color that is the result of heating the photosphere to certain temperatures. In addition to those named, Epsilon Shchita and Beta Crow (bright giants), the Delta of the South Triangle and Betu Girafa (supergiants), the Chapel and the Windemiatrix (giants), and many other cosmic bodies are also referred to similar luminaries. It should be noted that the color denoted in the classification of the object does not always coincide with the visible color. This is because the true shade of light is distorted due to gas and dust, and also after passing through the atmosphere. The spectrograph is used to determine the color of astrophysics: it gives much more accurate information than the human eye. It is thanks to him that scientists can distinguish between blue, yellow and red stars, distant from us for huge distances.
