Tuesday, May 25, 2010

=RED GIANT=

Posted by Louisa at 10:42 AM


A red giant is a luminous giant star of low or intermediate mass.An evolved giant star with a surface temperature of 2,500 to 3,500°C, a spectral type of M or K, and a diameter between 10 and 100 times times that of the Sun.


Red giants represent a late stage in the evolution of stars with a range of masses, from just under the mass of the Sun to tens of solar masses.The largest red giants, which form from the most massive of stars, are known as red supergiants. A red giant has exhausted its core supply of hydrogen and is now fusing hydrogen to helium in a shell outside the core. The nearest red giant to the Sun is Gacrux.
Although red giants are quite common among the stars visible to the naked eye, they are actually quite rare in space. This is because they last for only a small fraction of a star's life. According to the newspaper article that I read once, the last Red Giant seen was in 1999.

Only a few red giants have well determined masses. The mass of a star can be measured directly only if the star has a binary companion. In the case of a red giant, the companion would have been swallowed up if it was too close to the evolving star. If it was much further away, the orbital period would be centuries or more and hence less easy to determine accurately.

The radii of red giants are not only difficult to measure but are also difficult to define, because of the tenuous nature of the stars' atmospheres. At wavelengths at which the atmosphere is very opaque, the star looks much larger. Good progress is now being made, however, using optical and infra-red interferometers to resolve and measure the diameters of these stars.

Red Giants are rare to be seen in the sky, and yet it's so beautiful.. Good things in life never appear often, hence, we have to appreciate everything in our lives, and stop complaining about every little thing.


for more info on RED GIANT, surf on
1) www.historyoftheuniverse.com/starold.html
2) www.daviddarling.info/encyclopedia/R/redgiant.html

 

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