The reason is due to the different production mechanism for the energy output from the star and the increased size of the Red Giant.
As a star moves into its Red Giant phase, after not being able to maintain gravitational equilibrium due to hydrogen begin exhausted in the core, the star begins to collapse. This collapse heats a hydrogen shell just outside the core (previously not available for fusion) initiating fusion of hydrogen to helium in the shell. This means fusion is taking place closer to the surface of the star and leads to increased reaction rates then before. This produces enough energy to increase the star's luminosity by a factor of 1,000--10,000. The temperature of the star goes down because the star balloons out with this increased reaction rate, meaning the energy is distributed over a larger area. Hence, you get a bright, cooler star.
A red giant star.
Cool red giant stars are located in the upper right corner of the Hertzsprung-Russell diagram, where they are both cool (low temperature) and bright (high luminosity). These stars have evolved from main sequence stars and are in a late stage of stellar evolution.
Supergiants have relatively low temperatures compared to smaller stars like the Sun. Their surface temperatures typically range from 3,500 to 5,000 K. Despite their enormous size, they appear red or orange.
A red supergiant is the largest type of star by volume, but not by mass. It is also one of the"coolest" active stars. These stars have fused most of their hydrogen to helium, and pressure from its core have swelled its size, to between 200 and 800 times the diameter of our Sun. Since the mass has not increased with the volume, the star's average density is comparatively low.
The red giants are very bright and have a relatively low temperature, but they are still red hot, that's why they glow red and not white. Have a look at Betelgeuse or Aldebaran in binoculars, or Antares if you get a chance in the summer, and compare them with a white star like Rigel or Vega.
One of two groups of stars on the Hertzsprung -Russell diagram that have a different set of properties than the main sequence stars; bright, low-temperature giant stars that are enormously bright for their temperature.
One of two groups of stars on the Hertzsprung -Russell diagram that have a different set of properties than the main sequence stars; bright, low-temperature giant stars that are enormously bright for their temperature.
A red color, in a star, is associated with a low surface temperature.
2000 to 4000 kelvin
A red giant star.
Absolute magnitude: they are extremely bright. Temperature: their surface temperature is fairly low.
white dwarf if it has low mass Neutron star or Blackhole if it is massive enough to cause a red super giant
Cool red giant stars are located in the upper right corner of the Hertzsprung-Russell diagram, where they are both cool (low temperature) and bright (high luminosity). These stars have evolved from main sequence stars and are in a late stage of stellar evolution.
The red giants like Betelgeuse and Antares are bright and - relatively - cool.
The red giants like Betelgeuse and Antares are bright and - relatively - cool.
it is a very large star of high luminosity and low surface temperature.....=)))))
Super conductor will have zero resistance or zero resistivity. This happens when the temperature of the conductor reaches a very low temperature known as critical super conducting transition temperature. In case of mercury it will be 4.2K.