Sun
Videos
The Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surf
The Sun as viewed through a clear solar filter
The photosphere is structured by convection cells referred to as granules.
The Sun's transition region taken by Hinode's Solar Optical Telescope
During a total solar eclipse the solar corona can be seen with the naked eye.
Red giant
Videos
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature
Sun
…its core will undergo a marked increase in density and temperature which will cause its outer layers to expand, eventually transforming the Sun into a red giant. After the red giant phase, models suggest the Sun will shed its outer layers and become a dense type of cooling star (a white dwarf), and no longer…
An illustration comparing the structure of the Sun (left) and its possible future as a red giant (right; not to scale, this image is of a false color for more contrast and does not depict stellar mass loss and the asymmetry of a red giant and the Sun is actually beige-white; an actual red giant would be orange-white to human eyes). The inset at the bottom right shows a size comparison.
This image tracks the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant on the right after billions of years
Mira A is an old star, already shedding its outer layers into space