On an hr diagram, a red giant has lower luminosity than a white dwarf. true false

FALSE

Explanation:

   White Dwarf is the name given to a type of star much smaller than ordinary stars and with a small brightness compared to the others. It represents the stage after the death of a star that was not massive enough to become a supernova, and eventually turned into a planetary nebula.

    Less massive stars like our sun, for example, by consuming all the hydrogen from their nucleus into heavier materials (such as carbon) can become a type of star known as the Red Giants, made up of a small nucleus. very dense carbon and more diffuse outer layers where there is still helium and hydrogen in fusion.

    But these red giants are not big enough to produce the necessary heat and continue to fuse the core material into an even denser one. Even so, the core size continues to shrink. In this way, the density and pressure in the core increases more and more. When it is no longer possible for the nucleus to shrink, it stabilizes at a density of approximately 1010 kg / m³, but the outermost part of the star continues to release energy and consume helium. This outermost layer becomes unstable with increasing radiation and dramatically increases in size at a speed of tens of km / s, transforming into a huge cloud made up of materials that once made up the original star and fusion products.

    Right now, the former red giant is now two different things: a huge diffuse cold cloud called the planetary nebula and a small celestial body made up of a carbon nucleus and some helium and hydrogen melting in the crust. This heavenly body is called the White Dwarf.