They would shine only with reflected sunlight. Very few of the hydrogen's electrons are in the ground state. Nuclear fusion has depleted the solar hydrogen. The low pressure of the Sun turns the absorption lines into emission lines. Most giant stars are drawn to the core of our galaxy.
Few stars form first as giants rather than main sequence stars.
They have small masses and high luminosities. Part B B1. List the planets in order of increasing mean distance from the Sun and indicate which are terrestrial and which are Jovian planets. In the context of how the Solar System formed, give a plausible explanation for the fact that Jovian planets are larger than terrestrial planets and for the fact that Jupiter is larger than the other Jovian planets. Make a sketch of a comet.