20 1. what will happen to the relative amounts of hydrogen and helium in the sun over the next few billion years? hydrogen increase and helium decrease hydrogen decrease and helium increase hydrogen and helium decrease hydrogen and helium will remain the same 2. for the sun to be stable the inward and outward forces within the sun must be equilibrium part of the fusion reaction focused in the core balanced with temperature and energy 3. a hot, bright star would appear in which section of an h-r diagram? lower left upper right upper left lower right 4. all stars remain on the main sequence until they stabilize for about 90% of their lifetimes until they become protostars for about 10 billion stars 5. all the planets in the solar system have except venus and mercury