E 2.1: State that fusion is the main energy source of stars
E 2.2 Explain that, in a stable star (e.g. our sun), there is an equilibrium between radiation pressure and gravitational pressure:
Like any other stars, the sun is stable because there is an equilibrium between the outward pressure and the inward gravitational force. The outward radiation is the heat generated during fusion and is calculated by E=mc2 and the inward force is the mass of the star.
Luminosity (L) is the total power radiated by the star or the energy emitted per unit time. It has a SI unit of watts. Luminosity depends on both the surface temperature and the radius or surface area of the star. If the radius of two stars are the same then the star with the highest temperature will have the greatest luminosity. If the temperature of two stars is the same then the one with the highest radius will have the greatest luminosity.
E 2.4. Define apparent brightness and state how it is measured
Apparent Brightness is the power incident on earth, perpendicular to unit area. It is measured using this equation:
No comments:
Post a Comment