1、 3. Matter 1057.7,4)(4 4431544 aTuPKe r gc maaTTcTBcu rad Radiation pressure is a strong function of temperature. negligible for low mass cool stars; very important for high mass hot stars, e.g. WR. 3. 8. Grey Bodies Black bodies: absorb all incident radiation. Albedo: the fraction of light that is
2、reflected. Objects that do not absorb all incident radiation are called grey bodies. 24 It is the reflected light that allows us to see planets, comets, . dust grains. .absorbed light that heats . homework 25 1. An apparent magnitude of a star is V=1m.95. Determine its flux density in units of erg s
3、-1 cm-2 A-1 and erg s-1 cm-2 Hz-1. Do the same conversion for B=1m.95. *The effective wavelengths of the V and B bands are eff(V) = 5450A and eff(B)= 4380A. The zero points are ZP(V) = ZP(V) = 0, ZP(B) = -0m.120, and ZP(B) = -0m.601. Also useful are the relations between flux density and magnitude: m= -2.5logf-48.598-ZP. and m= -2.5logf-21.100-ZP. 2. An MOIII star is measured to have B=8m.76 and V=7m.09. Please estimate the distance to the star. *The intrinsic color of MOIII stars is (B-V)0=1m.57, and th absolute magnitude is MV=-0m.2.
