天体物理概论2.ppt

1、3. Matter SiO2; CH4; H2O; NH3 etc.,the origin of dust: Cool atmospheres of evolved stars; Metal-rich ejecta of SNe Smoking quasars (Elvis+00)?,3. 6. The Cosmic Rays,Victor Hess (1912): an electrometer discharges more quickly at higher altitudes the source of the discharge must be from above the atmo

2、sphere, instead of the earth 1936, Nobel Prize for physics,19,cosmic ray composite: 98%: nucleons: H+(87%); He2+(12%); Zz+(1%) 2%: e-/+,cosmic ray energy spectrum: J(E)=KE-G,3. 7. Black Body Radiation,Deviation of the Planck-Function: the probability of finding a particle in any given state depends

3、on the statistical weight 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 reflected. Objects that do not absorb all incident radiation are called grey bodies.,24,It is the reflected light that allow

4、s us to see planets, comets, . dust grains. .absorbed light that heats .,homework,25,An apparent magnitude of a star is V=1m.95. Determine its flux density in units of erg s-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 leff(

5、V) = 5450A and leff(B)= 4380A. The zero points are ZPn(V) = ZPl(V) = 0, ZPn(B) = -0m.120, and ZPl(B) = -0m.601. Also useful are the relations between flux density and magnitude: mn= -2.5logfn-48.598-ZPn. and ml= -2.5logfl-21.100-ZPl. 2. An MOIII star is measured to have B=8m.76 and V=7m.09. Please estimate the distance to the star. *The intrin