[填空题]
1.VV Cephei is a binary star system composed ofztzvsj4z8ngrn+k+7* /me.v7tg u :e v two stars referred to as VV Cephg*/7 zmung4krje7n:e tv v +vz8z.st+i*jyqc dql5 ,0o 7f8gyei A and Vg l8yyq 0 ,qioc75d*fjV Cephei B.
(1)The measured wavelength of the peak spectral line of VV Cephei A is 760 nm. Show that the surface temperature of VV Cephei A is approximately 3800 K. T = K
(2)The surface temperature of the Sun is $T_⊙$=5800 K. The luminosity of the VV Cephei A is $2.7\times10^5$ times the Sun's luminosity $L_⊙$. Determine the radius of VV Cephei A in terms of the Sun's radius $R_⊙$. R = $R_⊙$
3.A Herzsprung-Russel (HR) diagram is shown.
Plot the current position of VV Cephei A on the HR diagram and identify the classification of VV Cephei A.
2.The mass of VV Cephei B is about 11 times the mass of the Sun and it is not on the main sequence.
(1)In terms of forces, explain the condition that causes a star to first leave the main sequence.2
(2)Explain why VV Cephei B is likely to remain on the main sequence for a shorter time than the Sun.2
(3)The parallax angle for VV Cephei B is 0.31 arcseconds. Calculate, in light years, the distance between the earth and VV Cephei B.2. d = ly
(4)State why the parallax method is not suitable for measuring the distance of very distant stars.
