The appearance of the great range saiy.*j)m ys6 ie*qa0of brightness among stars is due to

  The absolute luminosity for jx5xc;.-4q+tv -ah s*ydbtd v/hb aq9most stars depends on the

  Four different main-sequeqk8 :q; mo5j ume:2xqsnce stars are colored blue, orange, red, and yellow. What is their rank from coolest to ho oq uem2xjsqm;85:k:qttest?

  A Hertzsprung-Russell diagram shows stars onv0yfse/ieh;ku iu pm0-x 31l2 a plot of

  A white dwarf star with aoxrqnd:; (:*s,e fi cs mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below whicg+vj fv0x5 v;to3m(wh h a star will collapse into a tvm53w+(v0vhx gf; o jwhite dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to always resul+ix97lrodg4 f6 o1 hqjn i4gt/t in

  Black holes

  Pulsars are rapidly spinninl- bl tus ,h+6dyy:7lcg

State Einstein's principle of equivalence.7zkzp nw(e2rsd0 h* z2 -x9cja

  The Schwarzschild radius of a black hcb1q vx )cm7puykl.so 1ne6x g4/3u2 aole is that radial distance from the center of a sphere within which not even light can escape. It was fia7 x /24egck1)lbnqu1cm uv3o6syxp . rst discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can be calculated from a star's mass M as: $R = 2GM/c^2$. Take the radius of both stars A and B as the Schwarzschild radius. If the mass of star A is twice as much as the mass of star B, the average density of star A, compared to star B will be

  When a distant source emits light of a particular wavelength in the gcu/s 6pmr-e ,isy-u(2n: hpkvisible, and the source is moving a-ugy sc/ :n hr6uesip2 (-pm,kway from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiatif1ixu :0vzeh+ on corresponds to a temperature of about

  The Sun has apparent brightness at Eadg dd y:7xxo0+54eubu 3mz +aemd0l (prth ($1.5 \times 10^{8} \; km$ away) of B. What would be the apparent brightness of the Sun at Pluto, which is $6.0 \times 10^{9} \; km$ from the Sun?

  A star has absolute lu f)zzg k4p-ia3;)j.qn v3usivminosity equal to that of the Sun ($1.5 \times 10^{8} \; km$ from the Earth) but is 10 pc away from the Earth. By what factor will it appear dimmer than the Sun?

  The Earth's orbit has bnl6s-qg ++ ahuwl0rk60*zd mxt4oj - a mean radius of $1.5 \times 10^{8} \; km$. Over a six-month period, the apparent position of a particular star varies by $0.00014^{\circ}$ due to parallax. How distant is the star, in km?

  The Earth's orbit has a mean radius okd.x0b+)zlf5 wpf,q c)gp g/xf $1.5 \times 10^{8} \; km$. Over a six-month period, the apparent position of a particular star varies by $0.00014^{\circ}$ due to parallax. How distant is the star, in ly? (1 ly = $9.46 \times 10^{15} \; m$)

  What is the parallax anglu4clr xhwm 4sl-2rbrz 41 (w,he for Proxima Centauri, which is Earth's nearest star at 4.3 lyr14xlhwb-whzs2r ,l(ru44cm ?

  The apparent brightness of a star is uv20c p9z.ba plh+r;j3l dw *b$1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that 0pt i-zo (jq9wd0zebu uy7ri: xm 1-l7the approximate age of the universe is 1/H, where H is the Hubble constant. Tak7jl m:zqdz-r0iy 7wux(-pu o910ie tb ing H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of i3g2(1dn2wkj etcrjl)vf74d the speed of light, how far away is it from us?w4d (1lj3k ej rcg2fi2)d nv7t

  Estimate the speed of a galaxy tba09 izq z(l8d)u4psrhat is 10 billion light-years away.

  Estimate the observed wavelength uhj5(/gqv mlmca -0gue-m3 /ffor the 656 nm line in the spectrum of a star which is 100 million light-years fromu gumf0cm-5a /mgv(hel/jq -3 us.

  About 1 ms after the Big Bang, the t c0h /ovyms f9l1s2+flemperature of the universe was about 1013 K. What en chfsll+m0/2o fvs y91ergy (in eV) does this correspond to?