The appearance of the great range of brightnesn /rv,g+gfn1 eg5q rk*s among stars is due to

  The absolute luminosity for most stars depxcx2 -kdy ,/fxeyj707lva n3 kends on the

  Four different main-sequence stars are colored blue, orangz2id8( 4erz i3s2gy b ccjd44ue, red, and yellow. What is their rank from coolest to hotteczr 2dcs gdz 44uij(e34yib82st?

  A Hertzsprung-Russell diagram8m a5f 2 ipkc2q+h4kzn shows stars on a plot of

  A white dwarf star wq4 c;z:(zi jt5g(g;stm 3clcxith a mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which a star wiley1 6jm2(r b4:j/a xrd i;lfrkl collapse into a whit(bi rr4am er xy jfl21kj;:/d6e dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to always rei.n gk ;/c1av+g)fj7wu rc/omsult in

  Black holes

  Pulsars are rapidly spinnin tj9mqko3 ,-;1ujm 2l-jfpl5gs/ qiuqg

State Einstein's principle o2 m(fpyd+xsg3 (u5letf equivalence.

  The Schwarzschild radius of a black hole is thk(1)bh) q q zeh21pwipat radial distance from the center of a sphere within which not even light can escape. It was first discovered mahbpi k1p 2qq1hz ew)()thematically 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 visible, andl2gr.* fjb g9a the source is moving away from r*a2b9gl.f jgus, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds tonkwm,7ol b 7zoa5/dcsald l51g im*:* a temperature of about

  The Sun has apparent brightness 7c 2.5tr;c mfqr55hn0j numtp at Earth ($1.5 \times 10^{8} \; km$ 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 luminosity equal kb 5)(kl+)rzmrcbzbne ;pi0;9s 2 rnito 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 a meb(hbqa1,n24ocv s0 t lan 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 hasjhmh4y:x 94zug(tsx, 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 ly? (1 ly = $9.46 \times 10^{15} \; m$)

  What is the parallax8mrs5bf5 s 2)lu jypv) angle for Proxima Centauri, which is Earth's nearest star at 4.3 ly s)5j5 fmuy2s 8lvb)pr?

  The apparent brightness of a star i /1dm:h id.nd-)ux( h8i x:hg.yap thhs $1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approximate age of thenhj 8jr 7d36b8qhflx 9 universe is 1/H, where H is the Hubble constant. Taking H =78jx bhrhdlnjf86 9 q3 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of t-81en.pr (d:yt adg elni; c(xhe speed of light, how far away is it fro1-8 (n.p crg;:(eatxn e ldiydm us?

  Estimate the speed of a galaxy that is 10 billion light-yearj 0qguz l8/ :/d.stg z/;qfuqys away.

  Estimate the observed wavelength for the 656 nm line in vxcf ld+f npla :a ,;7z*l/nr+the spectrum of a star which is 100 million light-yeavl l +/7;fcarxnf:,*+n pzd alrs from us.

  About 1 ms after the Big ,u24p qi7//e ( (bjafdpjecc7u) evsaBang, the temperature of the universe was about 1013 K. What energy (in eV) does this correspaeu(i psevf7 eaud)q42/,j /jcc7bp(ond to?