The appearance of the great range ip4s r7fjvb5u zz/e48of brightness among stars is due to

  The absolute luminosity for most stars dependtl.x 8;a w,r(rshg ri3s on the

  Four different main-sequenc(a7 mp.el(ea 8ehlm+ ce stars are colored blue, orange, red, and yellow. What is their raneml a8(+ca meh(p7.elk from coolest to hottest?

  A Hertzsprung-Russell diagkr ac p,skk88;ram shows stars on a plot of

  A white dwarf star with a mass equal to that of the Sun is about the siztdd :j/rich4 az2(f ;ke of

  The Chandrasekhar limit of stellar mass (below which a star w (xab/q h) ptkwdtdr9na)05/ xill collapse into a white dwwd xa(/0)pnqxrh)t tb/kd 5a9arf) is, if the mass of our Sun is M, about

  Supernovas are thought to always rwcbi lo53*gx8kvg 5i3 esult in

  Black holes

  Pulsars are rapidly sp 8rtnwiw /d-pqab q1dv6 k.5l9inning

State Einstein's princiz5xu+-ybz- r eple of equivalence.

  The Schwarzschild radius of a black hole is that radial dtkkz)hs ijv2-3nw1 x3vt:( zjistance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can be calculated from a star's masz3:v3whn)kx1v- stikz 2(jtjs 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 imfazv42qa t: 39qzdg6n the visible, and the source is q2t v46adqz9fag:3 zmmoving away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperat cn.z.gnjm2 ,hmfm ,1wure of about

  The Sun has apparent brightnec jrm4 1u6fegtt5z.* w4cae9bss 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 to thhrb.)rc a(i : *as j5)y0iwuefat 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 mean radius of obtw:o 3nfp6g re/3(r$1.5 \times 10^{8} \; km$. 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.i ug4+umpb 6q6b6t h1 uq3xus 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 parallax angle for Proxima Centauri, which is Earth's nearem7v-v hf.p3srq.iz;m st star at -qm7s.ir.;3fvvz mhp4.3 ly?

  The apparent brightness of a sbr e* h9w, n6ldkodiva8,+x d:tar is $1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approximate age of the un,0h rt -w(rajeiverse is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age -r( jaht0we r,of the universe, in years.

  If a galaxy is moving away f nt kp/rg3vtc 3rym*3-rom us at 1.0% of the speed of light, how far away is it from u3 yrp 3/3kn*tgv tr-mcs?

  Estimate the speed of a galaxy that is 10 billion light-years awaet3 v 4pxz.l/(mirg k2y.

  Estimate the observed wavelength for the 6fme8mhgf pdk(0(it o;uk8l29 56 nm line in the spectrum of a star which iso9 mf f8gile8t2h0kp( um;d (k 100 million light-years from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 1013 xs 9uhhi.wo6kut7h13m(z-bz K. What energy (in eV) does this whhi3 b -9sthx(ukuzz67m .1ocorrespond to?