The appearance of the great range of brightness among s* 9mim,bwm:kej 6rbd- tars is due to

  The absolute luminosity for most stars depends o8g:uf *t t)+dvmh*zopn the

  Four different main-sequence stars are colored blue, orange, red, and yellvxy3xx+ dqpn nu +vc6*e (5g: 4l:;0eeuuzyokow. What is 3n :6z;0cx+vuenep duyeo4kxyq +xgu(:*l 5v their rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars f ,tpw*wnf *suy( h)6s;rl-inon a plot of

  A white dwarf star with a masbfa )5kn qqq1io31jhw :x8g i(s equal to that of the Sun is about the size of

  The Chandrasekhar limit o p4b0gg: ox*sqf stellar mass (below which a star will collapse into a white dwa oxgpb*4:qs g0rf) is, if the mass of our Sun is M, about

  Supernovas are thoughto/8xyu5h) rsx1e6 ugp to always result in

  Black holes

  Pulsars are rapidly spiylsyu:qy sc n crtae-;i,f 7)2;- ye:unning

State Einstein's principle of equivxab+(;n y09v lod,k jsalence.

  The Schwarzschild radius of a black holehu5 lon4m93 dk is that radial distance 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'5klod 9nm4u3hs 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 visiblarzb 9ea736ca:z4 vepe, and the source is moving away from us, the color of the light appears to us to be shifted towarbp:aaacze r463z7 e v9d the

  The cosmic background radiation correscchl l4:4w/auponds to a temperature of about

  The Sun has apparent brightness /u-kh.v bp l.fat 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 that of 1w tq ai5tp6k5the 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 mea* yd3g 4aqp1v.j2r doen 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 2, rvj( *la s r6phiak*vamu45a 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 Ce(zc(g.(dw 1ct7f mk zhntauri, which is Earth's nearest star at 4.3 wfzt(.cmh1(d( ckzg7 ly?

  The apparent brightness of a star-a59 pjmjv9h + izmen: 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 approxii *iol/pm/ws 1mate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in * /1im io/pwlsyears.

  If a galaxy is moving away from us at 1.08v::.c(6iv kltqyx72qixhmn % of the speed of light, how far away is it fr :7 hkxiy: .8lmxv q2qcnti(6vom us?

  Estimate the speed of a galaxy that is 10 billion light-(0ij k2x5v m1ef elj1zyears away.

  Estimate the observed wavelength for the 656 nm line in the spectrum of a sthlo k-2fk dkoej))p7.ar which is 100 million light-years k27dke)) ljo .fokph -from us.

  About 1 ms after the Big Bang, the temperature of the universe was 1dd;y4k9s zb yabout 1013 K. What eyd9; 4dsy1bzknergy (in eV) does this correspond to?