The appearance of thea+ae21ef;m p)v vnl 3q great range of brightness among stars is due to

  The absolute luminosity for most y ss77lzkq9 -ostars depends on the

  Four different main-sequence stars are colored bluh7n l *gk mkp+fstvk* ;xhz)tn.e0ks-s* 8ok5e, orange, red, and yellow. What is their rank from coolest to hottk)z*ls-k0 tv*s8h;mxk knsk7*ne fop.5g+ htest?

  A Hertzsprung-Russell diagram 7zssd m01v/ 77qxh1lvog ;rlcshows stars on a plot of

  A white dwarf star with a mass equal to that of the Sun is about tq.u /ku:tupn,ns2 oq/ he size of

  The Chandrasekhar limit of stelkz ,i1crgpea4:d 2lc +lar mass (below which a star will collapse into a white dwarf) is, if the mass of our Sun is M, c2ka:e ,lzr+i 1d4gpc about

  Supernovas are thoughc:vb /oyug.z 2t to always result in

  Black holes

  Pulsars are rapidly if8kf 7zozt::spinning

State Einstein's pri.iy6rj ,ti/ lllf*e1u7 mwx 6pnciple of equivalence.

  The Schwarzschild radius of a black hole is that radiilluy/ hb-yogy5 *9 al/*1sbaal 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 oay*s yh*/1 9biybl/alu l-g5general 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 visrv oj2l(w.(xq hr,4rkible, and the sor v2(xk,or.jwlq( r4 hurce is moving away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation correspondsy6au w,eqy-s. lc+ro c0t 0fe9 to a temperature of about

  The Sun has apparent brightnessqf,lq i 8ip9 t:pkz+0t 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 that of thqi0o ((kj3-ggp2 hqx 0kgfyl6e 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 rad :np9vu a8f 1ezl58lpsius 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 okq8;;p w o+zxeds ogn ;ty*i*4f $1.5 \times 10^{8} \; km$. 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 lm2wuno2e, r1Centauri, which is Earth's nearest star at 4.3 ly?ol2ume,1rn w2

  The apparent brightniyy oi,3,wc1(spisns z28opr;. dp z )ess of a star 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 e5cw qg6 )4v1h0dbkys the universe is 1/H, where H is the Hubble con014k6 qs)cb5hywge vd stant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1)2stl2fp6/ x z9 yjqur.0% of the speed of light, how far away is it from u yp/jlrqf sut6)z922xs?

  Estimate the speed of a galaxy that is 10 billion light-years aw(uz*wt0yfxa,m cc7k4ay.

  Estimate the observed wavelength for the 656 nm line in the sjs gr *b:rjto)ah6):bpectrum of a star which is 100 millioj:6rt)ba *j o):hg sbrn light-years from us.

  About 1 ms after the Big Bang, the temperature of the univers za/d:.g y 4ahnqdd67se was about 1013 K. What energy (in eV) does this cora d/h 6: 4n.dyqsdag7zrespond to?