The appearance of the great range of brightness among starjaf1oyx ns7wa) 0*f7( zhwxf9s is due to

  The absolute luminosity for most stars depen q.k(a7)z- x/jgsntk. hk t)pnds on the

  Four different main-sequence stars are colored blue,ebrawb ;) /7qh. gy4la orange, red, and yellow. What is their rank fry b ;ahw qbeg/r47)al.om coolest to hottest?

  A Hertzsprung-Russell diagram0uiqu;d 6 oume,5baz* shows stars on a plot of

  A white dwarf star wk:v+hkt 1o6 vgith a mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (vxayqq l(3e u qd3y/ 23saiv 36psb/(gbelow which a star will collapse into a white dwarf) is, if the mupa(/y3gbi3v36 d( 3ysasx q qqv 2el/ass of our Sun is M, about

  Supernovas are thought to always re0s ,7 yet5r/q aewy(hyn,h:2;l coqmxsult in

  Black holes

  Pulsars are rapidly spinninawh+hhbzkfh69) nuo.k:8 hw .g

State Einstein's principle of equivalekfq9b+lodg:bw0* :b58qws c p nce.

  The Schwarzschild radius of a black hole is that radial distance from the centeyz x bh873a9b9n9eqec r 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 fy9b3b z xqnc9h8e7a9erom 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 vi ;zuhn ek1uv) 0,wiepqbp*7; esible, and the source is moving away from us, the color of the light appears to us to be shifted townpizp,;)h;e 7vkwqe u* 0 1beuard the

  The cosmic background radiation corresponds to a y4xr; o3l fq6ptemperature of about

  The Sun has apparent brightness axm5+g t*q;clsk llnl50(r 2bj:e8zn kt 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 equactl.pq3 g.u7vwq 8ptw9kn wfx 4( 6dz:l 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 a meaq :jii. ii ya0d/,iwm*n 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 - )5mu37oiivl/jeqkg 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 s5vcv 2z ka3:aw.0 :kab71 ,wsis kficEarth's nearest star at 4.3 lyf, zack0s2:wsikk3i5v w b 1cva:as7.?

  The apparent brightness of a starrreg 9l/9l; b8zu8rabf p5 6nc 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 aptx g4cb ga(ysq3g,/d 3proximate age of the universe is 1/H, where H is the Hubble constang4qbx3ya,s/ d (g3tcgt. Taking 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 the speed of lub b/85 nwyx;ujz1x4:6bo o2xl qqht(ight, how far away is it from usxb 5 q4z2 n/tuh1xb6ob;o(8 wujlx :qy?

  Estimate the speed of a galaxy that is 10 billion light-years xyb j6)ya6 5nzaway.

  Estimate the observed wavelzq5m9qycd6; 3lrdr n c eykz7;0vg0 z8ai (-znength for the 656 nm line in the spectrum of a star which is 100 milliom-zn izq;r7;z085cd93 g dlrc6q(nye ky0v azn light-years from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 10l8f-yfk f2 xe113 K. What energy (f-yf efx8l2 k1in eV) does this correspond to?