The appearance of the great range of brightness among stars is d-hdk;f t8a lw6ue to

  The absolute luminosity for most stars depends onvop v;w 3gv.cau5*+pp the

  Four different main-sequence stars are colored blue, orange, red, and yellow. *l,u;u q-qbxnWhat is their rank from coou-ul x bq,*qn;lest to hottest?

  A Hertzsprung-Russell diagram sc +1t:l+lmu rjp p oin6s(hv44hows stars on a plot of

  A white dwarf star with a mass equal 9qnx t.f: v y7,u5gk k(vzjxh2to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which akr h5zjw7iyht:1 /5wc star will collapse into a white dwarf) is, if the m:r7 zk1h/5iw5hy twjc ass of our Sun is M, about

  Supernovas are thought to alwam(h gnt/isfo:(8 8 9jroue 0siys result in

  Black holes

  Pulsars are rapidly s* td2+bsekb ;cpinning

State Einstein's principle of xhz8hv63ef8a (wb 4iu equivalence.

  The Schwarzschild radius of a bu(zbl53 jfo0h lack hole is that radial distance from the center of a sphere within which not even light can esczb l(h5u03fojape. It was first discovered mathematically 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 wav)-jt nsl19l/;nn) hre +hq kd ahnv3-belength in the visible, and the source is moving away dh1h l-lkjn )r/-h bn n)q+svn ;et9a3from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperatgm1lrp . sy118o4psbcure of about

  The Sun has apparent brightness at Earth xmk)w-o 1m:blulq4 s(($1.5 \times 10^{8} \; km$ 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 ofnsf;rnm (.d;y 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 o+7 vgj.8p mtvab,mai*yst 34mean 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 mean radiujdn cuhe)j7 *v2 g,.mos 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 nearestgqk)z d *9 6(yua:k:1epymm bp star at 4.3 mq g)p* ybzdk61ekyu(a9mp ::ly?

  The apparent brightness of amb w2. h)i),a w cqzjr ::oirjd,(x+bl 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 the universe is 1/H, whe :fvswb*c2 0o8ea3l xzre H is the Hubble constana*eo v csw b:f30l8z2xt. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from +i..od 3by ;:d+v s+* 0ujidqblvu; r;iihiy ous at 1.0% of the speed of light, how far away isds0u vhqir+oulj+. *;v3y:iodyb+i; ib.i ;d it from us?

  Estimate the speed of a galaxy that is 10 b()7eg4*p-zzavvjr bo; dp )riillion light-years away.

  Estimate the observed wavelength for the 656 nm v/9yr yzb/m,r5q6 kwhs+m5va line in the spectrum of a star which is 6vzvr5/ bwa rh sq,/5my9+kmy 100 million light-years from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 1013 gi,fz*gs/ j3yg c mz29K. is/z9gj,23mfg gz yc* What energy (in eV) does this correspond to?