The appearance of the great range of brightness among starsb9lclb e7h)ok h g,og*1+r/rt is due to

  The absolute luminosits,dw8a i(mo 5gy for most stars depends on the

  Four different main-sequence stars are colored blue, n.f,8r(nubg x9yq8hn orange, red, and yellow. What is their rank gfnh8,n.89b(yr nq x ufrom coolest to hottest?

  A Hertzsprung-Russell diagram show g 4l:;l (pbypvx7kpb/p h*/bgs stars on a plot of

  A white dwarf star with c c;w9z,fl yl54k/1buhx8b pya mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which a stay zsx-efx9.nuce;8tx ncfiq7- y8 3m-l b8 6nlr will collapse into a white dwarf) is, if the mass of our Sun is M, aboulq s8 tm-i9 nzcxf- cxxen-uef ;3y8nyl6 7b8.t

  Supernovas are thought to always result i63nuji- nj7q vn

  Black holes

  Pulsars are rapidly 5yq3j,d.d*dr97ywzdzvdg wrqf37:pspinning

State Einstein's principtah* */e7 :jz nrw0ij u4zpz;ule of equivalence.

  The Schwarzschild radius ox fayiy(( 1y)of a black hole is that radial distance from the center of a sphere within which not ey1ix)y(f ao(y ven 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 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 hsd- (d.doaf3in the visible, and the source is moving away from usd3da-f h s.(do, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a b0-jnarr3.m9k l sn6rtemperature of about

  The Sun has apparent brightness at Earxu44lk ;t q )83 yd0p:flcggdyth ($1.5 \times 10^{8} \; km$ 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 equnwe3ihs(5m p .al 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 mean radz(tuqsdvt6 .7.by 0ec/gi(hnd )ie. e ius 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 eq (papa,o-3uj oyny96t 8wv9of $1.5 \times 10^{8} \; km$. 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 Centay:crt,6 :hfzpuri, which is Earth's nearest star at z,: 6tc y:rpfh4.3 ly?

  The apparent brightness sdi9agb.rw m3-d1sx0 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 the o +(zm **fx.jf zsvu)zuniverse is 1/H, where H is the Hubble constant. Taking H = (zf v* f.)z*xuzmsj o+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 light, how fec+geg9 7tbwi2* 0bmmar away is it from uscig* +gw09 mme2ebtb7?

  Estimate the speed o0 ds;tnx)9 htxf a galaxy that is 10 billion light-years away.

  Estimate the observed wavelength ft++w m9 :lupm1r gpid;or the 656 nm line in the spectrum of a star which is 100 million lightirt+;+ ppm :l9ugd1m w-years from us.

  About 1 ms after the Big Bank k hgdq9v96l.cx)6ssg, the temperature of the universe was about 1013 K. What energy 9).ds s lhxqgkvk 66c9(in eV) does this correspond to?