The appearance of the great range of brigta3 grf qb11o*8.g3 +fu jtllghtness among stars is due to

  The absolute luminosity for most stars depenhz-5+nu, grr p s-76xhlc csg,ivb xc11 9-kxwds on the

  Four different main-sequence stars are colored blue, orange, red, and yecp4z j0c8xq 9 qv4rab9so1/ jsllow. What is thesa1jb0c/ c4v8prxq9s49q oj zir rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on a plot oir9w/q1hdua gwd su( lg7k : d+)05vhnf

  A white dwarf star with a mass equal to that of the Sun is about the size ot2y8tvlu62l,3 mncy;gl4 rqf f

  The Chandrasekhar limit of stellar mass (below which a star windq71r 1/x-ooba )ar:i or1v r( yxz3all collapse into a white dwarf) is, ay 1raax-d 1v b/oqz:3r7n1rr)(o xioif the mass of our Sun is M, about

  Supernovas are thought to always resmwit m p/,nzb.xed)5zkn am1i-p2m37ult in

  Black holes

  Pulsars are rapidly q;e7 mdixa(/tdxr w*zcum( (6spinning

State Einstein's priq47hj)3lv chh nciple of equivalence.

  The Schwarzschild radius of a black hole is that radial dis6rw :qn5ev6 y .m3uiljtance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916l ue5m.v:6qwr yin j36 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 particoc3(jcti 3k7i z9fl,+r zmxwi s6ye4y -g5*crular wavelength in the visible, and the source is moving aw 5ri oj7 il*x(it ,gy3kcz 4r- ycmc+z3fesw96ay from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiationyknb h(.f,or w-d(fy3 corresponds to a temperature of about

  The Sun has apparent 5jvqm7t4w1o nzti,)e m2x( sabrightness 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 the)mgsjo5 7/mmh 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 radius of rd 1loz lx,w),:ht6u(lj2oxv $1.5 \times 10^{8} \; km$. 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 rawdau (cs*:ul /( nxfd.dius 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 Centau(; tg8ixh4jxx:g ) etae.l+e iri, which is Earth's nearest star at 4.3+gt8a l.xgx;xt(4i e je)ie h: ly?

  The apparent brightnt3oeq.k+oivtwz8 v/ lw5)h66j qvxv3 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 the univezh aab;p9,d7 y/jbg k.rse is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.ay ;d k7b,pb/hg9zja.

  If a galaxy is moving away from us at 1.0% do8znwa0c 5w( of the speed of light, how far away is it fd oaw5wnc0 z(8rom us?

  Estimate the speed of a galaxy that is 10 billion light*folz y+ . kr/+2fqihq-years away.

  Estimate the observed wavelength f.(apl+e .w b4jxemdd*or the 656 nm line in the spectrum of a star which is 100 l +pm.wab*.4djexe( d million light-years from us.

  About 1 ms after the Big Bang, the temperature of the ukhbv8/i pm0r)g mx/sc5s ( c-kniverse was about 1013 K. What energy (in eV) does this corr/gkvm5 x 0cib/(kpm-8ssc r)hespond to?