The appearance of the great range of brightness t2t8 )h/3iui2f(t sahuwu /lo among stars is due to

  The absolute luminosity f: ik1z eeg /ayv9.a28pth7 acjor most stars depends on the

  Four different main-sequence sxnbl l;:kppv6qn ;lf jq8 3s5y9 v)oj*b;5a latars are colored blue, orange, red, and yellow. What is p v )qx9s la5ajlk5jbb*ofvy;:nll 68; n3p;q their rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on a pat;-u *zoz qy5j +mnro8mxe-t:*u 5uklot of

  A white dwarf star with a mass equal to that of the Sun is about the size o)m l7o 3-yelwz y,f-i2fkm8uff

  The Chandrasekhar limit of stellar mass (below which a star will collapsew yfvfnj fx8c:o3nf7-o)+ 7axjf:gu, into a white dwarf) is, if tvjwf-8f fgxf) n:7uf ,a3y x:+ooj7n che mass of our Sun is M, about

  Supernovas are thought to always racug z/x1z x59esult in

  Black holes

  Pulsars are rapidly spinninu .a4gj aqk8 45vuho*ue.v);zkss km)g

State Einstein's principle ofn w5 ygd 4/.m-s,kugvs equivalence.

  The Schwarzschild radius of a black hole is that radoo.gk5(kc0 mv ial distance from the center of a sphere within which not even lkko5cv( mg0o. ight 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 wavel40m.i b/nh d,ton ec,eength in the visible, and the source is moving away from us, the color of the light appears to us h/ 0td .,4 i,ocebnenmto be shifted toward the

  The cosmic background radiation corresponds to 85ouj 9+ n t pgfi8d6t0osj+lia temperature of about

  The Sun has apparent brightness at Earl oo+n2hhj+wv+w 6+qc *pmt*nth ($1.5 \times 10^{8} \; km$ 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 om5)eykapvt tbfi4 467x fh42zf 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 hab.hx/ik0 )q hmee-yi. chrw46s a 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 km?

  The Earth's orbit has a mean ra 4 dm:/t 9hw4m)j7xih8k dqftadius 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 nea0j+w)ljewu* u rest star at 4 0uj*j+lwew)u .3 ly?

  The apparent brightness of a star is ot2n8 otw swz6(ohpl9 0)mes /56g yfxnrjx.)$1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the apprx*agpyz:0l/qu rou2p p x*1t7oximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age qp/ x7gl0p:t2ouapu*1ryz *xof the universe, in years.

  If a galaxy is moving away from us an)u mh+vx9 6uj5lwnhie v6 8z9t 1.0% of the speed of light, how far away is it from ujm 9)iwx6lvunhnz 596 vhe8 +us?

  Estimate the speed of a gala8 6hb-toagrhaq .a/)e *o8 svuxy that is 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm line in tejfv/w ndmh1 + r;3a3dhe spectrum of a star which is 100 mi 3vrd3w mn+ef1jhad; /llion light-years from us.

  About 1 ms after the Bysu405tb )uli r/ 6 p-;rntuhpig Bang, the temperature of the universe was about 1013 K. Whs b)4nitr yu/;pt6r5- h p0uulat energy (in eV) does this correspond to?