The appearance of the great range of brightz (j y8qqg5jl/s vhwds ms4090ness among stars is due to

  The absolute luminosity forqc0htu7;i qq55 q+)smvkb/ de most stars depends on the

  Four different main-sequence stars are colored blue, orange, -updkn2;7 y pbred, and yellow. What is their rank k-y;7p2bn du pfrom coolest to hottest?

  A Hertzsprung-Russell diagram shows sta0h ;kikjhn89z xoq47srs on a plot of

  A white dwarf star with a mass equal to that of t(lpmy.iqv 5t *he Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which cd,ncku*- :h9hhjy3y g 5mxm(a star will collapse into a white dwarf) is, if tc3h-y g5mkn u,cmd:9xhh(*jy he mass of our Sun is M, about

  Supernovas are thought to always xon.9ci2/ nk ) kocii.result in

  Black holes

  Pulsars are rapidly spa.0pr yorm o8-inning

State Einstein's principle of equivalez4bwy rhw:syg 0s05npqmn) - 4nce.

  The Schwarzschild radius of a black hole is thf vo1. q/bp7hvr r;*rbat radial distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 191 obr vfhpb*/rq7;1 .rv6 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 in phr9)d 2 cxqsjs(; cz*the visible, and the source is moving away from ussc2ds9rp c*qxhz; )(j , the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds t i-qd ((v6b hjongi1h7o a temperature of about

  The Sun has apparent briga176w r lqymmq-3 z9edhtness 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 Sunkl nut jh:h:k-3 ppf/*d,6 dx44zrbtb ($1.5 \times 10^{8} \; km$ 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 h3dvnw3)qp.x i uose o/x(j53radius 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 o88zbo k s4q6kwf $1.5 \times 10^{8} \; km$. 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 angyhlsp-0h 3g.c9+m l xu pv8ew1le for Proxima Centauri, which is Earth's nearest star aty19l.vmexu0gh- wsl83 ph+pc 4.3 ly?

  The apparent brightness+o iuz*o5q1 2xap)pem 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 universe is 1ojl852f6s(-b y yg jud/H, where H is the Hu(jb u oj2l-6yyd8 s5fgbble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away s9a).l-oz:yrvxid kv,h j w -.from us at 1.0% of the speed of light, how far away is it froajsvd ,kwo.9z x.y-v -)h:irlm us?

  Estimate the speed of a galaxy that is 10 billion e .cc.j q(if)o sqxckf+.f-y5light-years away.

  Estimate the observed wavelength for the 656 nm line in the spebc zk5-ypl o x7hl;1f(d 9+ipwctrum of a star which is 100 million light-yea9 hdy;p(1+xlcp5kf blo-z7w irs from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 101)7ez abj,oicdis0h l.b 8- c2x3 K. W 8e ,xsia. d0hb-zlb7io)j2cchat energy (in eV) does this correspond to?