The appearance of the great range of brightness as4-/xopbnd3/d h.-t 4 n vikuzxey- z2mong stars is due to

  The absolute luminosity for most stars depends oexunkl2+q 5ph; -y0zsn the

  Four different main-s 2 xewu8 r9y;/3wuzuluequence stars are colored blue, orange, red, and yellow. What is their rank from coolest to hulw;e3zxuw2 9y /uu8 rottest?

  A Hertzsprung-Russell diagram shows stars on a plogkkdqp zw) dig 5q)-)2tyeb;qhv s+/3t of

  A white dwarf star with a mass equnsk hyt ps, -b645nkz 0e)0poqal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (belowxk3k7aq9hp- x which a star will collapse into a-3x kq79a xhpk white dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to always resus2ar5 p9k8ncj 6l:v-x31fi7 o kxngytlt in

  Black holes

  Pulsars are rapidly sp,ys d 0deiql54q b9ka*inning

State Einstein's principle of equivalencet7z(-9ov) z9 f 9* ylfpbqfjgo.

  The Schwarzschild radius of a black hole is that radial distance fromd wrr4 5xgukj i*)jc9tt/4w;v the center of a sphere within which not even 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 a; cv59g j) *xirk44wujdttrw/s: $R = 2GM/c^2$. 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 the visible, andjx)*go qg2r*wet5)7n -a xfht the source is moving2f5 )g) *qxgot7natxwj hre *- away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds lv,u a)zz(tqj2eh*.d to a temperature of about

  The Sun has apparent brighqn8 cdb, rv1o)qk-iba9b g5s2tness 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 eq0 usydtk 1-zsxu9, .equal 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 radimxiu5 7a;xck8us 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 mdu/lna6ajs2r c34n s 8b.ehn5ean 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 ly? (1 ly = $9.46 \times 10^{15} \; m$)

  What is the parallax angle for Proxima Centaurief h)6n+f8hnre0or(l 6y vv/ x, which is Earth's nearest star at yl8x non/hv er6)v h0+(6erf f4.3 ly?

  The apparent brightnes r 8-e:8yokbgns 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 thrwxw:b9e; dbut6t(09rpey h c0oo (.oe approximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimat. ww;erud9p6e:(h09bo (bo ty xco0tr e the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of the speed of lighgqva9fk x1i 6 d.a(4nmmr2kg-t, how far away is it fr 4gr -x9gqm(2 aak6v if.kndm1om us?

  Estimate the speed of a galaxy that is 10 billion light-y bga :g./ v;0e5w8) qqsz4sa2vd shvnla9cq7fears away.

  Estimate the observed wavelength for ks od:55/w6 uau;6ir sr57f ykud-gznthe 656 nm line in the spectrum of a star which is 100 million light-years from us5wai/s76z5 ugr-uu:sfk ;n 6 ydr 5kod.

  About 1 ms after the Big Bang, y/s (cn( ;(xysmxowmy wm86 8gthe temperature of the universe was about 1013 K. What energy (in eV) does thnmgmow8s yx8x(m( ;ywcs/(y6 is correspond to?