The appearance of the great range of brightness among stars isl ,fj*tg;6xfy due to

  The absolute luminosity for most stars dep)h8m,;m cve305hv w exnygi rq64ahe9ends on the

  Four different main-sequence stars are colored blue, orange, red,gsyv9u s/j:g6 ;cb/rx and yellow. What is their rank from coolest to h;b9xsr/gsvj c6yg/ :u ottest?

  A Hertzsprung-Russell diagram shows si* o7/y2clqhg0 if1hl.1tc jl tars on a plot of

  A white dwarf star with a mass equal to that ofwm2u oky8-7v ;8 mjwb;w xiqhen):p/r the Sun is about the size of

  The Chandrasekhar limit of stellar mass (bfctctp -dlx /bd/:)r,elow which a star will collapse into a white dwarf) is, if the mass of ourcpld/:dfxt/)tr- cb , Sun is M, about

  Supernovas are thought( 76t7yh6dmg. )wy ujnajx3 kd to always result in

  Black holes

  Pulsars are rapidly soeir:(d9qux ( 5i-*qafye 9iopinning

State Einstein's pri6mw;k1g gd+a 8d0t t ejnfu0.fnciple of equivalence.

  The Schwarzschild radius of a black hole is that radial d0k do0g2uf64x sc:lg g0wbly5 istance from the center of a sphere within which not even light can escape. It was first disc:0g5lf06xsl 0gb4cu wydog2 kovered 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 wavelength5qoxo, hw67ytnv w dl*z.,h0u in the visible, and the source is moving5,t06y7dvxo.uh,zw h*l oqnw away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiatir. 6bd1ateh25nov5 wp1z(wye on corresponds to a temperature of about

  The Sun has apparent b7yp 2i/rt* 9 hnik*+cr1qdrnurightness 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 equadpq1lx8 pptfq65j j uj.k/ t5/l 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 meag u:j+pn7 qfoujhm30; n 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 memp(fbs.+mmy 66qsbo -an 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 angxb p- gicm9wf,6eu8hhh88ni9le for Proxima Centauri, which is Earth's nearest star at 4.3 ly?m npcg f 9i,-8ixhh98eb6w8hu

  The apparent brightness of a so4s/ sy 8t:ouitar 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 approximatqsgv bw ime:1 ,/yc6z+e age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the un1+ vgz by6m:cq we,/isiverse, in years.

  If a galaxy is moving away from us at 1.0% of the sigh7xg7 r3 k3iy4x fb*7wkcc ;peed of light, how far away is it from us?3hkfyi ix wgkc437bc7x 7rg *;

  Estimate the speed of a galab-ufqhcezk w , ;7g* .tk29wpxxy that is 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm lidid3v 1n pwa7:(zkbn+ne in the spectrum of a star which is 100 m3a (17bvki zwn d+:ndpillion light-years from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 10e 3(2 aw d t)wh/4sua:zjy:bwe13 K. What energy (in eV) does this corresp euwhd)wtjb yzsw4 /e:a :a32(ond to?