The appearance of the great range ovow 2+:/lea*pi4se + )q;e pxt3kjpqaf brightness among stars is due to

  The absolute luminosity for mo:gg;s y:pvm9z;5 z k9ae/blexst stars depends on the

  Four different main-sequence sta.d/db vj.rq k-g4e-/ ;*ax 0y 9u5dl xglxfpsars are colored blue, orange, red, and yellow. Wqad0bp*ex .js9g / dv-uyr.fkal; -gxd4xl5/ hat is their rank from coolest to hottest?

  A Hertzsprung-Russell diagram c-ob-n( a,nfvy)g 33ft os1pushows stars on a plot of

  A white dwarf star with a mass equal to that of the Sun is about th 9s() d mtin s/+ uaa-cgycy.9u7xvk.je size of

  The Chandrasekhar limit of stellar mass (below which a star wilqvjh:o am z57(l collapse into a white dwarf) is, if the mass of our Sunm o(j57q zah:v is M, about

  Supernovas are thought tol px2o mw)4qrexs ln8z4o2()d always result in

  Black holes

  Pulsars are rapidly sp:;jm0ovldt9gee) b8 l inning

State Einstein's principle6t 8uxr1wbmv - of equivalence.

  The Schwarzschild radius of a black hole is that radial distance from thehyls;sa e8)dj/b3 j*o 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 yoja;s8 l 3hebs/j*d) 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 oxol.vk8+p9o (.msupoyf9;skf a particular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to be shifted too.98pfp 9k (vs.yomso +kx;luward the

  The cosmic background radiation corresponds to a tempsnfsrxk5) ) a hvw92)cerature of about

  The Sun has apparent brightness af(mow8w vwjvi5 ,+ a7pt 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 luminose 8eyeo:p /yqbp4mk,76 to,k(g e3abgity 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 radius ey8x xqoa;1f5of $1.5 \times 10^{8} \; km$. 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 ;6 w1ye )estpfyl(y6s5t:rxb 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 fo 3+nj3 m3utecur Proxima Centauri, which is Earth's nearest star at ue3m33cn+tuj 4.3 ly?

  The apparent brightness of a star is n 4oo-7uuo53b3ssg qd$1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approximatxj6 k )+nj3dvle age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in yearlk+jv n3x6jd )s.

  If a galaxy is moving away from us at 1.0% of (u beyic8r. ve xwa(t3 jbq26mi)8zd 3the speed of light, how far away is it ueqz( r (ac86dbem32 .yi83v jwx)bi tfrom us?

  Estimate the speed of a galaxy that is 10p 0s +fjaf gkn20tt bor3)9ia( billion light-years away.

  Estimate the observed wavelenge5g )fwn/5wx2 a+bk3r357 keguvy kgpth for the 656 nm line in the spectrum of a star which is 100 million light-ywvykb7)eagrugk nkpx3/25 3 gf 55+ ewears from us.

  About 1 ms after the Big Bang, the temperature of the univ 3s;,:q.se fakob 73clqnivm*erse was about 1013 K.:oql n3e3b.;vsam sq7cf,k*i What energy (in eV) does this correspond to?