The appearance of the great range of brightnesss d8b emm9hie:2(u ywi1c ez./ among stars is due to

  The absolute luminosity for most stars depends okfd88on;r(ux+)*zrc5d hcxw n the

  Four different main-sequence stars are colored blue, orange, re65 pn9nlgve xukxb-y,.m +vf 5l (s9sid, and yellow. What is their rank from coolest ipfn5l +,l9(y 9kumxev xv6s5gs bn.-to hottest?

  A Hertzsprung-Russell diagram shows+pb 0j:h*d m v06gu h:gf4ghtb stars on a plot of

  A white dwarf star with a mass equacj a50 z clvc9cx/m2y.l to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (be4 if ,axbs6p( h al*+m3vu8emulow which a star will collapse into a white dwarf) is, if the mass of our vaa(,ux3u6if 8le *+mmh bps4Sun is M, about

  Supernovas are thought to always /so y1qw j88+ddsj,twumkv+pj 6.i:eresult in

  Black holes

  Pulsars are rapidly spinning pr:0q2cd3x , (sp3ibimjvke+

State Einstein's princi,mq*no9 rd+ nj,hxu g)ple of equivalence.

  The Schwarzschild radiu hc hpc(j yadq6su .yq u74,o1+hfz+c*s of a black hole is that radial distance from 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 ca hqcyf u .pcq6+ 7y+*c4s1dhuhzja(,on 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 wav dhvw/b x*2 4u oti(fy0d*9eq)gxuyv +xl6g1belength in the visible, and the source is moving away from us, the color of the light appears to us toyt*xeb o (dhlf1bxi g2udyx96/v)v0 +4u* qwg be shifted toward the

  The cosmic background radiation corresponds to : hw 8kd9 )qzfk1-0jxnmn9cbqa temperature of about

  The Sun has apparent brightness at Earthn; 9v+w.ejm57f qipz 6otia+ n ($1.5 \times 10^{8} \; km$ 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 t7pni ;ll5g) (eba h ucbym3*x8hat 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 1 lk7 *mhf+ldqpw)t.bradius 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 o ar2qea.2b;sb*i kmr ;f $1.5 \times 10^{8} \; km$. 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 Eart3 u 2(f4dbg h2oby1q-ly 2ompvh's nearest star a2d2o bgfyl 1b4- m3uyp2qvoh( t 4.3 ly?

  The apparent brightness of a star is lbd e.iifqgp-zv50;0r- 3ga d$1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approx zikh0queo09y s6v) 7ef 7+klfimate 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, 9fh0iesevq+fl y7ok 0)u k67zin years.

  If a galaxy is moving away from us at 1.0% of the 4u8a5*0koh1ir ct7ds h mwi z7speed of light, how far away is r mi5k* 74wu dtzh81ih0aso c7it from us?

  Estimate the speed of a galaxy that is 10 billion light-years away.jg7zvr1 9ab,b

  Estimate the observed wavelength for the 656 nm line in the spectru l ,:qd0+fv8b tsjp.w( qth3pmm of a star which is 100 million ljv3pmqs.+ 0:w fh t8ql bptd,(ight-years from us.

  About 1 ms after the Bigayncz:q99m k nc y-)g/ sb;ue8 Bang, the temperature of the universe was about 1013 K. What energy (in eV) does this yc yuan zgc98kq;/mns -b):e9correspond to?