The appearance of the great range of brightness av8 et awn/j5:bmong stars is due to

  The absolute luminosity for most stars depends on,m) 4hdglf wfy3t+p 7h the

  Four different main-sequence stars alwf6kr4z0a)fwkz bvkby(638 re colored blue, orange, red, and yellow. Whatvza k8bf yk6b6r )w3klf4 z(w0 is their rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stardj hai xsa/o5i4c30qz o+y-(v s on a plot of

  A white dwarf star with a mass equal to that of the Sun is about 3r3j+ -au/hf:omk ld lthe size of

  The Chandrasekhar limit of stellar mass (below which a star will collapse in/2 qs3 d ,kskdhut;; 4vso8.siymd *coto a white dwarf) is, ;,; dk qoh kds c/myis8.d4u2vsso*3tif the mass of our Sun is M, about

  Supernovas are thought to alway* piluj xnr ao,(v7mm4b0qw3/s result in

  Black holes

  Pulsars are rapidly ste gantoi(srj06-w/agx/* v7 pinning

State Einstein's principle of equm: b6u 7mv1cmoivalence.

  The Schwarzschild radius of a black hole is tnun/f x t1nqm ya38b7,hat radial distance from the center 8qmf3 /7yxa ubt n1nn,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 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 particulary)bw- dw ;h3b;c2 a*jxj(r +jpibjb2v wavelength in the visible, and the source is mov-;bjjbpbijaw h(+)3 db2v *r j2c;xywing away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation correspo fn.l:qg 9k 0c:s rsri+ltfl)7nds to a temperature of about

  The Sun has apparent brigh6hfyo1;;l) t0qm-i6 illbp0s sle5vy tness 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 yvpl o li, g9x36+-dq,z7p v 70msokbothe 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 mec/bp xu;fem8a(rr 19f 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 km?

  The Earth's orbit has a me5 )ez6 bgq)higm;58 co(.*axu9fdijr) gbtaean 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 Centauri, whi:dy4a e2 ;tq0-c5mu-cz ryko ech is Earth's nearest star at 4.35 mk-ezo;yect4ayr: uc02-dq ly?

  The apparent brightness of a;rn0vmv txlwn9s.h 8-z w;9 yl 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 agq0u2ucnkq 6- pproximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Ml 6-g2c0kqnu uqy, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0%m,z7c+ ss00qtze r9 rsz:e8fa of the speed of light, how far away is it from u +:0z780zeqt, 9 smes acsfzrrs?

  Estimate the speed of a galaxy that is 10 billion ligh:os*8he vkkv4t-years away.

  Estimate the observed wavelength for the 656 nm line in the spectds4ks ud0f4 j2rum of a star which is 100 million light-years f2ds d0jkf 4su4rom us.

  About 1 ms after the Big Bang, the temperature off z9b ot6+gna .ad;7ima6f :vx the universe was about 1013 K. What energy (in eV) does this correspond bx9 i+6gn6a7o:fdtm. fz;avato?