The appearance of the great range of brightnesa9(qzwy m7rfd88 m+x ks among stars is due to

  The absolute luminosiadspi(06 8pm8k xp 0xkty for most stars depends on the

  Four different main-sequence stars are colored blue, orange, red, hkp5stc 6t26q 7vkeakz;o ( 6jand yellow. What is their rank5(vohsak z67q2tek;c 6jt6pk from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on v)jwoq, uqz8+a plot of

  A white dwarf star with a fvl l txlwhh7 +no558 x(lqi0+npsc91 mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below wyd)i*;xs tqp .hich a star will collapse into a*;x.sq) i typd white dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to always rescd6po47 9c.kk4* deecp (hsbmult in

  Black holes

  Pulsars are rapidly vigeoik2s y 8 .ixjv4cmigp a..)4z :.spinning

State Einstein's principle of equivalen 4 kq*uo2t3gd 3oif0hz* cnzs5ce.

  The Schwarzschild radius of a blq ci (4cjht6-pack hole is that radial distance from the center of a sphere within which not etih4 p6j(-c cqven 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 particular wavelength in the vis4vk,hug z2s1q :+st ldible, and the source is moving away from us, the color of the light appears to usvtdsh 4gqzl: u, sk2+1 to be shifted toward the

  The cosmic background radiation corresbt ycxf0yzn+ q4 p7+h7 ux/+2fe +grbfponds to a temperature of about

  The Sun has apparent ;. w tgfypmq99lc943zdqey5mbrightness 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 thpv+6x8 f+ phkae 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 of ze *1,un0chz 2b d5uk j(ozq) rg:aye8$1.5 \times 10^{8} \; km$. 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 radiusc 87;n izdv4d8deue*u 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, which is Earth's nearest sgnwtt *5l)tq4n 3o( h;epq*au tar at 4a o*l()tg5n h;n ep4q tqut3*w.3 ly?

  The apparent brightness of a star is tetos4zi 2)z201 n*iwu/ywybw8l )mi$1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approximate *y* kzeb; b0tqyr(u(kage of the universe is 1/H, where H is the Hubble constant. Takingbkz tky(uq*re ;b(*0y H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of the speed of light, how 11 jvpylvm+)1i ,bhqpfar away is it from mhb,11l+iyv p j)pqv1us?

  Estimate the speed of a galovnfok mp6ez*k9+lkg2q2 w7*o6raf 9 axy that is 10 billion light-years away.

  Estimate the observed w13jqrjgyh ai(:6kr7 -tqrymb )q1 ( xcavelength for the 656 nm line in the spectrum of a star which is 100 million lq 7:hxmqyrt 6)( 3ygbqrj1 -a 1icrkj(ight-years from us.

  About 1 ms after the Big Bang, th.an 3yi1fgkcx33 g6 z8 t n0aoq9oi/szayf6/fe temperature of the universe was about 1013 K. Wha 3fn9otn ogiizf0a33c./y 6 y18sgxfaakz6/ qt energy (in eV) does this correspond to?