The appearance of the great range of brightness among stars is due to r8v:ta9x,adp

  The absolute luminosity for most stars depends onbwp)7g)lq79o jma ov7mh(i9 d the

  Four different main-sequence stars are colored blue, orange, red, and yellow. Wmqr0o kraqx, ,i o*3(xhat is to,(*0q airkr 3 o,xmqxheir rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows sywm 7qp7;o3bv tars on a plot of

  A white dwarf star with a ma 9jhhi a-oqs*5ss equal to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below whi k0jmmyfk* ,m fm;c8-z8iqa*gpjw6 :hch a star will collapse into a white dwarf) is, if the mass h*j c6mz ag0*;,mf- :8jkwf kiyqm8pm of our Sun is M, about

  Supernovas are thought to alwhj :k k*ycex w eik/48kro3i2:y7 yp9gays result in

  Black holes

  Pulsars are rapidly spinq x5p)r m1n ;2fj 64muegwdoz.36qna jning

State Einstein's principle of equivalence.q:peo+0f arf b.eo; )b

  The Schwarzschild radius of a blackk6ivlb1tx/t1uasi9b6 79h zc qnl4s+ 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 theorzsbiqi6t lux96741bv+1ksn9 l hc/tay. 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 emaoibu70v-b w5w-7 juv its light of a particular wavelength in the visible, and the source is moving away from us, the color of the luw7a5owb 07jibuv v- -ight appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperature of about46oc0 yt/+jwc ; gtfb )fstx*c

  The Sun has apparent brightness apx/ )qyfdd;gh k. 7q-2 jk1vget 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 lumi2-,+ix ap4l j4 0deezf ,0xigc 2krooznosity 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 4gfgue;5e+t3g k 7v2 mkv-qm vmean 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 - 1d9 y0gqgxeoa mean 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, which is E5.gra lt qz.s h,/yh2carth's nearest star at 4.3 lylta,g..y /rhhc zs2q 5?

  The apparent brightness of am6h.sj0t nb3kyh+ mnf 02v ;do 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 approximate age of the universe is2 zv m(9qhqdsu. ee77r 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly,mh.(dzsu7ere 7v2 qq 9 estimate the age of the universe, in years.

  If a galaxy is moving away fsb -qq)oq67p 3u1p,iqluwt8 d 7lgi8*ag p2xxrom us at 1.0% of the speed of light, how far away is it pi-i 7a1l8)7qlxqbpodg3 *t, qu 2xqp8 wgus6from us?

  Estimate the speed of a gala+7de +ip goaq7xy that is 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm line in,jof82vie+z 9hmk ,;t r p*mnp the spectrum of a star which is 100 million ligjk,mi9n *f; +z2rpoh,et vm8pht-years from us.

  About 1 ms after the Big Bang, the temperature of the univerq st;t goum* pu/;93bpse was about 1013 K. What engu;u ps3 b/p* m;9totqergy (in eV) does this correspond to?