The appearance of the great range c+wm 6u2+pxux0zl; fugd05 tb of brightness among stars is due to

  The absolute luminosity for most stars yqlm.v 8,wjd-15ttvxdepends on the

  Four different main-sequence stars are colored blue, orange, red0t:lb qk1jzu;(o7 jxw, and yellow. What is their rank from coolest to hottest0(jktj1 ulb; xwoq z:7?

  A Hertzsprung-Russell diagram shows stars on a pf(u 9;cy+ ahpbote /r1lot of

  A white dwarf star with a mass equal to that of the Sun is z4 e3fg;nz i.mwz,r vncz51f8about the size of

  The Chandrasekhar limit of stellar mass (below which a star will collapt.k zzr)6avv7 hu-m/f+,/e yx r5ngysse into a whr ,ehfk-/u5ayy zrtmz 6+s.v 7x n)v/gite dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to al o -rdod+mx/2qv- m,hrways result in

  Black holes

  Pulsars are rapidly spinning g ;,ern23vixi

State Einstein's princ q9s26aqsm6mq8( jrisiple of equivalence.

  The Schwarzschild radius of a black hole is that radian.)h) qj o:r(ig6cbec q)wom3* m 5aiel distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 19h 3 (rew:))qcg*a6o eo5q.imb)cjmni 16 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 wacz,nekyf3n b; *0kck0 velength in the visible, and the source is moving away from us, the n0kknkbf 3c*zc; ,ey0 color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperature of ab7lnb*7bvcf( ourc ;; wout

  The Sun has apparent brightness ay8 /a gtzsdn) t, k.rsq.bt mat6eus;.tsf**2t 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 the yl4dljn( (th4:drn5 eSun ($1.5 \times 10^{8} \; km$ 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 eupz7u+o ;jlb j.(/qoe3 k la8a 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 km?

  The Earth's orbit hasb*y5dc(nm2j z a 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 Earth's nearest s jvt3yhcg: ha6d7xbs 16 x8h0btar at 4.3 ly? 0a1b j:x73cthh6b8shvy6dgx

  The apparent brightness of a star isy08k(y2k az (czxb9le $1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the ap4o8n2 : etbbhyproximate age of the universe is 1/H, where H is the Hubo te:b4y 2bnh8ble constant. Taking 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, hwsf9 /c k:ig, /kqn,:spk:df9:jxsvnow far away isvji:/pc:kw:n /,n ks f,f9xdg9qs:ks it from us?

  Estimate the speed of a galaxy that is 10 billion ye1dw5g4/k(ecvku-c light-years away.

  Estimate the observed wavelengthgcwqlj7 +0k )sqg,gve;2 a.nc for the 656 nm line in the spectrum of a star which is 100kl2qc;0vcgs eg.a+wn g)j q,7 million light-years from us.

  About 1 ms after the Big Bang, t ya9pk/pw5uy2 he temperature of the universe was about 1013 K. What energy (in eV) does this k2u/y9wya p5p correspond to?