The appearance of the great range of brightness among stars is2pl evbt6f9 .s due to

  The absolute luminosi aq8*5gzn3pnbty for most stars depends on the

  Four different main-sequence stars are colored blue, orange, red, and yellxly4 n(f8i l: 4q*ialvzka l e0)1-ftyow. What0*t- )8y4y kf vf1niailzl4xel: (qla is their rank from coolest to hottest?

  A Hertzsprung-Russell :7p;* zow07hi1zae l,vr-o inivi 5eqdiagram shows stars on a plot of

  A white dwarf star with a mass equal to that of ez*i4dksk+ a1eslh,v px;):z the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which eij rd-;x0( vxa star will collapse into a white dwarf)e-x vrd; i(j0x is, if the mass of our Sun is M, about

  Supernovas are thought to always rei s4 -neukrloi p*i)74q2p0ihsult in

  Black holes

  Pulsars are rapidly s1c-t k6utbp:t,*/agdyp l)xf3 )fbkn pinning

State Einstein's princnhk84h8ztnal.b 2 -cg iple of equivalence.

  The Schwarzschild radir6)p, xbr- gddus of a black hole is that radial distance from the center of a sphere within which nb6 rdd-r) xg,pot 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 5 2rq)+glyh1hqvtw. t a particular wavelength in the visible, and the source is moving away from us, the cqlht + v5rg 2ty1)q.hwolor of the light appears to us to be shifted toward the

  The cosmic background rh-9jl 7hckew1 adiation corresponds to a temperature of about

  The Sun has apparent br2ov2c keie b(7ightness 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 th3(w ,yuq m-latat 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 meod;hd p.w:(6xbh.r r can 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 muw yw)056te;9w lif s2pj:tcy ean 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 angl-c7rex. 90oiqyq. )k4sydk mtli/p; le for Proxima Centauri, which is Earth's nearest star at 4kid;x/7lm9ekosp 4q- iy0ry t.. q)lc.3 ly?

  The apparent brightness o nx3bmm7/ 01 p rhxj95qkqib6gf a 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 univeryad*ls2a/i g;se is 1/H, where H is the Hubble constant. Taking H = 20 k2y li*s aa/g;dm/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of t77s 8pto;qpa 6 nbfg;vhe speed of light, how far away is a 6;8n f7op bvpgqt7s;it from us?

  Estimate the speed of a galaxy that iyt/m v hdwksb 5 my,.rd;kb*.;s 10 billion light-years away.

  Estimate the observed wavelengthe y2 yqwkz638/s p41l hgr0ch/3wj bdirl1b (k for the 656 nm line in the spectrum of a star whichiw1(8bb/lhk6q elzy32psrydk1wgr/ hj04 c 3 is 100 million light-years from us.

  About 1 ms after the Big Bang, the te0u(zdw(h u h8gmperature of the universe was about 1013 K. What e8dghhu0( zwu(nergy (in eV) does this correspond to?