The appearance of the great rangik;xe7 9uah i5+ dzpv.e of brightness among stars is due to

  The absolute luminospp: vx, t:ds/nity for most stars depends on the

  Four different main-sequence stars are colored bl +y7m;w4rijxk ue, orange, red, and yellow. What is them wijxy4 +7;rkir rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on a pc1 9n(ptgd:p ilot of

  A white dwarf star with a mass equal to that of the Sun is abs0:9g e mz6xcfy9eqn4 out the size of

  The Chandrasekhar limit of stellar mas vhsk19/s( ypls (below which a star will collapse into a white dwarf) vss(h/ykl9 p1 is, if the mass of our Sun is M, about

  Supernovas are thougt 5+;vr dph0zj4 mukz;ht to always result in

  Black holes

  Pulsars are rapidly or6 p3 esr;kv/tivj09csa 0uth7c e28 spinning

State Einstein's principle of equivalence.q4uuv1wlwc*e q,pi b0)(ecc *

  The Schwarzschild radius of a black hole is that radial distance from the xa aqw34u5 .zgcenter of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general reg.ax a zu4qw35lativity 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 8 tyt .e 3qd 0p./rbygpj)kk kco/:aqfd7* x3uthe visible, and the source is moving away from us, the color of the lb8kfk)g/oy0rtj. ek ty./c 7aqp *qx3:dp3 duight appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperature 6rp;dfff4dcc5 -h g.lof about

  The Sun has apparent brightness8sw9yiox8ijv xnv:6 ) hp k2.j 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 luminoh8 hdzcnx d20+sity 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 mean radi .bb j/j dmb7svf+k *f++e z8sp29tlnbus 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 mean radius of s/. cl+1agl(w4w in-sph-vvy$1.5 \times 10^{8} \; km$. 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 sxe pgkm;* p;23zq6qg ytar at 4qp3zq; egm62*gy ;p kx.3 ly?

  The apparent brightness of k *f5kf1m7gnw 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 agq ,w+lnm05zcz3w n etj07ptir0:r* nle of the universe is 1/H, where H is the Hubble constant. Taking H = 20w z0r* i0wtcen 0 3zl j5t+r7nmq:l,np km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is movinv2swgkn1j/4 )y7u.:qa hu1b lj 3 dskdg away from us at 1.0% of the speed of light, how far away is it ukuqdl k/3ys.):h1s12vwj7n j4 dbg afrom us?

  Estimate the speed of a galaxy that is 10 billion light-years awzpua*4kmzz + h;8 xjo8ay.

  Estimate the observed wavelength for the 656 nm line in thkq:.ea3z o-c), lxzlln,,ipee spectrum of a star whichpcze.xl n zl,:l, aq,3)-ok ie is 100 million light-years from us.

  About 1 ms after the Big Bang, the temperature of the universy)ro8 gvi6m i b1tk(8pxct)g 0e was about 1013 K. What energy (in eV) does this corr bx8gcmkti ) 0t(og 6rv1iy8p)espond to?