The appearance of the great range of brightness amongw8.*yg o fm q83vl.1g n :ibylfl8;7io1yxdyy stars is due to

  The absolute luminosity for most stars dol;yw uo zi/r0t7-mu 3epends on the

  Four different main-sequence stars are colored bluedc(/s:9gwj1srxe55r l ixdwbxd ):0q , orange, red, and yellow. What is their rank from coolest to hott:5:/xgxw re l dxicjw5ds s10br9dq) (est?

  A Hertzsprung-Russell diagram shoo+33pfu vbq l+ws stars on a plot of

  A white dwarf star with a mass ze+-7 (eubnd uequal to that of the Sun is about the size of

  The Chandrasekhar limit wgtg5 e2dt5w( g) s;umof stellar mass (below which a star will collapse into a whit2w )gsm t(e5 g;d5gtuwe dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to always result 8oad r*sukayz u5u0o 4h,.i-wwgk63s .a ew+o in

  Black holes

  Pulsars are rapidly spinnoewokro 1t +sep4) 7l,ing

State Einstein's principle :jb-kdmcqlyk 5 33o, hof equivalence.

  The Schwarzschild radius of a black hole is that radial distance from thecfk2k3m;( qemy* 6r*bi4la itujhs /6 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 relativitksjy h6b ka3et;(mrmcq fi*2/u *46 liy 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 parti)y./iym(cj n yeft 9a0cular wavelength in the visible, and the source is moving away from 90i.mtfyy /cn()aj yeus, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds tn czc+:b +s1 h/mu8 (ahu3tid xd.6nmto a temperature of about

  The Sun has apparent brieol :. *lw2whjghtness 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 eqic0cy(u 7ql1x ual 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 radiusw)j4+ bwbvr m,nukm, j:l 9w*y 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 m4h/ *zpt7anydean 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 angleth;*t(fa tti2 for Proxima Centauri, which is Earth's nearest star at 4. *(i;tthtf t2a3 ly?

  The apparent brightness of a kdw 9ak4 ,(vhlstar 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 is 1/ vznyd*7.b*7 zio l-wyH, where H is the Hubble coo *v* -y.iny77ldbzw znstant. 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% ofpd 8t5cbcn3 f (,g,zwh the speed of light, how far away is it d 3w,gh(z8bp tcnfc5 ,from us?

  Estimate the speed of a galaxy thabwz/ whyo6d6ww0 -fj3t is 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm line in thed/5,pt u.bj2ozcc wh+ spectrum of a star which is 100 mill2c./w t+bch5z pujd o,ion light-years from us.

  About 1 ms after the Big Bang, the g4 lcklx3-:.zt7*ety6wwk fntemperature of the universe was about 1013 K. Whz3 f4nekcx7ky*tw t :6wl-gl .at energy (in eV) does this correspond to?