The appearance of the great range of brightness amoa5s*;mmt5fi 8; e nqhqng stars is due to

  The absolute luminosity for most stars de foown9+h..* gox,qlc pends on the

  Four different main-sequence stars are colored blue, orange, red, and yellow. lmftjpr2,2 ,kycsjew 3 o(*i3d0 ind-What is their rank frof,r, lis yc j2-d32jinke(tmp wo 30d*m coolest to hottest?

  A Hertzsprung-Russell diagram sh agg: .:wqae+j:w1iia ows stars on a plot of

  A white dwarf star with a mass equal to that of the Sun is abpp4p t7w t eo6 og+cxn+h25e8vout the size of

  The Chandrasekhar limit of stellar mass (be a.6lreaw..nb9 fv nb1low which a star will collapse into a white dwarf) is, if the mass of our Sun is M, abouanwb1n fal.9 .6r.veb t

  Supernovas are thought to always re u7*xzb9 ,da k66: lx2fnhqektsult in

  Black holes

  Pulsars are rapidly spinvp66-p j ofjsn fh93xcksa9*( ning

State Einstein's principle t3w1uft*e 8jkof equivalence.

  The Schwarzschild radius of a bezv,to ter()mm1 /+ a.lgf5ltlack hole is that radial distance from the center of a sphere within which not even light can escape. It lv/g 5a(,tfelzm1.m+ort) tewas 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 a particular w45su k1mb .dv;mmd;ltavelength in the visible, and the source is moving away from us, the color of the light at5k l bs4dm. ;uv;m1mdppears to us to be shifted toward the

  The cosmic background radiation correspon+* xww o;g8lhsl. 7tcwuee6j-ds to a temperature of about

  The Sun has apparent brightness at Eargy dqt,qv7 yn-w4 p.*kth ($1.5 \times 10^{8} \; km$ 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 luminos ljxi7m:g:a9gx2((oy.bb l p hity 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 m.ie)cj9w;eqlid i7r 6ean 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 mean radius 8ihj wvm(oy)p ; .6n hfeyl8n0of $1.5 \times 10^{8} \; km$. 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 nip;q6 n;ldac+w/sc :Proxima Centauri, which is Earth's nearest star at 4.3 6l;dcn siw+:pca ;n/qly?

  The apparent brightn0o6e* m j;utwness of 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 universe is 1/H, where H is th5: cv 3q*bccqpe Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universec qv:35ccp*bq, in years.

  If a galaxy is moving f,nq fe23+;kse z2qpb away from us at 1.0% of the speed of light, how far away is;f qqs ez22+3 n,fpkbe it from us?

  Estimate the speed of a galaxy that is 10 billion ey: 7bgno*jw34ep mteimxy8s3:an) 6 light-years away.

  Estimate the observed wavelength for the 656 nm line in the sp ;2hz;ad1 dq wkq0q+pvectrum of a star which is 100 million light-year 2 d;wqvdahq+pqz0;1 ks from us.

  About 1 ms after the Big Bang, the temperaturezhz5+d: q)gq x of the universe was about 1013 K. What energy (in eV) does this chz g: 5)qz+xdqorrespond to?