The appearance of the.*k)cd t6taao:t n2qj great range of brightness among stars is due to

  The absolute luminosity for m2ulm:ngekz* ve0p 4*jost stars depends on the

  Four different main-sequence stars are colored blue, orange, red, an75xl/r qrim :1z e o)c1b95cv fovevf3d yellow. What is their rank from coolest e)fqr:1 r53/zfm xvb79vec lvco1io 5to hottest?

  A Hertzsprung-Russell diagram shows xna:-(1ewkgerzo )c2stars on a plot of

  A white dwarf star with a mass equal to t8k+oq,kz biid z ks- r,01nj1uhat of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which a sta ((tcgs:u- s1 ch ho4.cqt7ckzr will collapse into a white dwarf) is, if the mass of our Sun is M, aboutck1 c-(4:7tcsuhz oqs.cgt( h

  Supernovas are thought to always result i/(yucy, lz.*7os. *obdzd/t:vtsp sxn

  Black holes

  Pulsars are rapidly spi5uzoj 53vx.q /l4kdf enning

State Einstein's principle of equivalenw5 33k yf*uxzwce.

  The Schwarzschild radius of a black hole is that radial distance from the centergqe uf8 a93yh*ar:v :z of a sphere within which not even light can escape. It was first discovered mathemati9 * uhefg:aq 8z:rayv3cally 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 lightg8/ztak d -*m0wrwft0 ,fnx 7q of a particular wavelength in the visible, and tz,tfk*awn 0 7wtd 0grq8/-x mfhe source is moving away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation t2 tbj+ (,,vd*wade4d/qfbaq corresponds to a temperature of about

  The Sun has apparent brightsf,f.- cwwd m 7tup7w+ness 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 that ks.ztw+sq38 w 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 rad.zdvrj-2 ;gcj ius 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 h(g.d6,2u cpme(illr 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 anglej/xyx.h8: mvc/5lroh for Proxima Centauri, which is Earth's nearest star at 4x8:/ y5lxvc/hh jmor..3 ly?

  The apparent brightness of a s dz-.vk)sa)u0.ph ur3hoy :gx; 6f9kcwpfy/xtar 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 isd axe s6vvy:2 7f44cywsgg:5u the Hubble constant. Taking H = 20 km/s/Mly, estimate the agfg2aey:vs v:cg d 6y47 xsw54ue of the universe, in years.

  If a galaxy is moving away from us at 1.h hpk1x * hb3w4+ltn*j0% of the speed of light, how far away is iln4p 1h*bw kh3*j +txht from us?

  Estimate the speed of a galaxy that is 10 billion light-yed.zaen kr;7.u ars away.

  Estimate the observed wavelength for the 65en6o+h/ j2o am. bqqyp,nq +d-6 nm line in the spectrum of a star which is 100 million light-years fo/q-+qaoyne d +2b,6nmpj .q hrom us.

  About 1 ms after the Big Bang, the temperature of the un lss4g4* ll4zciverse was about 1013 K. What energy (in eV) does this correspo*4slclg4z4sl nd to?