The appearance of the great range of brightness o32zzuke+/sci.h , xjamong stars is due to

  The absolute luminosity for most stawx/;b yq;vc.xah- e0ers depends on the

  Four different main-sequence stars are colored blue, orange, retzxn)uui0),z1 a( 6 pgck0suvd, and yellow. What is their rank tu 160ukpzn i 0sz,a(u)cxvg)from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on avdlqzhrc ae0 ,d4./+:ob xx +p plot of

  A white dwarf star with a mass equal to that of the Sun is about 8 c:r0fk h 5uxd0- *v(;3n+ tiwbxbt ng,ihqznthe size of

  The Chandrasekhar limit of stellar mass (below whj3m *evxp9 z;hich a star will collapse into a white dwarf) is, if th pzj3e*;9v xhme mass of our Sun is M, about

  Supernovas are thought tom9e5tupx0t ub;)ceszi-0 f+f always result in

  Black holes

  Pulsars are rapidly snr9mri 7r89qmpinning

State Einstein's pri (c 3+ap2rx6sso+d -plqg1yc gnciple of equivalence.

  The Schwarzschild radius of a black hole is that ufi)etn6urj:j4 ac1q2pq .:q radial distance from the center of a sphere within which not even lighqta6n .2fuip4j: j1ecqq )r:ut 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 emitsum4bomngt c 6r/dp-ml : eq/gsdxva o2-*(w75 light of a particular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to be shifted6pmm*/2 o-:4vg 7 q- obg5(/rn ewadc txsdlmu toward the

  The cosmic background radiation corresponds to a temperature of rc t6 k1cx.vo d1r4j :en.,njzabout

  The Sun has apparent brl9l 5ke; vdq5gightness 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 nyg eqe/:+tk:4wm sl;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 radibei 0kh/q8vv.4t h x;zus 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 m5f gr/ mpy.rh47cjq9nean 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 angle for Proxima Centauri, which is Earth's nearesz 4z 9z a pgrwf45)*/5ebjnejxt star at 4.3 ly?r4fx*e n9 5j)/ gjza zp45wzbe

  The apparent brightne ka d9ku03;hitss 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, wherncguq:x0hekv) 4nu bjz4 u:;6e H is the Hubble coexuun)z0 q;6c nh k4j:4bvg:unstant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away : (px yk-q1 tte 5*9wg+8:thwaqtxhmu from us at 1.0% of the speed of light, how far away ishp-q*ut kt eawyqx:h:8 w1t5mxg+ 9t( it from us?

  Estimate the speed of a galaxy that is 10 8r 8q6riplze9 billion light-years away.

  Estimate the observed wavelength for the 656 )hth+) ckp cc:e*zq5unm line in the spectrum of a star which is 100 million light-p+5*hcq)che:t c k)uz years from us.

  About 1 ms after the Big Bang, the temperature of the universe was about 1013 y(tdlhx3cl+o 3 )zw9t K. What energwt )93l y3c( hx+otzdly (in eV) does this correspond to?