The appearance of the great range of brightness among sl a0v r(kc//kpqd hz8/tars is due to

  The absolute luminosity for most stars depends on th2c c b ncp1hsu bud)1n8k2a-4oe

  Four different main-sequence stars are color2n ;cr zzta+7 :rkqjr*ed blue, orange, red, and yellow. What is their rank from czc :zrat k j*;r27rqn+oolest to hottest?

  A Hertzsprung-Russell diayq*-vlat- c x/gram shows stars on a plot of

  A white dwarf star with a mass eq/ i-zgh) fuzy)mv1 *trual to that of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below9 :q4ie.nd( vjuqlgt0w 9v3ko which a star will collapse into a white j ig4:t90vwd3 kql(9.evunqodwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to0rbj,e9(nz(u yvzq3bz +y) p j always result in

  Black holes

  Pulsars are rapidly spinning4(ik,5thvch cn.2pck

State Einstein's principleuyc ;/ux-7tmn of equivalence.

  The Schwarzschild radius of a black hole is that radial distance from the centz);t0j3up- j g l3wczbpqydj-ah ;,t*er of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can beba 0pjy3z h j,p-*q3ct- ;w jtzd;g)ul 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 p8 evggjjal-8:kv67sw articular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to be shifted towardk j 86wvga-87 jvgles: the

  The cosmic background radiation correspo - q7(vchsm6(tncmo ; fq)4ejunds to a temperature of about

  The Sun has apparent bri2twjvwm x* vd0(bzu;9ny( m, hghtness 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 luminosioyk9gy69 e6vztjvk78ty 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 radiu,q kgeyy5o)s;s 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 mean4 x7 0s0aj2,m +7xxdm ltcnpt7pag0 fx 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 : gm**.l qyapiProxima Centauri, which is Earth's nearest star at l*.qy*:mp i ag4.3 ly?

  The apparent brightness of a star is t4t5hr,jdum4b.56un lh.xjl $1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us.

  It can be shown that the approxi:i ( ooq1 :p/b tnu2b(:ndij;jpvaj2fmate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the u1io:ni;bbapn:(fu2vptjj : ( d/q o2jniverse, in years.

  If a galaxy is moving away from us at 1.y5 sve2-l 2zse0% of the speed of light, how far away is it from us? eyvlz-s e252s

  Estimate the speed of a galaxy that is 10 billion light-years away.+uhnfgr3;u :l

  Estimate the observed wavelen2v(fxj : 2ng piipy;s.gth for the 656 nm line in the spectrum of a star w y x( 2ipj;:2sfpngi.vhich is 100 million light-years from us.

  About 1 ms after the Big Bang, the tem;r2;ww xxe /zaperature of the universe was about 1013 K. What energy (in eV) does t ;/ xx;wrezaw2his correspond to?