The appearance of the great range of brighto cjr7a;*o tqs h8ll7zhhg j-,vd-6e8d mhz;9ness among stars is due to

  The absolute luminosity for m5m +vq7d7,d su:t7p xyzdoc g*ost stars depends on the

  Four different main-sequence stars are colored blue, orange, red, and yellow.obyfu *6 fg:f. What is their rank from coolesff:b 6*you g.ft to hottest?

  A Hertzsprung-Russell diax .u(6woerlk 31utw0 cgram shows stars on a plot of

  A white dwarf star wq p3)0zcvs x/7s;gzegith a mass equal to that of the Sun is about the size of

  The Chandrasekhar limit of stelx9jc 5smti b70lar mass (below which a star will collapse into a white dwarf) is, if the mass of c j07tibx m9s5our Sun is M, about

  Supernovas are thought to alway9 yw:5bforfdwl 5-bu 8s result in

  Black holes

  Pulsars are rapidly sp rj4s, f b .jsk,8h1a8swo5ietv /awi)inning

State Einstein's principle of y88vk)sr yx e(as4 w* d8pd3usequivalence.

  The Schwarzschild radius of a black hole is that radial distance from the center u8eh8bsyb2 ad6bhxv8 90kt0v of a sphere within wh2hsbb 6vvtbye08ahu d8 80 xk9ich not even light 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 emits light of a parjkis*) w 3o.9ixxgtl.mrcj 43 ticular wavelength in the visible, and the source is moving away from us, the kjgj .)mx9i w4i *x.trs33cl ocolor of the light appears to us to be shifted toward the

  The cosmic background radiatio5, ef- yyg1v ax5to5ryn corresponds to a temperature of about

  The Sun has apparent9v mg. 2*tsny*8vya kx brightness 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 thatm1:5oseb 5x .ze t-ltw 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 radius o 8unzn z xpamv2;-*qg)f $1.5 \times 10^{8} \; km$. 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 rxlk-sv*g os9 2 s*v)qladius 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 Centaa7lv diske74dq4q uzb/2yt 9 :uri, which is Earth's nearest star at 4.3 l74t2q ilz evs 9kqyu dd47/ba:y?

  The apparent brightness of a l (suzvh h25 mv)2 :::sizhgftw,b kv7star 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 thyk 0qjoj- uz.4e universe is 1/H, where H is the Hubble cjqz.4ko-0y ju onstant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us3w ,yr7yv ;dqz at 1.0% of the speed of light, how far away is it;q, 7rvy wydz3 from us?

  Estimate the speed of a galaxy that is d(icp1oj b l./10 billion light-years away.

  Estimate the observed wavelength foq)p.p) pu;xn*ys zfw .r the 656 nm line in the spectrum of a star which is 100 milliof* ;u )zwpspx .)qnpy.n light-years from us.

  About 1 ms after the Big Bang, the temperature of th6.zoonnoyk)u (-p;yd e universe was about 1013 K. Wh yzo6yd on-.onu(kp) ;at energy (in eV) does this correspond to?