The appearance of the great range of brightness amvsy +vkso:9i. w; 6jfaong stars is due to

  The absolute luminosity k+)gq jr23e+yqbwbl yp/34yyfor most stars depends on the

  Four different main-sequence stars are colored 5qiqzgmi/*+h blue, orange, red, and yellow. What is their rank from coolest to hotti +5i/zhmqgq*est?

  A Hertzsprung-Russell diagram shows stars on a ; cak0ip5b4k 83 6frk8r jckjmplot of

  A white dwarf star with a mass equal to that of th:;t7uhv -6qs cy/lwv26ymhid e Sun is about the size of

  The Chandrasekhar limit ;6pxav 1xbfk5 of stellar mass (below which a star will collapse into a white dwarf) is, if the mass xfvpx5 16abk; of our Sun is M, about

  Supernovas are thought to alv0hy, ige1wz 7e6+wc povoy9 7ways result in

  Black holes

  Pulsars are rapidly spinno(a slitn*vf bcm-7 7;px vou l54h4e-ing

State Einstein's principlev3:)m*q ims-p0o s 43us2 llq+vavr yx of equivalence.

  The Schwarzschild radius of a black hole is that radial dist,fcn x) -z7bz oxr51jzwg0v t;ance from the center of a sphere within whxz)o,t1n 0 z7vrzfwbj5;x cg- ich 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 pb/ b0p(jk 2 wk,nn1ndoarticular wavelength in the visible, and the source is moving away from us, th/b0jowk2n n, p1 kbd(ne color of the light appears to us to be shifted toward the

  The cosmic background radiation correspond 03 glsus4(z5zi8lkiv5 xni pvqa)5g0 s to a temperature of about

  The Sun has apparent brightness at Earth (xhgp,3m ld5l 463ugxk $1.5 \times 10^{8} \; km$ 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 e,t/k l,p ospxt99;mbwp1/bey qual 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 6f5hx.talg) t a mean 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 radiw ,8+u1xptvp +8r mywyus 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 nearest star7jv fe2 1r0mqk at 4.rkq0f7m v21e j3 ly?

  The apparent brightness of a6 jwf /c mp(is115tnjn 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 t5 h3 gfn5rd9elhe approximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the e n5dflg 395rhuniverse, in years.

  If a galaxy is moving away from us at 1.0% of the speed of light, hnwen. v(hzv8,j b q,o6mqk/ jr 96spd+ow far away is it 6k +esmdnwb (h9qoqj rj,np68/,zv v.from us?

  Estimate the speed of a galaxy that is 1sgu/p zm,qb8kl4r-/ w0 billion light-years away.

  Estimate the observed wavelength foof s 7ezw1p9g(r the 656 nm line in the spectrum of a star which is 100 million ligh9 (fzp7gs weo1t-years from us.

  About 1 ms after the Big Banj;ht8- cjk ey,g, the temperature of the universe was about 1013 K. What energy (in eV) does thht8;c,j jye -kis correspond to?