The appearance of the b4bq ) j1to 8xdj ygdt*swp-17great range of brightness among stars is due to

  The absolute luminosity for most stars depends on b.t3gl /z/ct ethe

  Four different main-sequence stars are colojjq gj:x;vf;l /6ye 0pred blue, orange, red, and yellow. What is their rank from coole6 pylfjjg;x je/;q0v: st to hottest?

  A Hertzsprung-Russell diagram shows )z-6on8s bqec stars on a plot of

  A white dwarf star with a mass equal to tha ax1/fs9a2vyx t of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below which a star will collaqgh/gc3k) jn,uxjz 0+pse into a wh0 j)xgkjhnc/qz,g +u 3ite dwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to alxs ny7 dxll h1j.41,uiways result in

  Black holes

  Pulsars are rapidly sw/ysm:0o0q wu pinning

State Einstein's principle of equivaldjj6oa zf)v;l dm*0 a;ence.

  The Schwarzschild radius of a black holuo :rw,v(fxtf0sf93 e)d 0+k (h qkklge is that radial distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his gene(dv,h xrf3s+ t(:q)0ogwfk 90fkkul eral 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 particular wavg7; vuwgh25lm( nd f+r7,aha4mti;en elength in the visible, and the source is moving away from us, the colduw lagh;fig7vt2 r+(n ;n,hm4ma7 5e or of the light appears to us to be shifted toward the

  The cosmic backgroundkpbiz7d ;cq7.izg6 84isyx d0;m l:nn radiation corresponds to a temperature of about

  The Sun has apparent brig 0dt3j6-;i ts:j h0qwi*qz xlzhtness 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 luminositvn/ x g6cn*ofu2,wipt9e5 xbzdp0;g4 y 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 kvxdyw5 jr*+6mean 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 radius keku8 qb :sx- ogct1mk,,.rs8 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 jn au3gi.: sewv3-d24 h9qecvangle for Proxima Centauri, which is Earth's nearest star at 4.3vc gsnd23-uaee34 v9:ji.w qh ly?

  The apparent brightness2pb ; xxaa/98vk dr2ejmac: 3 rh3b,qt 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 approxima2,hdutw +.lenj qk y1yg+ v*w1te age of the universe is 1/H, where H is the Hubble consta nw.1hu+* +qtk,jylgy v2w1e dnt. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from r5ela37 l)o mr: le plf-a(xg/us at 1.0% of the speed of light, how far away is it fr:(o l)a-xepflg3llrm ae7 r/5om us?

  Estimate the speed of a galaxy pm3 isuxh01s8u( h,swthat is 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm line in the speclvuy u n5 8soyxd;8oy8s65*putrum of a star which is 100 million light-years from u yn8u ;58ss568 oxvyld*uoupys.

  About 1 ms after the Big Bang, the temperature of the universe was amjj+lzjsx j;k69,xq8(c8ntobout 1013 K. What energy (in eVj, jjxjzkc n+xs9t q(om8l68; ) does this correspond to?