The appearance of thx3v z6t gfoxh.mfkv d5u+)y36e great range of brightness among stars is due to

  The absolute luminosity for most stars deph5pmbl .v,zdq5s/z s5 ends on the

  Four different main-sequence stars are colored blue, orangozut+y.a9anoh , 82yi e, red, and yellow. What is their rank from coolest to hottestz29.iuya ,o8 t+oy ahn?

  A Hertzsprung-Russell diagma(jsljh n9+yl) r4l ;ram shows stars on a plot of

  A white dwarf star with a mass equal to that of the Sun is about the si/l(7/ vgya cwak6*7dm tf-qkg ze of

  The Chandrasekhar limit of stellar mass (below which a star will collapse in -i wfjz4kd(o;to a white dwarf) is, if i fjwd;-k(z4othe mass of our Sun is M, about

  Supernovas are thought dgrd+-5 i5lvy 3b9 x 2arntutl4u,sm9 to always result in

  Black holes

  Pulsars are rapidly spa6jwkk h097j 19ck n4 c3huxccinning

State Einstein's principle of/gy +mu76gk;m * z68rv prrc2)aynfkc equivalence.

  The Schwarzschild radius of a black hole is that radial5 y)1z1n2+se fdjrr oz distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwafsrnd)zoz+ 11 e r25jyrzschild 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 li:.ozagat( j.x ght of a particular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to b.x (aogatjz .:e shifted toward the

  The cosmic background radiation corresponds to s ;d5toxjh091sjpj/ma ,. yag a temperature of about

  The Sun has apparent brightne*du8jbv78g qfp/ a2dcss 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 o nti dilu6(u 9)j,c/kequal 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 mki- )vc ew/d6pean 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 radiuap7b7)guc c+:ys 7mlas 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 nem.+n+mmdca+xb7f + 1 rbipd- warest star at ++1f -ammm +ndrcb7x.d pi b+w4.3 ly?

  The apparent brightness of p-bak ygs t3(3a 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, where ndv,jp8v hde+ tz5p8-ir(nl. H is the Hubble constant. Taking H = 20 km/s/Mly, estiman.5z(8 n8plpdr,vvtjei+ h -dte the age of the universe, in years.

  If a galaxy is moving away m87fc6ab3s2 0 jtao5ekt0ty+k ceq c+from us at 1.0% of the speed of light, how far away is it +6ct8a k+ ke2emc05j s0yfcot7 abt3 qfrom us?

  Estimate the speed of a galaxy that is 10 billion light-yeam)0r gd96 gjyars away.

  Estimate the observed wavelen k22hnwmle)d,gth for the 656 nm line in the spectrum of a star which is 100 million light-ye mhewkd2 l)n2,ars from us.

  About 1 ms after the Big Bang, the temperature of 0,4s n i wsy:0tibh:gdthe universe was about 1013 K. ndyigi :b 4st:hsw ,00 What energy (in eV) does this correspond to?