The appearance of the gre*2 (1 spvqakdoat range of brightness among stars is due to

  The absolute luminosity for most6(zmzh i9kg) o stars depends on the

  Four different main-sequence stars arqt:;6,f7 qhfcu v7m:t/sz bzz e colored blue, orange, red, and yellow. What is their rankhfvsqt 7t7 m:z,z/ 6q:u;fbcz from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars on a v k+wc -a3 ul-nrpl0yl )h+fw.plot of

  A white dwarf star with a mass equal to oz. q*h: w.hrkbo40vl b18ubzthat of the Sun is about the size of

  The Chandrasekhar limit of stellar mass (below-tol xc b.9f /4)em hofj8ib1x which a star will collapse into a white dwm)t-xoh.xo f1elb4 fbcj 8i9/arf) is, if the mass of our Sun is M, about

  Supernovas are thought to always resuyod yu xq64v::801 bhk-wl9wpahenc,lt in

  Black holes

  Pulsars are rapidly sp0xr 3p ,yq(n zay:s4o- +fcdviinning

State Einstein's principly*iasgx2n2;z g1+8e5z f; z)czeyx lre of equivalence.

  The Schwarzschild radius of a black hole iw0 wb bgxh4;68iwprq4m vbcm( t20mq)s 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 publi 0pgb)tq(8w460w4mxhw;cirmb vb 2q m shed 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 particular wavelength in the visible, k/tsh.xmc:m y inc;h6+ us*b, and the source is moving away from us, thecb/;6kmy*:hsim cn+hu., s x t color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a temperatub4 o5ux: e*ocs dabr.-o artm3) p;x*zre of about

  The Sun has apparent brightness at Earth :)3eei u /qkl;f1e slce7o3dt($1.5 \times 10^{8} \; km$ 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 tjm/c)r;qcnc qo7w7 ;o *gs j3khat 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- juwkhhzwncw.*u2,1 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 mevc hi;(hq6os7e)an( dwq f2pgs) )g6can 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 Proxima Centauri, whing ns-(kqt9 h8ch is Earth's nearest star at 4.3(t8g nsq-hk9 n ly?

  The apparent brightness oom rrw20ia3)kf 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 approximate age of the universe is 1/H, whetak k s+/36vdk* :ns:xdwh xq4re H is the Hubble constant. Taking H = 20 +dk6 * x3anx::wssk4k hqvt/d km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away from us at 1.0% of the spet st 4smo;9zl:2a gbqirn21wsk(w ,.red of light, how far away is inbm9o1a s;r w(g4st :i,z2 2lskrtq.wt from us?

  Estimate the speed of a galaxy that iag /mr)oqr4h*;*a4hzyp tprxn2uiyn 88* 5yls 10 billion light-years away.

  Estimate the observed wavelength for the 656 nm lizipxgqh7 j q rh/:rglc-(ru753vf b 3:ne in the spectrum of a star which is 100 million light-years from :g( :fih ub5xj 7 vrr33pq7l/rzg -qhcus.

  About 1 ms after the Big Bang, the temperature of(wi-x q0ml 1uu the universe was about 1013 K. What energy (in eV) does0u1xw-miu (ql this correspond to?