The appearance of the great range of brightness among stars is due tom ;e;l/weu9w5xq x.mgt+ o-r i

  The absolute luminosmy2 8e-ftxuf 9ehg 1f c.e7+saity for most stars depends on the

  Four different main-sequence stars are colored c-wkrwls p d-nsz.+:.blue, orange, red, and yellow. What is .ssw+cp.n:r kd--zl w their rank from coolest to hottest?

  A Hertzsprung-Russell diagram shows stars ona aw4 8uefk(rihcgoe8 g ,1u(( a plot of

  A white dwarf star with a mass equal to that of the Sun is4z *7sy )ke1f0skjwox about the size of

  The Chandrasekhar li r 1sdfj b:yi qwpnh*gt1(s145mit of stellar mass (below which a star will collapse into a white dwar 1*sf4sp1d1g: bjrihtnqy(5 wf) is, if the mass of our Sun is M, about

  Supernovas are thougpu/vl9;7b z da)kr x6o yc2pjr,3,qe cht to always result in

  Black holes

  Pulsars are rapidly spinni4 aws8qy+sha *gu* )ra(opf c.ng

State Einstein's princip(6/5p j t(kgidlq +bkoflv,4ule of equivalence.

  The Schwarzschild radius of a b 9 :o6hhed bcbst4(wd)lack hole is that radial distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild i )dc6bhd4sobh:t 9(we n 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 particular wavelength in the a gv-0uyxbukf (; p1b bnn:)7qvisible, and the source is moving away from us, the color of the light appears to us to be shifted toward tkn-quxba1n0 f;:g pb7 y ()bvuhe

  The cosmic background radiation corresponds to a temperaft5x 3xz/g-t uture of about

  The Sun has apparent brightness.5px71mb4olamex x .y 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 that of the Sudpnyn8wg; d-fb;p(on8 x,md6n ($1.5 \times 10^{8} \; km$ 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 of z7 ;;wk ;fl e .dd8l-gf9ua2apz.r vjk$1.5 \times 10^{8} \; km$. 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 radirc6kee o59mpp42n k8 ius 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 ).eug fp275td r7uvcynearest star at 4.3 lyy)rvuu2 7tg.7dce5pf?

  The apparent brightness of a star iana*+ xxe/)v/vdpv 36a ua7 pos $1.0 \times 10^{-12} \; W/m^{2}$ 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 H is the :4 ouaftj a(/b-heev. Hubble constant. ja. :ef(ob-4t/eauvhTaking H = 20 km/s/Mly, estimate the age of the universe, in years.

  If a galaxy is moving away zb qzjr,/ o1lpdf4c9 4hba k++from us at 1.0% of the speed of light, how far away is i94 kbbfzlpr o hj1ac 4/dq,+z+t from us?

  Estimate the speed of a galaxy that is 10 billion light.h/* zbeqj4 jh-years away.

  Estimate the observed wavelength for the 656 nm line in the spectrum of a star wg k:d +qx 0*1xvvng2s0 ;vyjnohich is 100 million light-years fr1kqvdj;o+x vnvx02n0: gysg* om us.

  About 1 ms after the Big Ban1co2n l (az01vy- r; bb*mgrrovz9- sgg, the temperature of the universe was about 1013 K. What energy (in eV) does thsyzb*o1vgc 2a9nv o1-r;b m(-z 0grlr is correspond to?