The appearance of thex1v+ +oiufsmo** q ,wi great range of brightness among stars is due to

  The absolute luminosit7fehp jd(mah+ w58:u i wy4nz)y for most stars depends on the

  Four different main-sequence stars are colored blue, orange, r0i)29en qgb peed, and yellow. What is their rank from coolest to hottestnq0i9g2be ) ep?

  A Hertzsprung-Russell diagram shows stars dsl sfb))v.u( em ;,mus+j.jv on a plot of

  A white dwarf star with a mass equal to that of the Sun is abo78 99x ud9urdeta; *ijiajn ,xut the size of

  The Chandrasekhar limit of stellar mass (below m,.2 9x-alrp8 qysjkzb ixpc40;1r nwwhich a star will collapse into a white d1p4qr pczbk9jw2yx ;xrn.0 ai 8s-,mlwarf) is, if the mass of our Sun is M, about

  Supernovas are thought to alwayx/35 ns(zz ovgs result in

  Black holes

  Pulsars are rapidly spinn)mctcq k -c2chgtw*7.ing

State Einstein's principle of equi,-5*og,lj1k (z 6ztq d tuol ft2oa7bbvalence.

  The Schwarzschild radius of a black hole is thatb* v+arh yhr6 qwd9*i: radial distance from the center of a sphere within which not even light can escape.wdr**ahhy r69b:+v qi 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 particular wavelength in the visible, andbf9tv;x(4kacwqa 6 z2 t2v(6;4ca wzkx qbtaf 9he source is moving away from us, the color of the light appears to us to be shifted toward the

  The cosmic background radiation corresponds to a tem;. n2ie ilt(v;/pxlayperature of about

  The Sun has apparent5v:vj j -vgh 6ag-o0dvk5 aoo-sj7ns+ brightness 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 lumi2dg 7;gzpp,m1gkohyw3n ( q 5hnosity 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 mean radius xe j32 qumkw 14y*uhjz* e8.ono +ccf/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 radiusq j rivnr, ) c9z.oz)acof5o:l6k2r4s 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'u12zgm:xcw 3z s nearest star at mu3cxwz:1 z 2g4.3 ly?

  The apparent brightness of a s:c5np 4fxm 5+ a9gxikotar 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 universb-r 5q+4 n0ar eni(4-a.qv tvtfeu,nb e is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estiivv4.far(rnuqee- q t,tn 5b b+4a 0-nmate the age of the universe, in years.

  If a galaxy is moving away from us at yu4;yzukh, ,(-9ozy vhgzi (i1.0% of the speed of light, how far away is it from iozghu z yzh(yy,v(, ui;94-kus?

  Estimate the speed of a galaxy that is 10 billion light-years awaydzxu.r2)*9bo.7rosn 6ln7m 4 w ykob t.

  Estimate the observed wavelength for the 656 nm0j1ul3hf3i x l line in the spectrum of a star which is 100lu31 il0hj3xf million light-years from us.

  About 1 ms after the Big Bang, the teh vijgtb )/.+qgvi** emperature of the universe was about 1013 K. What energy (*vg v+bij )q*eg.hit/ in eV) does this correspond to?