After making that picture of the brightest stars by their luminosity or quantity of light (as opposed to their “magnitude”), I realized that I could have arranged it more instructively in two columns like this:
The stars in the left column are all in the southern hemisphere of the sky; those on the right are the brightest stars of the north. (The figures after each star’s name are its magnitude and its light as a fraction of Sirius’s.)
Fred Schaaf had remarked in his Sky & Telescope article that it would take the combined light from Arcturus, Vega, and Capella – the three brightest north-hemisphere stars – to match that of Sirius. (We found that it would actually take more.) But those three do not even rank next after Sirius; there are two other south-hemisphere stars above them, Canopus and Alpha Centauri.
So a part of the point is that the southern hemisphere happens to be richer in very bright stars than the northern. Since our culture developed in the north, we don’t even have traditional names for some of those deep-south luminaries, Alpha and Beta Centauri and their neighbors Alpha and Beta Crucis. (Names have been concocted for them, Rigilkent, Hadar, Acrux, and Mimosa, but we can scarcely remember those and we keep referring to them by the Greek-letter designations. Many people have heard that Alpha Centauri is the nearest star to us.)
I’ve made my program add up the luminosities of the stars in terms of Sirius’s. The 12 southern stars (including Sirius) add up to 2.9 Siriuses of light, while the 11 northern stars amount to only 1.595 Siriuses. (Sirii, I suppose I should say.)
Of course the statistics depend on where we make the cut for our list of “brightest” stars, and I’ve used the convenient cutting-point of magnitude 1.6, giving a list of 23. The southern hemisphere happens to be richer in these few very bright stars, but that is just because of the chance of where the very few very brightest happen to be. If we were to include dozens more of the fainter stars, or hundreds, or thousands, their individual contributions of light would be increasingly tiny, but presumably the totals of starlight for the hemispheres would come to be about equal. The only overall inequality in amount of starlight is between the Milky Way and the rest of the sky.
Instead of columns, why not arrange these luminosity symbols on a map?
Because of the range of sizes of our symbols, some fall on top of others, especially in the bunches in the Orion region and the Crux region, both of which are in or near the Milky Way.
I thought this might be an alternative way of symbolizing stars for star maps in general, but it wouldn’t really work.
If for instance you wanted to draw a map of an area including stars down to magnitude 8 (like Neptune) and also including Sirius, you’d have to make the squares for the faintest stars at least say 1 square millimeter in size; and then the square for Sirius would have to be about 6000 square millimeters – that is, 77 millimeters (3 inches) on a side – inconveniently huge. This illustrates why we use our logarithmic scale of magnitudes instead.