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ALPHA CAM (Alpha Camelopardalis). One would hardly think that agiraffe would grace far northern skies, but there it is,Camelopardalis, to the north ofAuriga andCapella. Its brightest stars are butfourth magnitude, and at that there are only four of them. Nonehave proper names. The second brightest does not even carry atraditional name, only a catalogue number, the top sixBeta Cam (magnitude 4.03), HR 1035 (4.21),Alpha Cam (4.29), 7 Cam (4.47), and fifth magnitude HR 1040 (4,54)and Gamma (4.63), where "HR" stands for "HarvardRevised" from the Yale Bright Star Catalogue. Alpha Cam, a rareblue-white class O (O9.5) bright supergiant (as found from itsspectrum alone), is seemingly faint mostly because it is far away,but also because it is dimmed by nearly a full magnitude byintervening interstellar dust. Indeed, the star is SO far awaythat we have no actual distance measure of it. For many years thestar has been taken as a "runaway" star (rather likeZeta Ophiuchi) from the Cam OB1 associationof O and B stars (such "associations" being huge collections ofdispersing young stars that were born more or less at the same timefrom the same birthcloud). In fact it has been taken as a runawayfrom the associated cluster NGC 1502 (from which it probably wouldhave been kicked by interactions with other stars or by anexplosion of a massive companion). The estimated distance of CamOB1 and NGC 1502 is about 3200 light years, which we might adopt asthe distance of Alpha Cam. If so, the luminosity (incorporatingthe dimming by dust and ultraviolet radiation from a 30,000 Kelvinsurface) is a magnificent 530,000Suns(!),which is almost exactly what we would expect from such asupergiant, meaning that the guessed distance is pretty close tothe mark. Alas, the beginning thesis may be wrong. Newerobservations show that Alpha Cam is not moving directly away fromthe cluster. Not only is its motion through space in the wrongdirection, but a wake that the star is leaving as it passes througha local interstellar cloud points the wrong way as well (though thecloud might have its own confusing motion). More, recentobservations suggest that the Cam OB1 association might notactually be real. Clearly, more research needs to be done. Whatis real is that this magnificent star, which has a mass between 25and 30 times that of the Sun, will surely someday explode. At themoment it is losing matter through a powerful wind at a rate of sixmillionths of a solar mass per year, consistent with the greatluminosity and the fate to come. Thanks to José Rodriguez, whosuggested this star.
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