ALPHA CAM (Alpha Camelopardalis). One would hardly think that a giraffe would grace far northern skies, but there it is, Camelopardalis, to the north of Auriga and Capella. Its brightest stars are but fourth magnitude, and at that there are only three of them. None have proper names. The second brightest does not even carry a traditional name, only a catalogue number, the top four Beta Cam (magnitude 4.03), HR 1035 (4.21), Alpha Cam (4.29), and fifth magnitude Gamma (4.63), where "HR" stands for "Harvard Revised" from the Yale Bright Star Catalogue. Alpha Cam, a rare blue-white class O (O9.5) bright supergiant (as found from its spectrum alone), is seemingly faint mostly because it is far away, but also because it is dimmed by nearly a full magnitude by intervening interstellar dust. Indeed, the star is SO far away that we have no actual distance measure of it. For many years the star has been taken as a "runaway" star (rather like Zeta Ophiuchi) from the Cam OB1 association of O and B stars (such "associations" being huge collections of dispersing young stars that were born more or less at the same time from the same birthcloud). In fact it has been taken as a runaway from the associated cluster NGC 1502 (from which it probably would have been kicked by interactions with other stars or by an explosion of a massive companion). The estimated distance of Cam OB1 and NGC 1502 is about 3200 light years, which we might adopt as the distance of Alpha Cam. If so, the luminosity (incorporating the dimming by dust and ultraviolet radiation from a 30,000 Kelvin surface) is a magnificent 530,000 Suns(!), which is almost exactly what we would expect from such a supergiant, meaning that the guessed distance is pretty close to the mark. Alas, the beginning thesis may be wrong. Newer observations show that Alpha Cam is not moving directly away from the cluster. Not only is its motion through space in the wrong direction, but a wake that the star is leaving as it passes through a local interstellar cloud points the wrong way as well (though the cloud might have its own confusing motion). More, recent observations suggest that the Cam OB1 association might not actually be real. Clearly, more research needs to be done. What is real is that this magnificent star, which has a mass between 25 and 30 times that of the Sun, will surely someday explode. At the moment it is losing matter through a powerful wind at a rate of six millionths of a solar mass per year, consistent with the great luminosity and the fate to come. Thanks to José Rodriguez, who suggested this star.
Written by Jim Kaler. Return to STARS.