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 four of them. None
have proper names. The second brightest does not even carry a
traditional name, only a catalogue number, the top six Beta 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 "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.