BETA CAM (Beta Camelopardalis).
Camelopardalis, the Giraffe, a
huge "modern" northern constellation invented only about 400 years
ago, is so obscure that no star within it carries a proper name,
and only three carry Greek letter
names. Only four of its stars are even as bright as fourth
magnitude, the brightest, Beta Camelopardalis, in the middle of the
range (4.03). Nobody points out the dim figure at astronomy open
houses. Yet the ghostly Giraffe is not without its highlights, one
of which is its luminary, Beta. This great star looks faint only
because of its large distance of 1000 light years. In truth it is
a class G (G0) yellow-white supergiant (though of a somewhat
fainter variety) that shines with a luminosity 3300 times that of
the Sun from a surface just a bit cooler
than solar (about 5500 Kelvin) that would stretch three-tenths of
the way from the Sun to the Earth. The star is far enough away,
and close enough to the Milky Way, that it is dimmed some 15
percent by interstellar dust. With a mass around 7 times that of
the Sun, Beta Cam is only around 40 million years old. Lying just
over a minute of arc away is a companion that is itself double,
about which nothing is known except that the brighter is class A,
the dimmer probably F. Separated by at least 25,000 Astronomical
Units, the small double takes at least a million years to orbit the
supergiant (which from the little double would shine with the
brightness of four full Moons). Beta Cam is also a double mystery.
It is most likely making the transition from being a hydrogen
fusing dwarf (of hot class B) to a larger helium-fusing red giant.
Whatever its status, it falls into a zone of temperature and
luminosity in which stars become unstable and pulsate as Cepheid
variable stars (like Mekbuda in Gemini, and even Polaris). Beta Cam, however (like Draco's Rastaban and some others), does not vary,
though some multiple pulsations are present with periods of tens of
days. No one knows why the star is so stable. But is it? During
aircraft observations of meteors in 1967, Beta Cam was seen
suddenly to flash, brightening by about a magnitude over only a
quarter of a second. A variety of "flashes" have been seen from
two dozen stars, including Enif (Epsilon
Pegasi) and Cursa (Beta Eridani).
Beta Cam is an X-ray source, suggesting some kind of solar-like
magnetic behavior, and perhaps the star popped something akin to a
solar flare. So keep your eye on the celestial Giraffe (if you can
find it!).