ALBALI (Epsilon Aquarii). As for so many stars, the significance
of its proper name is lost to time. From an Arabic word meaning
"Swallower," the title of this fourth magnitude (3.77) star in Aquarius descended from a separate obscure
phrase, and originally referred to the trio of stars we now know as
Epsilon, Nu, and Mu Aquarii. Together, they represented an Arabic
"lunar mansion," a sort-of zodiacal sign. The name was then later
placed on Epsilon alone. Well off the main-stream part of
Aquarius, far to the southwest of the constellation's "Water Jar," Epsilon Aquarii (as well as Mu
and Nu Aquarii) lies just above the northwestern corner of Capricornus. While Albali (an A1 dwarf,
though sometimes called A1.5) is of the same class as Sirius , it is much farther (230 light
years, as opposed to Sirius's 8.6) and five or more times more
luminous. Exactly how much more depends on which of the discordant
temperatures on adopts to account for ultraviolet radiation (which
range from 9050 Kelvin to 11,200 K). The average of 9670 K leads
to a luminosity of 145 solar luminosities, while a lower average
calculated by tossing the highest value gives 9160 Kelvin and 132
Suns' worth of power,
really not all that much different. Yet it
shows the uncertainty that attends a large variety of stars. Radii
then respectively come in at 4.2 and 4.6 solar, masses between 2.8
and 3.2 solar depending on the temperature and the exact state of
evolution, which, no matter what the case, is close to the end of
core hydrogen fusion, perhaps rendering the star more a subgiant.
With a projected equatorial rotation period of 100 kilometers per
second, Albali star rotates in under 2.3 days. Listed as
"suspected of variability," no one actually seems to claim that the
star is in any way unstable. Consistent with the temperature
uncertainties, one source suggests the star to be metal-rich, while
another shows it to be of more or less solar composition with some
deficiencies. Part of the problem might be contaminant light from
a purported companion, but one that has never confirmed. While no
planets have been found, Albali does seem to have some sort of debris
disk that radiates infrared light. If
nothing else, Albali, true to its name, is confused and confusing.
(Thanks to Paolo Colona, who suggested this star.)
Written by Jim Kaler 10/03/08. Return to STARS.