SUHAIL (Lamda Velorum). Amidst the blue-white sparkle of the hot
massive stars of Canis Major and tri-
parted Argo (the Ship) lie a few cool
reddish jewels, the brighter ones Pi
Puppis and Suhail, the latter helping outline the Ship's sails,
the constellation Vela. The ancient Arabs
used "Suhail" as a prefix for the names of a number of southern
stars, including Canopus and Regor (Gamma Velorum), which was originally
known as "Al Suhail al Muhlif, "Suhail of the Oath." With
"Suhails" applied to a variety of stars, the name was eventually
transferred exclusively to the star is now called "Lamda."
Prominent at second magnitude (2.21), this orange class K supergiant (K4, and perhaps
more properly classified as a "bright giant"), is also an
"irregular variable" that wobbles erratically between magnitudes
2.14 and 2.21, a variation only barely sensible to the human eye.
From a distance of 575 light years, it radiates around 11,000 solar
luminosities (including a small correction for absorption by
interstellar dust) from a cool surface whose temperature is
estimated to be around 4000 Kelvin. The combination of luminosity
and temperature gives a radius 207 times that of the Sun, which is close to the size of the Earth's
orbit, the term "giant", even "supergiant," apt indeed. These
parameters also tell of a star of 9 to 12 solar masses (depending
on the exact state of evolution) that seems to be fusing helium
into carbon in its deep core. Stars this massive do not live very
long, Suhail's age estimated at 15 to 30 million years. Suhail is
at or just above the limit at which stars explode. If it does not
blow up as a supernova, it
will turn into some kind of massive white dwarf, perhaps one
made of neon and oxygen rather than becoming one of the more
ordinary carbon-oxygen variety, which is the fate of lower mass
stars like the Sun. Suhail is also beyond a limit for which stars
have magnetically heated sunlike hot outer coronae, and is instead
possessed of a slow wind that blows at a mere 40 to 60 kilometers
per second, under a tenth the speed of the "fast solar wind." The
origin of the wind is not well understood, and may be a combination
of magnetic action and of the star's great luminosity.