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.
Written by Jim Kaler. Return to STARS.