119 TAU (119 Tauri=CE Tauri). Number 119 from Flamsteed's old list, the star
is really better known by its variable star name of CE Tauri. Of
fourth magnitude, 119 Tauri inhabits southeastern Taurus directly above Orion.
It may appear anonymous among the many stars surrounding the Taurus-Auriga star-forming dark cloud. It
is however, a rare thing, a class M (M2) supergiant, one of the few
in the naked-eye sky, one much like Betelgeuse in Orion, only much farther
away, at distance of some 1900 light years. Moreover, though it is
on the periphery of the dark cloud, it is still affected by
intervening dust, which dims the star by 0.8 magnitudes, a factor
of two. The measured distance is also subject to significant
error, the range falling between 1300 and 3600 light years, so the
stellar characteristics are not all that well known. Temperature
and correction for infrared light also add uncertainties. No
matter what, it is a magnificent star. For a temperature of 3500
Kelvin, the luminosity radius, and mass come out to be 82,000
solar, 800 solar radii (3.7 Astronomical Units, 70 percent the size
of the orbit of Jupiter), and 18 solar masses. A more reasonable
3700 Kelvin suggests 47,000 solar luminosities, 525 solar radii
(2.4 AU), and 12 to 15 solar masses. Even these numbers are huge.
Also like Betelgeuse, and like most huge stars, 119 Tau is variable
(hence the name CE Tau), except whereas Betelgeuse is irregular in
its variations, 119 = CE is a "semi-regular" pulsator that changes
by roughly 0.3 magnitudes over a period of about 165 days. The
star is curiously metal-rich, its iron content (relative to
hydrogen) 30 percent greater than that found in the Sun. 119 Tauri
is most likely fusing its internal helium into carbon, although a
more advanced state of carbon fusion (to neon, magnesium, and
oxygen) cannot be ruled out. Such stars are rare because they
evolve from rare hydrogen-fusing O stars like those that dot Orion.
Its fate is almost certainly to explode as a supernova. Though unlikely,
it could even go off tonight: better, just keep your eye out over
the next million or so years.