The Caldwell Objects

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the Pleiades, no particular star in
the Hyades has been assigned a
particular classical name. This
mystery cannot be solved by intuition,
since the Hyades contains 11
stars brighter than magnitude 4.5
and some two dozen stars brighter
than 6th magnitude. Nevertheless,
unless a passage can be found in
classical literature that assigns specific
names to specific stars, we will
have to rely on our imaginations.
For instance, five "stars" (some are
doubles or triples) in the celestial V
have Greek letters: Alpha (α),
Gamma (γ), Delta (δ), Epsilon (ε),
and Theta (θ) Tauri. So we could
(for fun) name four of the five
Greek-lettered stars as follows:
Alpha as Aesula or Ambrosia;
Delta as Dione, Epsilon as Eudora,
and Theta as Thyene. Ovid used
Thyone when he referred to the
whole group.
In Roman times the Hyades
were also called Sidus Hyantis, the
Rain-Bringing Stars. The phrase refers to the
legendary grief the Hyades felt over the death
of their terrestrial half-brother, Hyas; the sisters'
tears were so profuse that they caused
heavy rainfall on Earth. Here we can see how
the Hyades became a bad omen for farmers and
sailors. That myth no doubt refers to the
ancient rising of the Hyades during the
Mediterranean region's rainy season, when
storms raged on land and sea.
Today we associate the rising of the
Hyades with brisk winter nights. The warm
orange light of the giant star Aldebaran
punctuates the tip of the V's southeastern
branch. Aldebaran — from the Arabic word al
dabaran, "the follower" [of the Pleiades] — is a
gentle giant; its
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diameter is only some 40 times that of our Sun.
By contrast, the M-type supergiant star Antares
in Scorpius is 880 times larger than our Sun, and
Orion's Betelgeuse spans 770 solar diameters.
(Note, though, that the diameter of a supergiant
star is a fuzzy concept, since it varies strongly
with wavelength; the supergiants were measured
by laser inventor Charles Townes and his
colleagues at a midin-frared wavelength of 11
microns.) Like other giants of its class, Aldebaran
varies slightly in brightness, from about
magnitude 0.75 to 0.95. The orange giant travels
through space with a 13th-magnitude red-dwarf
companion 31" to the east-southeast. (Be careful
to not confuse Aldebaran's true companion with
an 11th-
Deep-Sky Companions: The Caldwell Objects