Sky & Telescope - December 2022 - 45

Evenings with the Stars by Fred Schaaf
Extra
Taurus
Treasures
The constellation is more
than just a couple of clusters
and a bright star.
M
ention Taurus to most stargazers
and they'll immediately think of
the Pleiades and Hyades star clusters,
and Aldebaran, the 1st-magnitude
orange star that marks the Bull's eye.
So wondrous is this constellation that
even though I've already devoted two
columns to it, there's more to discuss!
Aldebaran and the Hyades together
form the tilted V that outlines the Bull's
face, while the Pleiades are located on
his shoulder. But can we trace out the
entire form of the beast? Actually, we
can't. Traditionally, only the front half
of Taurus is outlined with stars. One
explanation for this is that the back half
of Taurus is underwater. The story is
that Zeus, king of the gods, assumed the
form of a bull who carried the maiden
Europa off across the waves.
In addition to the Bull's face, stars
mark his horns, too. The more northerly
horn is tipped with 1.7-magnitude
Beta (β) Tauri, also called Elnath (a
name derived from the Arabic for " the
butting one " ). Although Elnath officially
belongs to Taurus, it's also used
to complete the famous pentagon shape
of Auriga, the Charioteer. So luminous
is the winter sky, however, that
Elnath struggles to stand out from the
crowd. Indeed, just over the border in
Orion we find three more stars that
have essentially the same magnitude as
Elnath: Bellatrix (the star indicating the
Hunter's western shoulder) along with
Alnilam and Alnitak (the two brightest
Belt stars). The four are so similarly
bright that you likely won't be able to
detect any differences among them.
pCHARGING BULL Taurus looks to be in some trouble as he charges headfirst at Orion, who's
poised with his upraised club. Thankfully, in the night sky, both constellations are more likely to
delight stargazers than provoke concern.
But at least Elnath outshines its
counterpart on the tip of the Bull's
southern horn, Zeta (ζ) Tauri. Elnath
is noticeably brighter than Zeta, but
the latter is much closer to the ecliptic
and therefore engages in many more
and closer conjunctions with the Moon
and planets. And Zeta has another
claim to fame. In the summer of AD
1054, a point of light only about 1° to
the northwest dramatically outshone
it. Brighter than the planet Venus, the
" guest star " was observed in broad
daylight by Chinese astronomers for 23
days. Today we know this luminary as
the sky's most famous supernova remnant,
M1, the Crab Nebula. Even today,
poor Zeta plays second fiddle to the
Crab; most telescope users simply regard
the star as a convenient jumping-off
point for the nebula.
This month, the brightest light in
Taurus isn't a supernova or even Aldebaran,
but rather it's another guest: the
planet Mars. As described on page 48,
the Red Planet reaches opposition on
December 8th and spends the entire
month drifting westward across Taurus.
At its peak this month, Mars is 12 times
brighter than Aldebaran, though the two
share a similar ruddy hue. And, in March
2023, the planet will be neatly positioned
between the tips of the Bull's horns.
Let's close with a couple of rarely
mentioned stars in southern Taurus
that form a line leading from Gamma
(γ) Tauri (the tip of the Hyades V)
straight to the head of Cetus, the
Whale. The first star, about 6° southwest
of Gamma, is Lambda (λ) Tauri
- one of the brightest eclipsing variable
stars. It varies modestly from magnitude
3.4 to 3.9 over a period of 3.95
days - a variability first noticed in 1848
by British astronomer Joseph Baxendell.
Continue the line toward Cetus
and you'll find Xi (ξ) and Omicron (ο)
Tauri. These two shine respectively at
magnitudes 3.8 and 3.6 and are a little
less than 1° apart, making them a wonderful
naked-eye double.
¢ With this installment, FRED SCHAAF
completes 30 years of writing columns
to accompany this magazine's central
star chart.
sk yand tele scope .o r g * DECEMBER 2022 45
ALEXANDER JAMIESON / CELESTIAL ATLAS (1822) / UNITED STATES
NAVAL OBSERVATORY LIBRARY / PUBLIC DOMAIN

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Sky & Telescope - December 2022

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