Sky & Telescope - December 2023 - 45

Evenings with the Stars by Fred Schaaf
Bright Orion Sights
Winter's mighty Hunter is a sight to behold.
A
s cold weather arrives in the Northern
Hemisphere, a brigade of stellar
brightness climbs into the evening
sky. Let's focus our attention on the
many naked-eye splendors found in the
brightest constellation of this (or any)
season: Orion, the Hunter.
Before diving into Orion's individual
delights, take a moment to appreciate
the main pattern of the constellation
as a whole. It includes two stars
of 1st magnitude and five more of 2nd
magnitude. The Hunter is delineated
by a stellar duo that marks his flaming
shoulders, a second pair of stars that
indicate his radiant knees, three stars
in a row that represent his Belt, and the
collections of fainter lights that outline
the Sword hanging from his Belt.
One of Orion's finest sights is the
fire-colored variable star Betelgeuse,
Alpha (α) Orionis. It's among the
brightest orange stars in the heavens,
but if you've been following the night
sky closely over the past few years, you'll
recall its recent spectacular fade. Starting
in October 2019, Betelgeuse dimmed
from its normal magnitude +0.5 to as
faint (by my estimate) as 1.8, before
brightening to normal again last April.
This sudden dramatic activity doesn't
necessarily indicate that the red supergiant
is about to become a brilliant supernova.
However, most astronomers think
that is likely to happen within the next
100,000 years, which is actually " very
soon " on a cosmological time scale. The
lesson is clear: Keep watching!
Orion's second fascinating bright
star is Rigel, Beta (β) Orionis. Despite
its Beta designation, it shines steadily
at magnitude +0.1, which means it's
almost always slightly brighter than
Alpha Orionis. However, the two stars
have markedly different colors - Rigel
has a touch of blue, which most people
find obvious when shifting their gaze
between it and Betelgeuse.
And supergiant
Rigel is vastly more luminous.
If the two suns were
the same distance from
Earth, Rigel would shine
four times brighter than
Betelgeuse! They only
appear similarly bright
because Rigel is nearly
twice as far away.
One of Orion's most
distinctive features is its
Belt. This trio of equally
spaced, 2nd-magnitude
stars forms an almost
straight line only 3° long.
Scanning east to west,
the Belt is delineated by
Alnitak, Alnilam, and
Mintaka - also known as
Zeta (ζ), Epsilon (ε), and
Delta (δ) Orionis, respectively. Mintaka
holds the distinction of being the
brightest star near the celestial equator,
situated less than ½° south of that
imaginary line. And because the Belt is
so near the celestial equator, from many
latitudes it appears vertical when it rises
due east on December evenings.
The region surrounding Orion's Belt
is peppered with fainter stars, a handful
of which lie at the threshold of nakedeye
visibility under dark skies. Binoculars
will reveal dozens of these gems - a
collection cataloged as the huge open
cluster Collinder 70.
Of course, no discussion of Orion
would be complete without mention of
his Sword, shining " like burnished stellar
steel, " as legendary deep-sky observer
and Sky & Telescope columnist Walter
Scott Houston described it. Compared
to the Belt, however, the Sword is less
distinct - its brightest star is 3rd-magnitude
Iota (ι) Orionis. And as wondrous
as this compact, north-south collection
pWINTER WONDER December evenings
herald the arrival of winter's most distinctive
constellation - Orion, the Hunter. Home to
seven stars of 2nd magnitude or brighter, Orion
stands out boldly even amid the season's array
of bright constellations, including the night
sky's brightest star, Sirius, at lower left.
of stars is, its fame is mostly due to the
presence of the splendid Orion Nebula,
M42. Although the nebula is visible
without optics, its true magnificence is
reserved for telescope users.
Let's conclude our brief survey of
Orion with another recollection from
Scotty as he gazed up at the winter
sky: " How can a person ever forget the
scene . . . it may well be beauty in its
purest form. "
¢ FRED SCHAAF began his first Sky &
Telescope column with a lyric from the
Jethro Tull song " Orion " : " Your faithful
dog shines brighter than its lord and
master / Your jeweled sword twinkles as
the world rolls by. "
sk yand tele scope .o r g * DECEMBER 2023 45
ALAN DYER
https://skyandtelescope.org/
Sky & Telescope - December 2023

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