Sky & Telescope - January 2021 - 45

Evenings with the Stars by Fred Schaaf

Orion's
Magniﬁcent
Seven
Winter's best-known
constellation is also its
brightest.

A K IR A FUJII

experienced my ﬁrst evenings with the
stars - that is, real outings of marveling and learning - in the winter in
which I turned six years old. The ﬁrst
constellation I discovered that winter is
still my favorite. It's also the one that
almost everyone considers ﬁnest of all:
Orion the Hunter.
The brightest constellation. There
are only two constellations other than
Orion that contain two stars of 1stmagnitude or brighter. These are the farsouth groupings Centaurus (the Centaur) and Crux (the Southern Cross).
But neither of these has the visual
appeal of Orion. Crux is very small, and
its cross shape lacks the crucial middle
star. The main pattern of Centaurus
contains many rather bright stars but is
large and sprawling. In contrast, Orion's
seven principal stars include +0.2-magnitude Rigel, +0.4-magnitude (usually)
Betelgeuse, and ﬁve stars of roughly 2nd
magnitude: Bellatrix, Alnitak, Alnilam,
Mintaka, and Saiph. Together, they
make Orion the most concentratedly
brilliant constellation of all.
Compare Orion's seven stars to the
same number making up the Big Dipper. This extremely famous asterism (an
unofﬁcial pattern of stars) contains
no suns of 1st magnitude or brighter, a
half-dozen 2nd-magnitude lights, and
a single 3rd-magnitude star. Of course,
the Big Dipper catches our attention
because it so closely resembles such a
well-known implement, a pan or ladle.
But Orion represents the most familiar
and interesting of all shapes to us: the
human body.

WINTER LIGHTS Orion the Hunter stands out even amongst the many bright stars of the
winter sky. The constellation's distinctive three-in-a-row Belt, along with Betelgeuse and
Rigel, make it easy to identify.

Contrasting Betelgeuse and Rigel.
No other constellation's brightest two
stars provide so strong a color contrast
as blue-white Rigel and orange-yellow
Betelgeuse. Most people can notice the
difference in these hues by glancing
back and forth between the stars with
the naked eye.
This month also provides the
unusual opportunity to compare the
colors of Betelgeuse and Mars. As our
star chart (on pages 42-43) shows,
both objects are visible together during
evening hours. What's more, the Red
Planet is currently in the same brightness range as Betelgeuse.
I've called both the star and the
planet "campﬁre-colored." Robert
Burnham, Jr., in his classic Burnham's
Celestial Handbook, used a different
descriptor. He wrote, "The exotic word
padparadscha, used in India to designate
the rare orange sapphire, might be an
appropriate name for Betelgeuse."
The only ﬁrst-magnitude star that
varies greatly in brightness. Amazingly, last winter Betelgeuse unexpectedly dimmed so much that some

observers estimated it to be as faint as
magnitude 1.8. That's very slightly dimmer than the Hunter's other shoulderstar, Bellatrix, and two of the stars in
his Belt. But historically Betelgeuse may
also have been uncharacteristically
bright at times. The great astronomer
John Herschel wrote in December 1852
that Betelgeuse was then "the largest
star in the northern hemisphere." In
this context, "largest" meant "brightest," suggesting a magnitude of -0.1 or
better - equalling golden Arcturus in
Boötes. Former Sky & Telescope editor in
chief Joseph Ashbrook also estimated
Betelgeuse to be magnitude -0.1 at its
most luminous during a period spanning 1937 to 1975.
Orion on the meridian. The blazing
stars of Orion are near the meridian
around 9 p.m. at month's end. Remarkably, the second and third brightest
stars of winter (Capella, in Auriga, and
Rigel, respectively) transit the meridian
at almost exactly the same time.
FRED SCHAAF welcomes your letters
and comments at fschaaf@aol.com.
sk yandtelescope.org * JANUARY 2 021

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