Sky & Telescope - March 2024 - 45

Stories in the Stars by Stephen James O'Meara
Betelgeuse
" Inflamed
by Wine "
Is an ancient Greek myth
linked to the variability of
one of the night sky's most
prominent stars?
N
o naked-eye star in the heavens has
drawn so much attention of late as
Betelgeuse, the rosé-colored alpha star
of Orion. Astronomers are debating
whether this aged red supergiant will
erupt as a supernova in the near future
or continue to wax and wane in brilliance
as it has done for centuries. Now
is as good a time as any for you to start
monitoring Betelgeuse's changes. But
first, let's look back in time.
Our story begins with English
astronomer John Herschel, who is
often credited with discovering the
star's variability. Usually Betelgeuse
shines around magnitude +0.5, nearly
as bright as yellow Procyon, Alpha (α)
Canis Minoris. Herschel's observations
of the star from 1836 to 1839
from the Cape of Good Hope, however,
show that Betelgeuse rivalled Rigel
(magnitude +0.2) in November 1836.
In January 1839, it dropped to a low
of 1st magnitude, when it was fainter
than Aldebaran but brighter than Pollux.
By November 1839, Betelgeuse had
rebounded - this time exceeding Rigel.
Herschel thought it " a little extraordinary "
that a periodic variation of
such great extent in a " so very important
and remarkable star " should have
previously gone completely unobserved.
But is that true? Support is growing for
the claim that Indigenous Australians
long ago registered the variability of
Betelgeuse. And one myth hints that the
ancient Greeks had noticed Betelgeuse's
brightness variations.
pROSÉ LIGHT The recovery of Betelgeuse (the bright, reddish star at upper left) from its record
slumber is captured in this pair of images. The one at left was obtained on February 12, 2020,
when the author estimated the star's magnitude at 1.7. The right-hand image captured on April 24,
2020, shows the red giant's return to average brightness, estimated to be magnitude +0.5.
That myth (which might predate the
8th century BC) tells us that when the
handsome giant Orion travelled from
Egypt to the Greek island of Chios, he
fell in love with Merope, the only daughter
of the island's legendary king Oenopion.
All was well until one night, when,
" inflamed by wine, " Orion insulted
Merope. Unable to control his anger,
Oenopion asked Dionysus (god of wine)
to put Orion into a deep sleep. Merope's
father then blinded the giant and cast
him off to sea in a boat. Following the
sound of a Cyclops's hammer, Orion
landed on the island of Lemnos, where
Hephaestus (god of fire) provided Orion
with a guide who led him eastward to
be healed by Sol (the Sun). Upon facing
Sol's rays, Orion's sight returned.
The loss and recovery of Orion's
sight could parallel the fading and
recovery of Betelgeuse, whose wineinfused
hue may have helped inspire
the myth. " Many of the first recorded
wines [in ancient Greece] were rosé,
light libations made by watering down
field blends of combined white and red
grapes, " writes Victoria James in A Brief
History of Rosé, an online article for
GuildSomm International. The link is at
least an alluring possibility.
Just as Orion was a giant among
humans in myth, Betelgeuse is a giant
among stars in reality. This red supergiant
star is 1,500 times larger than
our Sun. And though it lies some 500
light-years distant, it generally shines
as the ninth-brightest star in the night
sky. The star's redness, however, makes
estimating its magnitude a challenge,
as our dark-adapted eyes are sensitive to
red light - the longer we stare at Betelgeuse,
the brighter it seems. One way
to combat this problem is to use quick
glances when gauging its brightness.
To make an estimate, start by selecting
two comparison stars that appear
closest to it in brightness (one brighter,
one fainter). The best comparison stars
near Betelgeuse are Capella (magnitude
+0.1) in Auriga; Procyon (+0.4) in Canis
Minoris; Aldebaran (+0.9) in Taurus;
Pollux (1.1) in Gemini; and Bellatrix
(1.6), also in Orion.
Although Betelgeuse was born
only 10 million years ago, it may have
already used up its energy supply and
gone supernova. We don't know for
sure, because we see the star as it was
500 years in the past. If Betelgeuse has
already exploded, we might be lucky
enough to see it brighten magnificently!
¢ Contributing Editor STEPHEN JAMES
O'MEARA has been studying the stars
and their lore for more than 50 years.
sk yand tele scope .o r g * MARCH 2024 45
STEPHEN JAMES O'MEARA (2)

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Sky & Telescope - March 2024

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