Sky & Telescope - February 2021 - 45

Evenings with the Stars by Fred Schaaf

In Praise
of Procyon
Alpha Canis Minoris is a
serious underdog.

A K IR A FUJII

rocyon is the one bright star in
Canis Minor, the Little Dog. It's
often called the Lesser Dog Star because,
at magnitude +0.4, it shines two full
magnitudes fainter than the night sky's
most brilliant star, Sirius, the Dog Star
in Canis Major, the Big Dog.
Procyon suffers in almost every
category of comparison with neighboring Sirius. But the Lesser Dog Star has
many of its own merits, including its
fascinating position both on star maps
and in space.
Terriﬁc tip of the tail. Procyon is
the eighth brightest nighttime star and
sixth brightest visible from latitude
40° north. It also utterly dominates its
constellation, though that's not difﬁcult considering Canis Minor has only
two additional stars brighter than 5th
magnitude within its borders. The Little
Dog is usually pictured on star charts as
a single short line connecting Procyon
to Gomeisa (Beta Canis Minoris),
which glows modestly at magnitude
2.9. The two-star line is more like a
dog's tail than a whole dog. And since
Canis Major and Canis Minor face west
as they follow Orion, Procyon can be
thought of as the brilliant tip of the
Little Dog's tail.
Procyon's part in sky patterns.
Procyon is accompanied by numerous
bright stars as it climbs high in the sky
on February evenings. Amazingly, this
region contains nine of the 15 brightest stars visible from mid-northern
latitudes. Much of Procyon's beauty is
due to its placement within two large
patterns of bright winter stars.
Check our star map (pages 42-43)
to trace out the giant asterisms known
as the Winter Hexagon and the Winter

S HUNTER AND DOGS Mighty Orion is trailed by his faithful companions, Canis Major and Canis
Minor. The winter Milky Way flows between brilliant Sirius (lower left) and Procyon (upper left), and
just north of golden-orange Betelgeuse.

Triangle, both of which include Procyon. The Winter Hexagon is formed
by connecting Aldebaran, Capella,
Pollux (along with Castor sometimes),
Procyon, Sirius, Rigel, and back to
Aldebaran, with orange-gold Betelgeuse
roughly in the middle of the Hexagon.
The Winter Triangle comprises Sirius,
Betelgeuse, and Procyon. This latter
asterism is an almost perfect equilateral
triangle. Procyon is 26° from Betelgeuse
and 26° from Sirius, while Sirius is 27°
from Betelgeuse. Remarkably, Procyon is
a similar distance from two more bright
stars - it's 27° from Castor and 23°
from Pollux.
Most amazingly, Procyon is very
nearly due east of Betelgeuse and due
south of Pollux. Betelgeuse is 7.4° north
of the celestial equator, but Procyon
is 5.2° north of that key line - closer
than any other 1st-magnitude or
brighter star. In last month's column
we noted that Capella is almost exactly
due north of Rigel. Similarly, Procyon is
positioned due south of Pollux and just
a hair (1/10°) farther west.
Procyon's place in space. Both
Dog Stars are among the nearest stars

to Earth. Procyon's distance is 11.5
light-years, while Sirius is 8.6 lightyears away. Another interesting aspect
of the previously noted Procyon-Pollux
connection is that Pollux is 33.8 lightyears away - almost exactly three times
farther than Procyon.
But what is especially interesting about Procyon's place in space is
illustrated by considering the appearance of familiar stars as viewed from
Procyon. For example, our Sun would be
a 2.5-magnitude star in southern Aquila
in the Procyonic sky. Nearby Sirius,
situated 5.2 light-years from Procyon,
would gleam at about magnitude -2.5,
and Procyon's white dwarf companion would shine brighter than the full
Moon! Remarkably, a red dwarf called
Luyten's Star is only 1.2 light-years from
Procyon yet wouldn't be bright enough
to see with the naked eye. But, as seen
from Luyten's Star, Procyon would
dazzle at around magnitude -7!
FRED SCHAAF started writing his first
book, Wonders of the Sky: Observing
Rainbows, Comets, Eclipses, the Stars
and Other Phenomena, 40 years ago.
sk yandtelescope.org * FEBRUARY 2 021

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Sky & Telescope - February 2021

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